Valid Fri Apr 26, 2024
Valid Sat Apr 27, 2024
Valid Sun Apr 28, 2024
+ Additional Links
- » Description of the National Forecast Chart
- » Product Archives
- » Download hazards in KML or shapefile format or GeoJSON format
NWS Weather Prediction Center College Park MD
402 PM EDT Fri Apr 26 2024
Valid 00Z Sat Apr 27 2024 - 00Z Mon Apr 29 2024
...There is a Moderate Risk of excessive rainfall over parts of the
Central/Southern Plains on Saturday...
...Heavy snow over the Central Rockies...
...There is an Enhanced Risk of severe thunderstorms over parts of the
Middle/Lower Mississippi Valley and Central/Southern Plains...
Low pressure over Central Plains will move northeastward into East-Central
Canada by Sunday morning. A second low develops over the Southern High
Plains by Saturday morning and likewise, move northeastward to the Middle
Mississippi Valley by Sunday. Showers and severe thunderstorms will
develop east of the dryline. Therefore, the SPC has issued an Enhanced
Risk (level 3/5) of severe thunderstorms over the Middle/Lower Mississippi
Valley and Central/Southern Plains through Saturday morning. The hazards
associated with these thunderstorms are frequent lightning, severe
thunderstorm wind gusts, hail, and a few tornadoes. In addition, there is
an increased threat of EF2- EF5 tornados and hail greater than two inches
over the Region.
Moreover, heavy rain will be associated with these storms. Therefore, the
WPC has issued a Slight Risk (level 2/4) of excessive rainfall over the
Middle/Lower Mississippi Valley and Southern Plains through Saturday
morning. The associated heavy rain will create mainly localized areas of
flash flooding, with urban areas, roads, small streams, and low-lying
areas the most vulnerable. Heavy snow will develop over the higher
elevations of the Central Rockies overnight Friday into Saturday.
On Saturday, the threat of severe thunderstorms continues, while the
threat of excessive rainfall increases over parts of southeastern Kansas,
southwestern Missouri, Oklahoma, and northeast-central Texas. Therefore,
the SPC has issued an Enhanced Risk (level 3/5) of severe thunderstorms
over the Middle Mississippi Valley and Central/Southern Plains from
Saturday into Sunday morning. The hazards associated with these
thunderstorms are frequent lightning, severe thunderstorm wind gusts,
hail, and a few tornadoes. In addition, there is an increased threat of
EF2- EF5 tornados and hail greater than two inches over the Region.
Furthermore, heavy rain will be associated with these storms. Therefore,
the WPC has issued a Moderate Risk (level 3/4) of excessive rainfall over
parts of the Middle Mississippi Valley and Central/Southern Plains. The
associated heavy rain will create numerous areas of flash flooding.
Furthermore, many streams may flood, potentially affecting larger rivers.
On Sunday, the threat of excessive rainfall decreases slightly. Therefore,
the WPC has issued a Slight Risk (level 2/4) of excessive rainfall over
the Middle/Lower Mississippi Valley and Southern Plains on Sunday. The
associated heavy rain will create mainly localized areas of flash
flooding, with urban areas, roads, small streams, and low-lying areas the
most vulnerable.
Similarly, the threat of severe thunderstorms decreases slightly on
Sunday, too. Therefore, the SPC has issued a Slight Risk (level 2/5) of
severe thunderstorms over parts of the Middle/Lower Mississippi Valley and
Central/Southern Plains on Sunday. The hazards associated with these
thunderstorms are frequent lightning, severe thunderstorm wind gusts,
hail, and a few tornadoes.
Meanwhile, upper-level troughing over the western third of the country and
onshore flow will produce rain and high elevation snow over parts of
Pacific Northwest, California, Great Basin, Northern Intermountain Region,
and Southwest through Saturday morning. The low elevation rain and higher
elevation snow continues over parts of the Northern/Central Rockies
through late Saturday night. On Sunday, the rain and higher elevation snow
returns to the Pacific Northwest.
Ziegenfelder
Graphics available at
https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php
NWS Weather Prediction Center College Park MD
301 PM EDT Fri Apr 26 2024
Valid 12Z Mon Apr 29 2024 - 12Z Fri May 03 2024
...Potentially severe thunderstorms and heavy rain causing flash
flooding are forecast to continue in the Lower Mississippi Valley
Monday...
...Overview...
Upper troughing will support a surface frontal system with
widespread thunderstorms ahead of it across the central U.S. into
Monday. Heavy rain is likely to cause flash flooding in the Lower
Mississippi Valley in particular, while severe weather may also be
a threat. The upper pattern looks to become more zonal after the
early part of the week, with increasing uncertainty in
shortwave/embedded upper low details and surface specifics from the
Pacific eastward. For the Lower 48 there is at least a general
theme of a leading system followed by another frontal system
affecting the central-eastern U.S. by the latter half of the week,
with both serving to focus areas of showers and thunderstorms.
There is still a lot of uncertainty over the Northwest by late next
week though. Near to above normal temperatures should prevail over
much of the East into at least the southern half of the Plains
through Intermountain West, while the Northwest and possibly other
northern tier areas may see one or more days of below normal highs.
...Guidance/Predictability Assessment...
