Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
320 AM EDT Fri May 15 2026

Valid 12Z Mon May 18 2026 - 12Z Fri May 22 2026


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

...General Overview...

An amplified upper level pattern will be in place for the beginning
of next week, with an anomalous ridge over the east-central U.S.
supporting an early season heat wave, and a strong trough over the
Rockies that will bring a round of late season snow for the higher
elevations of Colorado and Wyoming. At the interface of these two
features will be a strong cold front that will be crossing the
Plains and Midwest with multiple rounds of heavy rainfall and
strong/severe thunderstorms.

...Guidance/Predictability Assessment...

The deterministic model guidance suite features good overall
agreement for the beginning of the period Monday, and a general
model compromise works as a starting point for fronts and
pressures. Looking ahead to mid-week, recent runs of the CMC have
been slower with ejecting the western U.S. trough, and maintain the
eastern U.S. ridge and heatwave longer than the other guidance. The
GFS has trended less strong with a shortwave crossing the Midwest
and Ohio Valley by Friday when compared to its 18Z run. The
ensemble means were increased to about half by Friday as
deterministic model spread increases.

...Weather/Hazards Highlights...

A dynamic storm system crossing the northern Plains to the Upper
Midwest will bring widespread showers and thunderstorms from Texas
to Minnesota ahead of a strong cold front. The best combination of
instability and dynamics aloft is expected over Iowa and portions
of adjacent states on Monday, and thus where the best lift in the
atmosphere will be for heavy rainfall. Given the potential for
training thunderstorms with high rainfall rates, a Slight Risk of
excessive rainfall will be valid for the Day 4/Monday time period
for this region. There is also a good chance for severe
thunderstorms to develop in the warm sector ahead of the front, and
this is something that the Storm Prediction Center is actively
monitoring in the days ahead.

Going into Day 5/Tuesday, the best focus for heavy rainfall is
expected to be across Texas and extending eastward to Arkansas and
the Mid-South as the front drops farther to the south, and
intercepts a very humid and unstable airmass. For now, a broad
Marginal Risk area is valid for this time, but future upgrades to a
Slight Risk are likely as the event gets closer in time with
better confidence on the QPF axis placement. Additional heavy
rainfall is likely going into Wednesday as well for these same
general areas.

In the temperature department, heat will be making headlines for
much of the Eastern U.S. for the first half of the week, with the
hottest conditions across interior portions of the Mid-Atlantic
into the Carolinas where highs are likely to reach the lower to
middle 90s. This will likely be warm enough to establish some daily
record highs before a cold front brings relief from the Ohio Valley
to the Mid-Atlantic/Northeast by Thursday. The opposite will hold
true for the Intermountain West and Rockies with below normal
readings to start the week, and snow for the higher elevations.

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