355
FXUS02 KWBC 110704
PMDEPD

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
304 AM EDT Tue Mar 11 2025

Valid 12Z Fri Mar 14 2025 - 12Z Tue Mar 18 2025


...Heavy rain/flooding and severe weather possible for the
Mississippi/Ohio/Tennessee Valleys and Southeast late week...

...Widespread high winds cause fire danger in the southern Plains
and localized blizzard conditions in the north-central CONUS...

...Multiple rounds of precipitation likely in the West...


...Overview...

The first weather feature of concern late this week will be an
upper trough with embedded upper low supporting a strengthening
surface low in the central High Plains as the period begins Friday.
This low will track northeastward into the Upper Midwest into
Saturday with potent cold fronts to its south. Hazards associated
with the surface low pressure system will include heavy rain and
severe thunderstorms in the Mississippi Valley beginning Friday and
into the Southeast and Tennessee/Lower Ohio Valleys Saturday.
Convection should reach the Eastern Seaboard Sunday. Snow is
possible on the backside of the low in the northern half of the
Plains into the Upper Midwest Friday-Saturday. Meanwhile areas of
strong winds are likely, which could cause fire danger especially
in the southern Plains. Warmer than normal temperatures will be
common ahead of the low and its cold fronts, with cooler
temperatures behind. Behind that low, another upper trough is
forecast to approach the West this weekend and spread additional
precipitation there, lasting into early next week.


...Guidance/Predictability Assessment...

Model guidance continues to show reasonably good agreement for the
larger scale features through the medium range. The upper trough
and embedded upper low over the central U.S. will allow for a
strong surface low to consolidate in the central High Plains. The
surface low looks to be around 980mb early Friday and in the 970s
early Saturday in the Upper Midwest, per the average of models and
ensemble members. On smaller scales, models vary a bit more with
forecast aspects like the positioning of backdoor fronts in the
East late this week. AI/ML models have tended to show the front
farther south for cooler Mid-Atlantic temperatures than the
deterministic guidance. Another area of minor uncertainty is with
possible secondary lows developing in the Great Lakes region behind
the main low track. But overall, a deterministic model blend
favoring the ECMWF and GFS worked well for the early part of the
forecast period.

Model spread is a little greater with the next upper trough
approaching that should be located over the eastern Pacific early
next week. Models have varied on the depth of a surface low near
Vancouver Island or the Pacific Northwest over the past couple of
days, but recent 00Z guidance is more agreeable for a relatively
deep low. While models generally agree in the broad upper trough
axis pivoting south and east early next week, some models also show
some energy ejecting east as a northern tier shortwave. The 12Z
ECMWF was particularly aggressive with the shortwave suppressing
the northern side of the upper ridge in between the two main
troughs, and produced a surface low near the North Dakota/Canada
border by early Monday. Leaned away from this as other models,
including the the EC-based AI/ML models, were not on board.
However, the incoming 00Z model suite does show some hints of a
shortwave and surface low. Yet another surface low, though likely
much weaker, could develop in the High Plains early next week ahead
of the second West trough. Given the increasing model spread, the
WPC forecast increased the proportion of ensemble means in the
blend to half Day 6 and a bit more Day 7 to reduce individual model
differences.


...Weather/Hazards Highlights...

As the primary upper trough moves into the central U.S., there is
high confidence in surface low development/consolidation in the
central Plains by Friday with strong fronts and northeastward
progression of the system thereafter. Potential exists for this low
to challenge some sea level pressure records for March from
eastern Nebraska into parts of Minnesota/Wisconsin. On the backside
of the low, snow may be possible across the central High Plains
and into the Dakotas on Friday and Friday night. There is higher
confidence for meaningful snow across the eastern Dakotas into
western Minnesota by Saturday wrapping around the low. Some of
these areas may initially see rain in the warm sector, and a
transition zone of ice is also possible. Widespread high winds in
the central U.S. are another potential hazard with the low. In
northern areas, locations that receive snow could also receive
blizzard conditions Friday-Saturday given the strong winds.
Meanwhile farther south, high winds in the southern Rockies and
southern Plains will cause fire weather concerns.

Rain and thunderstorm chances will emerge ahead of the cold front
across the Mississippi Valley on Friday. The Storm Prediction
Center is highlighting severe potential there. Most guidance (aside
from GFS runs) shows heavy rain rates beginning late Friday into
Friday night that could cause flooding concerns. The Day 4/Friday
ERO maintains a Marginal Risk for the Lower/Middle Mississippi
Valley and Mid-South on Friday. By Saturday, rain totals are
forecast to become even heavier as the larger system slows and some
training of high rain rates is possible in an unstable environment
with good dynamics for lift. The first take at the Day 5/Saturday
ERO shows a Slight Risk of flash flooding across much of Alabama
and Tennessee and nearby, while a surrounding Marginal Risk reaches
from the central Gulf Coast into the Ohio Valley. SPC also
indicates severe potential for similar areas Saturday. Rain and
thunderstorms area likely to push across the East on Sunday ahead
of the cold front continuing eastward.

Additional rounds of precipitation are likely in the West late
this week into the weekend with multiple frontal systems channeling
Pacific moisture inland. Rain amounts in the Pacific Northwest to
northern California look to stay below thresholds for any excessive
rainfall risk through Friday, but chances for heavy precipitation
(lower elevation rain and higher elevation snow) could increase by
the weekend for the Pacific Northwest into California. Current
forecasts show a weak to moderate atmospheric river coming into the
Pacific Northwest Saturday night and moving southward into
California on Sunday. Held off from delineating any area in the Day
5/Saturday ERO as the coastal Pacific Northwest is not very
sensitive to heavy rain, but some localized rain rates of an inch
per hour or more are possible, which could make the flooding risk
nonzero. The AR currently looks to weaken as it pushes into central
and southern California Sunday, hopefully precluding too many
flooding issues over recent burn scars. Precipitation is also
likely farther east into the Interior West and Rockies through this
weekend and early next week.

Above average temperatures are likely over the eastern half of the
country Friday. Temperature anomalies of 20 to as much as 35
degrees above normal are forecast Friday for the Upper Midwest as
highs reach the 60s and 70s. Farther south, temperatures in Texas
into the Lower Mississippi Valley could reach the 80s while
localized areas like far South Texas can expect 90s, even
approaching 100F. Warmer than normal temperatures will gradually
shrink in area into the weekend as possibly multiple cold fronts
track east. Temperatures of 20 to 30 degrees above average will be
more limited to the Great Lakes on Saturday, and warmer than normal
temperatures by 15-25F are likely in the Northeast over the
weekend. There could be a few daily record highs isolated across
the central to eastern U.S., but there could be more widespread
record warm lows from the Midwest through the East Friday-Sunday if
the morning mins hold for the calendar day. After near normal
temperatures return, temperatures may warm to above average again
in the central and eastern U.S. early next week with another bout
of upper ridging. Meanwhile in the West, the initial upper
troughing will promote below normal temperatures across the region
Friday into Saturday. Highs are forecast to be generally below
average by 15-20 degrees for the central Great Basin and Southwest,
while lows of 5-15 degrees below normal are likely. Temperatures
should moderate somewhat by Sunday as the trough pulls away, but
another trough approaching could lead to another round of cool
temperatures there early next week.


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




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