Recent variability/trending and spread in the guidance leads to
below average confidence in some important aspects of the forecast
next week. Through the 00Z/06Z cycles, there were essentially two
primary layers of uncertainty. The first involves the trough/upper
low(s) over the Northwest U.S. and British Columbia as of early
Monday. Over the past day or so the GFS/ECMWF and their ensemble
means have trended toward greater progression of this feature whose
energy could ultimately split into two pronounced upper troughs
and/or lows. In contrast, the 00Z UKMET/CMC-CMCens clustered with
what had been the prior consensus of holding the initial feature
back near the Pacific coast while awaiting input from upstream
Pacific energy. 00Z ECMWF-initialized machine learning models (MLs)
agreed upon the more progressive theme, thus recommending
exclusion of the 00Z UKMET/CMC from the forecast. However the MLs
suggested that the upper energy could be more consolidated into one
upper low (located near the northern High Plains as of early
Wednesday) versus what the GFS/ECMWF were showing.
Beyond this discrepancy, guidance diverged even more with respect
to Pacific/western U.S. flow later in the week. ECMWF runs and the
00Z GFS along with the GEFS/ECens means brought a trough/possible
compact upper low into the Northwest (with a lot of spread among
individual ensemble members), but a slight majority of the MLs
actually built a ridge over the West Coast by late week due to
greater troughing over the Pacific near 140-150W. The 06Z GFS
trended that way too, deflecting the late week upper low farther
north into Canada.
In light of guidance differences, ML suggestions, and continuity,
the updated forecast used a blend of 00Z and 12Z/25 ECMWF runs and
the 00Z/06Z GFS early in the period followed by a 40-50 percent
weight of the 06Z GEFS/00Z ECens means with lingering weight of
those GFS/ECMWF runs mid-late period. This solution yielded only
minor nudges from continuity in this lower predictability regime.
In the new 12Z guidance, the UKMET/CMC have trended significantly
toward other dynamical guidance for progression of the initial
Northwest U.S./British Columbia feature. This still leaves a
difference between the dynamical solutions and more consolidated
MLs. The CMC/UKMET also favor higher heights along the West Coast
by late week while the GEFS mean still brings in a modest trough.
...Weather/Hazards Highlights...
Ample moisture and instability will be present across much of the
central U.S. into Monday ahead of a Plains upper trough and
associated surface frontal system. The most likely focus for the
heaviest convection and rainfall is across the Lower Mississippi
Valley, where a Slight Risk is maintained in the Monday/Day 4
Excessive Rainfall Outlook. This may be a higher-end Slight Risk if
the heaviest model QPFs of 3-5 inches with rain rates over 2
inches per hour end up verifying. By Tuesday the upper-level
support will likely weaken, so overall expect lower rainfall
amounts and rain rates. However, some additional convection could
develop within an area of persistent above-climatology deep
moisture, which could lead to flash flooding concerns especially
if storms develop over areas that saw excessive rainfall amounts
the previous day. A Marginal Risk remains a reasonable starting
point to cover this threat on Tuesday/Day 5. Meanwhile, the models
are starting to show more similar ideas for flow aloft to the
north, leading to a front stalling over the Plains (with moisture
increasing especially by Tuesday night) while awaiting upstream
troughing/surface waviness. This has led to an increasing signal
for locally heavy convective potential, currently with the best
focus over or near eastern Kansas into western/northern Missouri.
Thus the updated Day 5 ERO has introduced a Marginal Risk area over
this region. There continues to be potential for locally heavy
rainfall over other parts of the Plains/Mississippi Valley given
recent behavior of guidance. By midweek and beyond, additional
rounds of rain and thunderstorms are likely for the
central/southern Plains and Mid/Lower Mississippi Valley (perhaps
extending into nearby areas) as moisture surges ahead of a wavy
frontal system.
Elsewhere, one or more shortwaves/upper lows will lead to rounds
of precipitation across the northern tier. In the Northwest, some
higher elevation snow is possible with this activity, with the most
widespread coverage on Monday before snow levels may rise even
further. Mainly rain is expected farther east across the northern
Plains to Midwest/Great Lakes/Ohio Valley and into the
Northeast/Mid-Atlantic at times. Guidance is still in the process
of trending, but suggests the potential for a period of enhanced
northern Rockies/Plains precipitation that will be worth
monitoring. At the same time, these trends are indicating less
precipitation than previously forecast over the Pacific Northwest
by late in the week.
With the exception of the cooler West Coast and Northwest
especially Monday-Tuesday, the bulk of the lower 48 will have near
to warmer than average temperatures next week. An upper ridge over
the East Monday-Tuesday should help produce temperatures around
10-20F above normal, with temperatures in the 80s possibly as far
north as the Great Lakes region. Scattered daily record highs and
perhaps more numerous record warm lows are possible. Temperatures
are likely to gradually moderate but stay above average in the East
until late next week, depending on frontal progression. Meanwhile,
parts of the central U.S. will also see above normal temperatures
with anomalies around +10F Monday-Wednesday before cooling. The
Intermountain West to Rockies on the other hand should gradually
warm and see its greatest warm anomalies Thursday-Friday. However
note that recent guidance spread and variability yield lower than
average confidence in the temperature forecast over the West,
especially by the latter half of next week.
