308
FXUS02 KWBC 120658
PMDEPD

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
258 AM EDT Mon May 12 2025

Valid 12Z Thu May 15 2025 - 12Z Mon May 19 2025

...Heavy rain for the Northern Plains and heat builds across Texas...


...General Overview...

The slow moving upper low across the Southeast U.S. through the
middle of this week will be weakening and evolving into an open
trough by Thursday as it exits the East Coast. Another upper trough
and closed low across the Northern Rockies mid-week will sustain a
surface low crossing the Northern Plains and then into south-
central Canada by the end of the week, with heavy rain for the
Dakotas/Minnesota and late season mountain snow for the northern
Rockies. A second trough will likely develop across the interior
West by next weekend with an upper ridge redeveloping across the
Plains. Widespread above normal temperatures are likely east of the
Rockies through much of the forecast period.

...Guidance/Predictability Assessment...

The 00Z model guidance suite features very good synoptic scale
agreement for the middle to end of the week, with a multi-
deterministic model blend sufficing as a starting point in the
forecast process. The GFS is a little to the north of the model
consensus by early Saturday with the low pressure system near the
northern Great Lakes, whereas the ECMWF is a little to the south
and the AIFS falling near the middle of the guidance. For the next
trough building out West, the guidance has trended a little more
amplified with the CMC/GFS depicting a closed low developing over
the Great Basin by next Monday. The ensemble means were increased
to about half by that time.

...Weather/Hazards Highlights...

The region with heaviest rainfall going into the second half of the
work week will be across North Dakota and into Minnesota. Although
rainfall rates are not expected to be all that high, multiple
hours of moderate rainfall with rates of half an inch per hour in
some cases may just be enough to cause some minor flooding issues
in vulnerable areas, and therefore the Marginal Risk area has been
maintained for Thursday (Day 4) from eastern North Dakota into
central/northern Minnesota. Going into Friday (Day 5), showers and
thunderstorms increase in coverage and intensity across the Mid-
South in the general vicinity of a quasi-stationary front that will
be intercepting advection of deep moisture from the south. A
Marginal Risk area is now valid from Arkansas to eastern Kentucky
where the model QPF is strongest for organized convection.

Elsewhere across the nation, the Storm Prediction Center is
monitoring the potential for some severe storms on Thursday across
portions of the Midwest. Out West, it will seem more like March across
the northern Rockies with heavy snow for the highest ranges of
southwestern Montana and northern Wyoming, with the potential for
6-12 inches of accumulation in some cases through mid-week, and a
second round of snow for the central and northern Rockies Sunday
into Monday as the next upper trough and shortwave moves into the
region. Lighter snows are likely elsewhere across the higher
terrain of the northern Rockies and Intermountain West.

Very warm weather will be commonplace across the eastern half of
the country to close out the work week, with highs well into the
80s and even lower 90s from the Ohio Valley and Mid-Atlantic
southward to the Gulf Coast. Very hot conditions are expected
across southern Texas for the entire forecast period with highs
exceeding 100 degrees near the Rio Grande, and HeatRisk reaching
the major to extreme category for some of these areas. In
contrast, chilly conditions are likely for the Intermountain West
and Northern Rockies with highs running 5-15 degrees below average
with the upper level trough and increased cloud cover.

Hamrick

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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