821
FXUS02 KWBC 171912
PMDEPD

Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
312 PM EDT Sun May 17 2026

Valid 12Z Wed May 20 2026 - 12Z Sun May 24 2026


***Multiple rounds of heavy rain and severe storms expected for the
 southern Plains, and early season heatwave ends for the East
 Coast states***

...General Overview...

A moderately amplified upper level pattern over the country during
the middle of the week is expected to become more quasi-zonal by
next weekend, as the trough lifts out from the Rockies and the
northern Plains, and the eastern U.S. ridge gets flattened with a
return to more typical temperatures for the month of May, with
relief from the early season heat wave. A stalling frontal boundary
with shortwave impulses aloft will fuel the development of multiple
thunderstorm complexes from Texas to the Deep South, with episodes
of heavy rainfall and strong/severe storms. Mainly dry conditions
are expected for most of the western U.S.


...Guidance/Predictability Assessment...

Models are in reasonably good agreement on the overall synoptic
pattern evolution across the lower 48 during the medium range
period. There`s some uncertainty regarding the existence and
timing of small shortwave purtubations rotating through the
Southern Plains and Lower Mississippi Valley beginning mid-week.
This translates to QPF uncertainty over these same areas since the
mode of precip will likely be convective in nature. The GFS is also
notably more progressive than the other models when it comes to the
propagation of a closed mid-level low through the North-Central
U.S. this week.

A general model blend consisting of the available deterministic and
Euro Ai guidance was used through day 4. The UKMET and Canadian
models were removed from the blend on day 5 for diverging from
consensus. The ensemble means are introduced to the blend on day 5
and gradually increased in weighting preference through day 7.


...Weather/Hazards Highlights...

Heavy rainfall is expected to make weather headlines going into the
latter half of the work week from western Texas to the Tennessee
River Valley. The highest QPF should be across central Texas where
multiple mesoscale convective systems will develop and affect the
same areas on multiple days. For the Day 4/Wednesday-Wednesday
night time period, a Slight Risk will be valid from near Del Rio to
Longview, Texas where 1-3 inches of rainfall is likely with storms
producing high rainfall rates. This lingers going into Thursday as
well with a broad Marginal Risk extending from the Rio Grande to
Mississippi, with possible upgrades to Slight Risk in future
outlooks as timing and placement become clearer. Lighter
precipitation is expected farther to the east across the Carolinas
into Virginia with the cold front dropping south, and also for
portions of the Ohio Valley. Valley showers and mountain snow are
likely for portions of Montana and Wyoming on Wednesday before a
drier weather pattern ensues by the end of the week.

In terms of temperatures, expect another day of hot weather across
the East Coast region on Wednesday with highs reaching the lower to
middle 90s from the Carolinas to southern New England, with the
hottest readings likely to be over Virginia. Some daily record
highs are likely given the potential for some 20 degree above
average anomalies. A welcomed relief is expected to arrive on
Thursday as a strong cold front reaches the Mid-Atlantic by this
time, and probably lasting into Friday and Saturday as well. A cold
air damming type event may become established east of the
Appalachians with overcast skies and periods of mainly light rain
at times. The front likely stalls over the Southeast with warm and
humid conditions continuing south of the boundary. Elsewhere,
relatively cool conditions across the central/northern Plains are
expected to gradually warm through the forecast period.


Kebede/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, excessive rainfall outlook, winter weather outlook probabilities, heat indices and Key Messages are at:

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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