Rausch/Tate
Additional 3-7 Day Hazard information can be found on the WPC
medium range hazards outlook chart at:
https://www.wpc.ncep.noaa.gov/threats/threats.php
WPC medium range 500mb heights, surface systems, weather grids,
quantitative precipitation forecast (QPF), excessive rainfall
outlook (ERO), winter weather outlook (WWO) probabilities, heat
indices, and Key Messages can be accessed from:
https://www.wpc.ncep.noaa.gov/medr/5dayfcst500_wbg.gif
https://www.wpc.ncep.noaa.gov/medr/5dayfcst_wbg_conus.gif
https://www.wpc.ncep.noaa.gov/5km_grids/5km_gridsbody.html
https://www.wpc.ncep.noaa.gov/qpf/day4-7.shtml
https://www.wpc.ncep.noaa.gov/#page=ero
https://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4
https://www.wpc.ncep.noaa.gov/heat_index.shtml
https://www.wpc.ncep.noaa.gov/#page=ovw
Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
359 AM EDT Fri Apr 26 2024
Valid 00Z Sat Apr 27 2024 - 00Z Sat May 04 2024
Breezy trades may hold through Friday with upper/surface highs
centered northeast of Hawaii, but these features weakening will
cause winds to weaken as well by Saturday. Meanwhile to the
northwest of the state, upper/surface lows will track slowly
eastward into this weekend and early next week. In response to
these features, winds are likely to veer a bit and may become
east-southeast. Winds are forecast to stay at weak to moderate
levels and perhaps become a hybrid trade and land/sea breeze
pattern. Minor moisture plumes may also be drawn into the state at
times, with the first Friday night into Saturday increasing
showers particularly over windward areas of the Big Island
according to the HREF. Generally windward showers will be the main
chance for precipitation, since the upper ridge east of Hawaii is
likely to block the western lows/associated frontal system and any
heavier precipitation from reaching even the northwestern islands
through early next week. What is left of the weakening trough may
move across Hawaii around midweek or so. By the later part of next
week, surface high pressure is forecast to move north of the state
and promote strengthening easterly trades.
Tate
» Extreme Precipitation Monitor
+ Additional Links
- » Product Verification
- » Product Archive
- » Product Info
- » Additional formats of QPF: GRIB 2 | Shapefiles | KML
- » Other QPF Products
+ Forecast Discussion
Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
855 PM EDT Fri Apr 26 2024
Day 1
Valid 01Z Sat Apr 27 2024 - 12Z Sat Apr 27 2024
...A SLIGHT RISK OF EXCESSIVE RAINFALL EXISTS ACROSS PORTIONS OF
THE SOUTHERN PLAINS INTO THE LOWER TO MIDDLE MISSISSIPPI VALLEY
OVERNIGHT...
...01Z Excessive Rainfall Discussion...
The focus for additional heavy to potentially excessive rainfall
will continue to be across portions of the Southern Plains into the
Lower and Mid-Mississippi Valley...with a lesser probability of
excessive rainfall farther north. Highest rainfall rates and total
accumulation should continue to fall in the region of deepest
moisture and instability although placement of the cold pool
associated with earlier convection introduces some degree of
uncertainty with any additional convection later this evening and
through the overnight hours. At this point...CAMs are showing cells
becoming more progressive so trimmed some of the western boundary
of the Slight Risk and kept it ahead of QLCS moving into portions
of Arkansas and northeast Texas. Farther north...trimmed the
western boundary near the deep-layer upper cyclone where cooler and
drier air has begun to infiltrate.
Bann
...Summary...
Based on both current observational trends (radar/satellite/
mesoanalysis), along with the latest trends per the 12Z CAM
guidance, the Slight Risk area was expanded a bit farther southwest
to include more of east-central TX, including Fort Hood), while
also trimmed a bit across parts of southeast KS.
...Eastern Portions of the Plains into the Lower Missouri and Mid-
Upper Mississippi Valley...
Ongoing QLCS traversing MO and the MOKSAROK 4-state region is the
main driver for the more enhanced (high-end Slight Risk) across
these areas, though despite airmass destabilization farther west
across central KS, much (though not all) of the latest CAMs show
limited additional rainfall during the remainder of the D1 period
behind the QLCS given the shortwave DNVA.
With time today the better synoptic forcing lifts to the north,
resulting in a downward trend in forcing across the southern half
of the Slight risk, with weakening lower level convergence and also
less pronounced mid/upper level ascent. These larger scale factors
would generally favor weaker and less organized convection with
time today into tonight over these southern areas. Countering this
is a rather favorable thermodynamic environment, with plentiful
instability and moisture. Thus it seems most likely that if
convection this morning over OK and TX can grow upscale enough to
generate an organized outflow/cold pool, which the 12Z HRRR, ARWs,
and NAM CONUS-Nest show, then this mesoscale feature could be
enough to sustain an axis of more robust convection into the
afternoon. Any convection that is able to sustain and grow upscale
may exhibit some training and backbuilding characteristics into
the strong low level jet in place.
