Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
400 AM EDT Tue May 21 2024

Valid 12Z Tue May 21 2024 - 12Z Thu May 23 2024

...An increasing threat of severe weather and excessive rainfall as well
as high winds expected to overspread the northern Plains and upper Midwest
today through tonight and into Wednesday morning...

...Severe weather and heavy rain threat will emerge across the southern
Plains to the mid-Mississippi Valley on Wednesday...

...Cool conditions with periods of shower and high elevation snow chances
from the Rockies to the Pacific Northwest...

...Well above average temperatures across the central Plains will be
replaced by cooler conditions but summer-like weather expected to continue
across the southern Plains to the Northeast...

A persistent weather pattern will continue to send energetic and
fast-moving weather systems onshore from the Pacific Ocean into the
Northwest through the short-range forecast period.  These systems will
tend to intensify as they reach into the mid-section of the country.  One
such system is developing and tracking toward the northeast across the
central Plains this morning.  The threat of severe weather and heavy rain
will be expanding toward the upper Midwest by tonight along with
increasingly windy conditions when the low pressure system is forecast to
become quite deep and intense.  Thunderstorms that erupt ahead of a potent
cold front may contain damaging wind gusts, large hail, and a few
tornadoes, from the central Plains to the Great Lakes, and especially over
Iowa, where the Storm Prediction Center has issued a Moderate Risk of
severe thunderstorms for later today.  Heavy rain may also lead to
scattered instances of flash flooding through tonight across the upper
Midwest.  The center of the system will begin to move into southern Canada
by Wednesday morning with the heavy rain threat quickly decreasing across
the Great Lakes but the winds will take extra time to subside there.

As the low pressure system begins to move away into southern Canada on
Wednesday, the trailing cold front will become nearly stationary across
the southern Plains where the next phase of severe weather and excessive
rainfall is forecast to emerge.  It appears that these threats will expand
toward the mid-Mississippi Valley Wednesday night where thunderstorms will
tend to become slow-moving.

Meanwhile, cool and unsettled weather underneath a broad upper trough is
anticipated to remain locked-in over the Northwest and Rockies through at
least midweek. Snow is possible into the higher elevations of Wyoming and
Colorado today.  Another upper trough will then bring the next round of
mountain snows and low-elevation rain into the Northwest on Wednesday
before overspreading the northern Rockies by early on Thursday where snow
levels could drop to around 7000 feet. High temperatures in these regions
are also expected to remain on the cooler side and 10 to 25 degrees below
average.

For areas south and east of the main storm system impacting the central
U.S. this week, highs are expected to soar above average and into
potentially record-breaking territory for certain spots. Widespread highs
into the 80s and low 90s are forecast from the Midwest and Deep South to
the Northeast through Wednesday, with mid-to-upper 90s and triple digits
in parts of South Texas and the southern High Plains. This heat could be
particularly dangerous for people dealing with a loss of power in parts of
Texas. Warm overnight temperatures will offer little relief and high
humidity could also lead to heat index readings over 110 degrees.

Kong/Snell


Graphics available at
https://www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php