139
FXUS02 KWBC 130658
PMDEPD

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
258 AM EDT Tue May 13 2025

Valid 12Z Fri May 16 2025 - 12Z Tue May 20 2025

***Heat builds across the southern Plains while late season snow is
 expected for the Rockies***


...General Overview...

The strong low pressure system over the northern Plains on Thursday
is forecast to lift northeast across Ontario going into Friday,
with a strong trailing cold front that will bring a refreshing
change to cooler temperatures. Numerous showers and storms are
likely ahead of the front from the Mid-South to the Ohio Valley and
Great Lakes. Attention then turns to the Intermountain West by the
weekend as another amplified upper trough and closed low develops
and brings additional rounds of valley rain and mountain snow
along with cold conditions for this time of year. Heat will
continue to make weather headlines for the south-central U.S. with
lots of sunshine and an upper ridge axis governing the overall
weather pattern.

...Guidance/Predictability Assessment...

The 00Z model guidance suite features very good synoptic scale
agreement for the end of the week, with a multi-deterministic
model blend sufficing as a starting point in the forecast process
and slightly more weighting applied to the ECMWF/GFS solutions.
The UKMET is a bit to the northwest of the model consensus with
the storm system over the northern Great Lakes, and the CMC is
stronger with the upper ridge axis near the Southeast U.S. coast
over the weekend. The guidance agrees well with the next amplifying
trough across the interior West by Sunday, but there are some
differences in the evolution of the downstream surface low over the
central Plains by next Tuesday. The ensemble means were increased
to about 40% that time.

...Weather/Hazards Highlights...

Showers and thunderstorms increase in coverage and intensity
across the Mid-South and Ohio Valley ahead of a cold front that
will be intercepting deeper return moisture. An ERO Marginal Risk
area remains valid for Friday (Day 4) from Arkansas to the central
Appalachians, with an expansion northward to include southern
portions of Illinois, Indiana, and Ohio where the 00Z guidance has
trended heavier with expected rainfall. Going into Saturday (Day 5)
attention then turns to portions of the southern Plains and
extending to the Mid-South with enhanced moisture convergence near
the same frontal boundary and ahead of a developing wave of low
pressure near the Texas Panhandle.

Elsewhere across the nation, the Storm Prediction Center is
monitoring the potential for severe weather from the Midwest to the
Mid-South to close out the work week with favorable instability and
kinematics. Across the Rockies, expect additional chances for late
season snow for the central and northern Rockies by Sunday into Monday
as the next upper trough and shortwave moves in, with the potential
for over a foot of accumulation for some of the highest mountain
ranges. Numerous showers are also likely to develop across the
Great Basin over the weekend in response to the developing upper
low, and this may become locally heavy enough to eventually need a
Marginal Risk area for excessive rainfall as the event gets closer.

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 some lower-middle 90s from the Ohio Valley and Mid-
Atlantic southward to the Gulf Coast. Very hot conditions are
expected across southern Texas through the upcoming weekend with
highs exceeding 100 degrees near the Rio Grande and into much of
central Texas, 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/Plains with highs
running 10 to perhaps 20 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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