Farther north a Marginal risk is in place from northern MO into SD
and MN. Elevated showers and embedded thunderstorms will move
across this region this morning, but will be outrunning the better
instability...which should keep rainfall rates low enough to
prevent any more organized flood threat. As the surface low and
strong mid/upper forcing ejects into the Plains this afternoon
additional convective development is likely from eastern NE/SD into
portions of IA and MN. Some of this activity should be intense,
but generally should be moving at a quick enough pace to limit the
flash flood risk.
Hurley/Chenard
Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
855 PM EDT Fri Apr 26 2024
Day 2
Valid 12Z Sat Apr 27 2024 - 12Z Sun Apr 28 2024
...A MODERATE RISK OF EXCESSIVE RAINFALL EXISTS ACROSS PORTIONS OF
FAR NORTHERN TEXAS INTO EASTERN OKLAHOMA, SOUTHEAST KANSAS
SOUTHWEST MISSOURI, AND FAR NORTHWEST ARKANSAS...
...2000 UTC Update...
Per collaboration with WFOs SGF, ICT, and TSA, we have expanded
the Moderate Risk area slightly farther downstream (N-NE-E) across
those CWAs, based on (1) the recent heavy rainfall/increased RSM
per NASA SPoRT/lower FFGs per the RFC, and (2) the latest QPF
trends in the guidance. Within the Moderate Risk outlook area, the
ensemble PMM of 12Z models depicts a heavy QPF footprint of 3-6+
inches, with the 12Z HRRR, FV3, and both ARWs indicating embedded
7-9+ inch totals. The latest HREF and RRFS ensembles 50-70%
neighborhood probabilities of 12hr QPF exceeding 5" within the
Moderate Risk area between 00-12Z Sun. During the same time, both
ensembles show small areas of 15-25% probs of >8 inches across
northeast OK into southwest MO.
Hurley
...Previous Discussion...
A significant rainfall event still appears likely Saturday night
across portions of north central TX into central/eastern OK.
Overall not much has changed over the last couple model cycles, and
thus much of last nights discussion still holds true. Large scale
forcing really ramps up Saturday night with the approach of the mid
level trough and 250mb upper jet streak. With strong ridging to
the east, these features lift more northward than eastward during
the overnight hours, resulting in a prolonged period of impressive
upper level divergence centered over Oklahoma. The persistence of
this large scale forcing is typically indicative of a favorable
training convective setup.
In the lower levels we have a very strong 850mb jet in excess of
50 kts resulting in impressive moisture transport and convergence
near a slow moving cold front. This low level flow is nearly equal
and parallel to the deep layer mean flow, which typically supports
a backbuilding convective risk. The expectation is that with deep
layer mean flow nearly parallel to the low level boundary,
convective cells will tend to train and also backbuild into the
strong low level jet.
Convection should become intense and organized enough to develop
a stronger cold pool resulting in some eastward cell progression
with time. This eastward progression is the main wild card in
determining the magnitude of the flash flood risk with this event.
We do think there will be some eastward progression, but the
persistent forcing and strong low level jet both will be opposing a
significant eastward push...and thus tend to think we will see
enough persistence of convection to result in an organized flash
flood threat. Convection will be capable of 2-3"/hr rainfall, and
thus it will not take much persistence to start getting some
significant rainfall totals. While widespread 5"+ totals may not
occur, this event does appear to have the potential to produce a
swath(s) of as much as 4-8" of rainfall. This is expected to
result in an increasing, and locally significant, flash flood
threat Saturday night
Model guidance remains in decent agreement, all generally focusing
the highest swath of QPF from north central TX into
central/eastern OK. Although, as would be expected with any
convective forecast, there is still some uncertainty on where
exactly the highest QPF ends up, as the swath of the most excessive
amounts will likely be rather narrow. The GEM REG has been pretty
consistent with a swath heavy rainfall, and while the magnitudes
and areal extent are probably overdone in that model, do think it
represents a reasonable evolution of how things may play out
Saturday into Saturday night. The 00z ECMWF remains a bit further
southeast than the consensus. The 00z GFS has a secondary max over
eastern KS into western MO, and while heavy rain is expected here,
tend to think the GFS is overdoing this northern swath, and under
doing the swath over OK (this is a typical GFS bias). The
experimental machine learning GFS Graphcast actually appears to be
correcting this bias, and has an axis more similar to the GEM reg
(albeit lower magnitudes). The current placement of the MDT risk is
where the best overlap in ingredients and the model QPF consensus
resides, and was extended a bit more southwest into north central
TX with this update.
Across eastern KS into northwest MO and southern IA locally
excessive rainfall is also expected along an axis of stronger low
level convergence. But in general the thermodynamic ingredients
here are less favorable for a prolonged period of heavy rain
compared to the swath over OK, and thus a Slight risk should
suffice. A Marginal risk extends westward across NE into northeast
CO along/near the low track where convection near the warm front
may result in a localized flood risk.
Chenard
Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
855 PM EDT Fri Apr 26 2024
Day 3
Valid 12Z Sun Apr 28 2024 - 12Z Mon Apr 29 2024
...A SLIGHT RISK OF EXCESSIVE RAINFALL EXISTS ACROSS PORTIONS OF
THE SOUTHERN PLAINS INTO THE LOWER AND MIDDLE MISSISSIPPI VALLEY...
...2000 UTC Update...
