Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
319 PM EDT Sat Jul 31 2021

Valid 00Z Sun Aug 01 2021 - 00Z Tue Aug 03 2021

...Excessive heat continues today over the interior Pacific Northwest, the
South-Central U.S., and the Deep South before a cooling trend begins in on
Sunday...

...Strong to severe thunderstorms with locally heavy rainfall from the
Central Plains and mid-Mississippi Valley to the Southeast this afternoon
reaches the Gulf Coast for Sunday and Monday...

...More rounds of monsoonal moisture expected across the interior western
U.S. with flash flooding possible from the Great Basin to the Rockies...

Oppressive summer heat has taken a vacation this weekend throughout the
Midwest, Great Lakes, and Northeast thanks to a cold front ushering in a
much cooler and drier airmass. Saturday's stifling heat across the Deep
South and Southeast will improve slightly on Sunday but a hot and humid
air-mass remains in place to close out the weekend. However, a cold front
responsible for the injection of cooler and drier conditions in the
Northeast this weekend eventually reaches the Deep South by Monday. Muggy
conditions will likely persist along the Gulf Coast while comfortable
humidity levels stick around in the Northeast and Great Lakes into start
of the work-week.

Precipitation-wise, waves of low pressure developing along an elongated
frontal boundary draped from the central High Plains to the Southeast is
forecast to trigger organized thunderstorms that could produce isolated
tornadoes, damaging wind gusts, and large hail today from Kansas to the
Carolinas. In addition, heavy downpours associated with these
thunderstorms could lead to flash flooding in the mid-Mississippi River
Valley today. The threat for severe weather and flash flooding pushes
south and east on Sunday as the cold front becomes positioned over the
Deep South. Farther north, a reinforcing shot of cooler air from Canada
ushering in a swath of showers and some storms across the Great Lakes
today reaches the Northeast by Sunday afternoon. This system will attempt
to merge with one of the aforementioned waves of low pressure reaching the
Mid-Atlantic coast by late Sunday and produce a period of strong to
possibly severe thunderstorms near the Mid-Atlantic coast. By Monday, high
pressure is in control from the Midwest to the Northeast while scattered
thunderstorms set up shop along the Gulf Coast.

In the West, a ridge of high pressure aloft has anchored itself over the
region and continues to generate excessive heat this afternoon across the
interior Pacific Northwest. An influx of monsoonal moisture being advected
in from the Southwest should cool down temps in the interior Pacific
Northwest on Sunday. Speaking of monsoonal moisture, there is no shortage
of it across the drought-stricken Intermountain West. However, there is
such a deep reservoir of monsoonal moisture available that showers and
thunderstorms are capable of producing heavy rainfall rates and could
trigger areas of flash flooding. Locations most at risk for flash flooding
are where antecedent soil conditions are overly saturated or near burn
scars. As a result, a handful of Slight risks for Excessive Rainfall are
in place from the Great Basin to the central Rockies today. The Excessive
Rainfall threat on Sunday shifts a into areas such as Bitterroots and
Snake River Valley as well as the southern High Plains. More rounds of
heavy showers and storms are possible up and down the spine of the Rockies
on Monday.

Lastly, Air Quality Alerts remain in effect for portions of Montana,
Wyoming, Minnesota, Wisconsin, Iowa, and the Tennessee Valley due to smoke
associated with raging wildfires over western North America being advected
into the regions by prevailing north-northwesterly winds.

Mullinax


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