Few changes made to the Day 3 ERO areas, though based on the latest
trends with the 12Z guidance, did nudge the eastern portion of the
Slight Risk area downshear a tad across the Mississippi and into
far southwest IL-western KY-western TN. Still too much spread in
the guidance at this point to support an upgrade to a Moderate
anywhere within the broad Slight Risk area, though based on the
latest model QPFs, at the very least a high-end Slight is still
anticipated with pockets of 3-5+ inches. Hopefully with newer
guidance (especially once getting into the CAM windows), we'll be
able to more confidently hone in on an area or areas for a
potential upgrade to a Moderate Risk, if necessary.
Hurley
...Previous Discussion...
Convection will likely be ongoing at 12z Sunday across portions of
OK and TX, a continuation of the Moderate risk day described above
for Saturday night. Current expectations are that convection will
have enough of a cold pool by this time to result in a decent
eastward propagation. Thus the flash flood risk should be
decreasing into Sunday morning, although some continued flash flood
risk is probable.
The bigger question becomes what happens on Sunday night. There is
some model disagreement on this, although the majority of solutions
would suggest an additional round of upscale convective development
is likely. This is also generally supported when looking at things
from an ingredients based perspective. With the main low lifting
off to the northeast over the Upper MS Valley, the portion of the
front over TX and AR should become nearly stationary. Meanwhile we
see a strong and persistent upper level divergence signature
centered near the TX/AR border, and a trailing mid level shortwave
ejecting into the southern Plains should only help to enhance lift
near the stalled low level convergence axis. Overall, ingredients
are similar to what we will see Saturday night over OK, thus
training and backbuilding convection appears probable.
Still think this event may very well eventually need a Moderate
risk given the setup and ingredients in place. However there
remains a bit of uncertainty with regards to where the best
convective training will be...with anywhere from northeast TX into
AR within the range of possibilities. Given this uncertainty, and
the fact that the overall synoptic setup, while similar to
Saturday night, is probably not quite as favorable (also noting
slightly lower model QPFs compared to day 2)...think sticking with
a higher end Slight risk is the best course of action for now.
Plus, rainfall Friday will likely play a role in if/where soil and
stream conditions will be more sensitive for flash flooding come
Sunday...so knowing how convection plays out Friday may help with
any eventual MDT risk placement Sunday. Thus the Slight risk
remains for now, and will continue to evaluate on future shifts.
A broad Marginal risk extends from MO northward into MN and WI,
generally along and east of the strong low and mid/upper forcing.
Convection here, while locally intense, should be quick moving,
limiting the extent of any flash flood risk. However this will be
the second strong low pressure and convective threat within a 3
day period...so can not rule out an eventual need for an embedded
Slight risk pending soil and stream response from round 1.
Chenard
NWS Weather Prediction Center College Park MD
301 PM EDT Fri Apr 26 2024
Ample moisture and instability will be present across much of the
central U.S. into Monday ahead of a Plains upper trough and
associated surface frontal system. The most likely focus for the
heaviest convection and rainfall is across the Lower Mississippi
Valley, where a Slight Risk is maintained in the Monday/Day 4
Excessive Rainfall Outlook. This may be a higher-end Slight Risk if
the heaviest model QPFs of 3-5 inches with rain rates over 2
inches per hour end up verifying. By Tuesday the upper-level
support will likely weaken, so overall expect lower rainfall
amounts and rain rates. However, some additional convection could
develop within an area of persistent above-climatology deep
moisture, which could lead to flash flooding concerns especially
if storms develop over areas that saw excessive rainfall amounts
the previous day. A Marginal Risk remains a reasonable starting
point to cover this threat on Tuesday/Day 5. Meanwhile, the models
are starting to show more similar ideas for flow aloft to the
north, leading to a front stalling over the Plains (with moisture
increasing especially by Tuesday night) while awaiting upstream
troughing/surface waviness. This has led to an increasing signal
for locally heavy convective potential, currently with the best
focus over or near eastern Kansas into western/northern Missouri.
Thus the updated Day 5 ERO has introduced a Marginal Risk area over
this region. There continues to be potential for locally heavy
rainfall over other parts of the Plains/Mississippi Valley given
recent behavior of guidance. By midweek and beyond, additional
rounds of rain and thunderstorms are likely for the
central/southern Plains and Mid/Lower Mississippi Valley (perhaps
extending into nearby areas) as moisture surges ahead of a wavy
frontal system.
Elsewhere, one or more shortwaves/upper lows will lead to rounds
of precipitation across the northern tier. In the Northwest, some
higher elevation snow is possible with this activity, with the most
widespread coverage on Monday before snow levels may rise even
further. Mainly rain is expected farther east across the northern
Plains to Midwest/Great Lakes/Ohio Valley and into the
Northeast/Mid-Atlantic at times. Guidance is still in the process
of trending, but suggests the potential for a period of enhanced
northern Rockies/Plains precipitation that will be worth
monitoring. At the same time, these trends are indicating less
precipitation than previously forecast over the Pacific Northwest
by late in the week.
With the exception of the cooler West Coast and Northwest
especially Monday-Tuesday, the bulk of the lower 48 will have near
to warmer than average temperatures next week. An upper ridge over
the East Monday-Tuesday should help produce temperatures around
10-20F above normal, with temperatures in the 80s possibly as far
north as the Great Lakes region. Scattered daily record highs and
perhaps more numerous record warm lows are possible. Temperatures
are likely to gradually moderate but stay above average in the East
until late next week, depending on frontal progression. Meanwhile,
parts of the central U.S. will also see above normal temperatures
with anomalies around +10F Monday-Wednesday before cooling. The
Intermountain West to Rockies on the other hand should gradually
warm and see its greatest warm anomalies Thursday-Friday. However
note that recent guidance spread and variability yield lower than
average confidence in the temperature forecast over the West,
especially by the latter half of next week.
Rausch/Tate
NWS Weather Prediction Center College Park MD
301 PM EDT Fri Apr 26 2024
Ample moisture and instability will be present across much of the
central U.S. into Monday ahead of a Plains upper trough and
associated surface frontal system. The most likely focus for the
heaviest convection and rainfall is across the Lower Mississippi
Valley, where a Slight Risk is maintained in the Monday/Day 4
Excessive Rainfall Outlook. This may be a higher-end Slight Risk if
the heaviest model QPFs of 3-5 inches with rain rates over 2
inches per hour end up verifying. By Tuesday the upper-level
support will likely weaken, so overall expect lower rainfall
amounts and rain rates. However, some additional convection could
develop within an area of persistent above-climatology deep
moisture, which could lead to flash flooding concerns especially
if storms develop over areas that saw excessive rainfall amounts
the previous day. A Marginal Risk remains a reasonable starting
point to cover this threat on Tuesday/Day 5. Meanwhile, the models
are starting to show more similar ideas for flow aloft to the
north, leading to a front stalling over the Plains (with moisture
increasing especially by Tuesday night) while awaiting upstream
troughing/surface waviness. This has led to an increasing signal
for locally heavy convective potential, currently with the best
focus over or near eastern Kansas into western/northern Missouri.
Thus the updated Day 5 ERO has introduced a Marginal Risk area over
this region. There continues to be potential for locally heavy
rainfall over other parts of the Plains/Mississippi Valley given
recent behavior of guidance. By midweek and beyond, additional
rounds of rain and thunderstorms are likely for the
central/southern Plains and Mid/Lower Mississippi Valley (perhaps
extending into nearby areas) as moisture surges ahead of a wavy
frontal system.
Elsewhere, one or more shortwaves/upper lows will lead to rounds
of precipitation across the northern tier. In the Northwest, some
higher elevation snow is possible with this activity, with the most
widespread coverage on Monday before snow levels may rise even
further. Mainly rain is expected farther east across the northern
Plains to Midwest/Great Lakes/Ohio Valley and into the
Northeast/Mid-Atlantic at times. Guidance is still in the process
of trending, but suggests the potential for a period of enhanced
northern Rockies/Plains precipitation that will be worth
monitoring. At the same time, these trends are indicating less
precipitation than previously forecast over the Pacific Northwest
by late in the week.
With the exception of the cooler West Coast and Northwest
especially Monday-Tuesday, the bulk of the lower 48 will have near
to warmer than average temperatures next week. An upper ridge over
the East Monday-Tuesday should help produce temperatures around
10-20F above normal, with temperatures in the 80s possibly as far
north as the Great Lakes region. Scattered daily record highs and
perhaps more numerous record warm lows are possible. Temperatures
are likely to gradually moderate but stay above average in the East
until late next week, depending on frontal progression. Meanwhile,
parts of the central U.S. will also see above normal temperatures
with anomalies around +10F Monday-Wednesday before cooling. The
Intermountain West to Rockies on the other hand should gradually
warm and see its greatest warm anomalies Thursday-Friday. However
note that recent guidance spread and variability yield lower than
average confidence in the temperature forecast over the West,
especially by the latter half of next week.
Rausch/Tate
» Interactive Winter Weather Map (Day 4-7)
» Winter Storm Severity Index
+ Forecast Discussion (Day 1-3)
Probabilistic Heavy Snow and Icing Discussion
NWS Weather Prediction Center College Park MD
315 PM EDT Fri Apr 26 2024
Valid 00Z Sat Apr 27 2024 - 00Z Tue Apr 30 2024
...Great Basin into the Rockies...
Days 1-2...
A mid-level shortwave and upper jet will continue to carve out an
anomalously deep trough over the Southwest, with a closed low
developing over the Four Corners tomorrow. This will bring
widespread high-elevation snow from the Sierra to the Rockies, with
locally heavy accumulations expected.
Areas more likely to be impacted by heavy accumulations include the
western Wyoming ranges. Easterly winds sandwiched between a
mid-level
low moving through Utah and high pressure over Montana will
combine with favorable upper forcing to support heavy snow this
evening into the overnight, especially along the Wind River Range
(above 9000 ft). WPC PWPF shows 50 percent or greater probabilities
for accumulations of a foot or more along the favored terrain.
The central Rockies, from the Medicine Bow Mountains south along
the Front Range, will likely be impacted as well. As a mid-level
center develops over eastern Colorado, upslope flow along with
left-exit region upper jet forcing will support heavy snow across
the region beginning overnight and continuing into late Saturday.
For areas above 8000 ft, probabilities for accumulations of a foot
or more are above 50 percent.
...Pacific Northwest...
Day 3...
While unsettled weather is expected across the region through the
period, an upper-level shortwave associated with a low sliding
southeast from the Gulf of Alaska and the northeastern Pacific will
move across the region on Monday, driving snow levels down and
increasing the coverage of accumulating snows across the Olympics
and Cascades. This includes the Cascades passes, where WPC PWPF
indicates that at least a few inches of snow can be expected on
Monday.
The probability of significant icing is less than 10 percent.
Pereira
- » Experimental Winter Storm Outlook
- » Probabilistic Winter Storm Severity Index
- » Product Verification
- » Product Archive
- » Product Info
- » Forecast Surface Low Positions: Uncertainty Circles | Ensemble Clusters
- » Other Winter Weather Products
NWS Weather Prediction Center College Park MD
301 PM EDT Fri Apr 26 2024
Valid 12Z Mon Apr 29 2024 - 12Z Fri May 03 2024
...Potentially severe thunderstorms and heavy rain causing flash
flooding are forecast to continue in the Lower Mississippi Valley
Monday...
...Overview...
Upper troughing will support a surface frontal system with
widespread thunderstorms ahead of it across the central U.S. into
Monday. Heavy rain is likely to cause flash flooding in the Lower
Mississippi Valley in particular, while severe weather may also be
a threat. The upper pattern looks to become more zonal after the
early part of the week, with increasing uncertainty in
shortwave/embedded upper low details and surface specifics from the
Pacific eastward. For the Lower 48 there is at least a general
theme of a leading system followed by another frontal system
affecting the central-eastern U.S. by the latter half of the week,
with both serving to focus areas of showers and thunderstorms.
There is still a lot of uncertainty over the Northwest by late next
week though. Near to above normal temperatures should prevail over
much of the East into at least the southern half of the Plains
through Intermountain West, while the Northwest and possibly other
northern tier areas may see one or more days of below normal highs.
...Guidance/Predictability Assessment...
Recent variability/trending and spread in the guidance leads to
below average confidence in some important aspects of the forecast
next week. Through the 00Z/06Z cycles, there were essentially two
primary layers of uncertainty. The first involves the trough/upper
low(s) over the Northwest U.S. and British Columbia as of early
Monday. Over the past day or so the GFS/ECMWF and their ensemble
means have trended toward greater progression of this feature whose
energy could ultimately split into two pronounced upper troughs
and/or lows. In contrast, the 00Z UKMET/CMC-CMCens clustered with
what had been the prior consensus of holding the initial feature
back near the Pacific coast while awaiting input from upstream
Pacific energy. 00Z ECMWF-initialized machine learning models (MLs)
agreed upon the more progressive theme, thus recommending
exclusion of the 00Z UKMET/CMC from the forecast. However the MLs
suggested that the upper energy could be more consolidated into one
upper low (located near the northern High Plains as of early
Wednesday) versus what the GFS/ECMWF were showing.
Beyond this discrepancy, guidance diverged even more with respect
to Pacific/western U.S. flow later in the week. ECMWF runs and the
00Z GFS along with the GEFS/ECens means brought a trough/possible
compact upper low into the Northwest (with a lot of spread among
individual ensemble members), but a slight majority of the MLs
actually built a ridge over the West Coast by late week due to
greater troughing over the Pacific near 140-150W. The 06Z GFS
trended that way too, deflecting the late week upper low farther
north into Canada.
In light of guidance differences, ML suggestions, and continuity,
the updated forecast used a blend of 00Z and 12Z/25 ECMWF runs and
the 00Z/06Z GFS early in the period followed by a 40-50 percent
weight of the 06Z GEFS/00Z ECens means with lingering weight of
those GFS/ECMWF runs mid-late period. This solution yielded only
minor nudges from continuity in this lower predictability regime.
In the new 12Z guidance, the UKMET/CMC have trended significantly
toward other dynamical guidance for progression of the initial
Northwest U.S./British Columbia feature. This still leaves a
difference between the dynamical solutions and more consolidated
MLs. The CMC/UKMET also favor higher heights along the West Coast
by late week while the GEFS mean still brings in a modest trough.
...Weather/Hazards Highlights...
Ample moisture and instability will be present across much of the
central U.S. into Monday ahead of a Plains upper trough and
associated surface frontal system. The most likely focus for the
heaviest convection and rainfall is across the Lower Mississippi
Valley, where a Slight Risk is maintained in the Monday/Day 4
Excessive Rainfall Outlook. This may be a higher-end Slight Risk if
the heaviest model QPFs of 3-5 inches with rain rates over 2
inches per hour end up verifying. By Tuesday the upper-level
support will likely weaken, so overall expect lower rainfall
amounts and rain rates. However, some additional convection could
develop within an area of persistent above-climatology deep
moisture, which could lead to flash flooding concerns especially
if storms develop over areas that saw excessive rainfall amounts
the previous day. A Marginal Risk remains a reasonable starting
point to cover this threat on Tuesday/Day 5. Meanwhile, the models
are starting to show more similar ideas for flow aloft to the
north, leading to a front stalling over the Plains (with moisture
increasing especially by Tuesday night) while awaiting upstream
troughing/surface waviness. This has led to an increasing signal
for locally heavy convective potential, currently with the best
focus over or near eastern Kansas into western/northern Missouri.
Thus the updated Day 5 ERO has introduced a Marginal Risk area over
this region. There continues to be potential for locally heavy
rainfall over other parts of the Plains/Mississippi Valley given
recent behavior of guidance. By midweek and beyond, additional
rounds of rain and thunderstorms are likely for the
central/southern Plains and Mid/Lower Mississippi Valley (perhaps
extending into nearby areas) as moisture surges ahead of a wavy
frontal system.
Elsewhere, one or more shortwaves/upper lows will lead to rounds
of precipitation across the northern tier. In the Northwest, some
higher elevation snow is possible with this activity, with the most
widespread coverage on Monday before snow levels may rise even
further. Mainly rain is expected farther east across the northern
Plains to Midwest/Great Lakes/Ohio Valley and into the
Northeast/Mid-Atlantic at times. Guidance is still in the process
of trending, but suggests the potential for a period of enhanced
northern Rockies/Plains precipitation that will be worth
monitoring. At the same time, these trends are indicating less
precipitation than previously forecast over the Pacific Northwest
by late in the week.
With the exception of the cooler West Coast and Northwest
especially Monday-Tuesday, the bulk of the lower 48 will have near
to warmer than average temperatures next week. An upper ridge over
the East Monday-Tuesday should help produce temperatures around
10-20F above normal, with temperatures in the 80s possibly as far
north as the Great Lakes region. Scattered daily record highs and
perhaps more numerous record warm lows are possible. Temperatures
are likely to gradually moderate but stay above average in the East
until late next week, depending on frontal progression. Meanwhile,
parts of the central U.S. will also see above normal temperatures
with anomalies around +10F Monday-Wednesday before cooling. The
Intermountain West to Rockies on the other hand should gradually
warm and see its greatest warm anomalies Thursday-Friday. However
note that recent guidance spread and variability yield lower than
average confidence in the temperature forecast over the West,
especially by the latter half of next week.
Rausch/Tate
Additional 3-7 Day Hazard information can be found on the WPC
medium range hazards outlook chart at:
https://www.wpc.ncep.noaa.gov/threats/threats.php
WPC medium range 500mb heights, surface systems, weather grids,
quantitative precipitation forecast (QPF), excessive rainfall
outlook (ERO), winter weather outlook (WWO) probabilities, heat
indices, and Key Messages can be accessed from:
https://www.wpc.ncep.noaa.gov/medr/5dayfcst500_wbg.gif
https://www.wpc.ncep.noaa.gov/medr/5dayfcst_wbg_conus.gif
https://www.wpc.ncep.noaa.gov/5km_grids/5km_gridsbody.html
https://www.wpc.ncep.noaa.gov/qpf/day4-7.shtml
https://www.wpc.ncep.noaa.gov/#page=ero
https://www.wpc.ncep.noaa.gov/wwd/pwpf_d47/pwpf_medr.php?day=4
https://www.wpc.ncep.noaa.gov/heat_index.shtml
https://www.wpc.ncep.noaa.gov/#page=ovw
Displays flood and flash flood reports as well as intense rainfall observations for user-selectable time ranges and customizable geographic regions. Includes ability to download reports and associated metadata in csv format.
Plots of GEFS probabilistic forecast of precipitation, temperature, and sea-level pressure exceeding various thresholds.
Custom plots of Local Storm Reports across the Contiguous United States. Reports include rain, snow, ice, and severe weather, as well as other significant information from storm spotters.
Displays the climatological significance of precipitation forecast by WPC. The climatological significance is represented by Average Recurrence Intervals (ARIs) of precipitation estimates from NOAA Atlas-14 and Atlas2.
An interactive situational awareness table that displays anomalies, percentiles, and return intervals from the GEFS, NAEFS, and ECMWF Ensembles (login required to view ECMWF data).
*Please note that there is currently an issue where only users on a NOAA network can access this page. We are actively working to resolve this problem.
Interactive display of where temperatures could approach or exceed records within the contiguous U.S. (based on NDFD temperature forecasts)
Displays Days 1-7 NDFD maximum and minimum temperatures, along with their respective departures from climatology.
An interactive tool that depicts areas of heavy snowfall from individual members of high-resolution short range ensemble forecasts.
Displays forecast information and its climatological context to quickly alert a forecaster when a record or neear-record breaking event is possible. This tool is available for both CONUS and Alaska.
Interface for specialized WPC Excessive Rainfall Outlook Maps for NWS County Warning Areas and States.
Analog guidance that uses an objective approach to find historical events that are similar to the upcoming forecast.
Nationally consistent and skillful suite of calibrated forecast guidance based on a blend of both NWS and non-NWS numerical weather prediction model data and post-processed model guidance.
A portal for atmospheric river forecasts and diagnostics from the Center for Western Weather and Water Extremes.
An interactive display of time series plots from GEFS ensemble members at a point.
A variety of useful tools generated at The Storm Prediction Center (SPC).
Output from the ECMWF 'Ensemble Prediction System' (ENS) for four parameters: mean sea level pressure, 850 hPa temperature, 850 hPa wind speed, and 500 hPa geopotential height.