Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
400 AM EDT Fri Aug 19 2022

Valid 12Z Fri Aug 19 2022 - 12Z Sun Aug 21 2022

...Significant heavy rainfall event may lead to major flash flood impacts
in the Southwest...

...More heat expected across interior California and the Pacific
Northwest...

...Thunderstorms could become severe over the Midwest later today as
thunderstorms and possible flooding rains spread across the Southeast and
then up the Mid-Atlantic by the weekend...

A significant heavy rainfall event is forecast for the Southwest as a
mid-level low and anomalously high moisture associated with a remnant
tropical wave help to enhance storm development associated with an already
active monsoon season. A Moderate Risk of Excessive Rainfall is forecast
for portions of southeastern Arizona and southwestern New Mexico today and
Saturday. Areal average rainfall totals of 2-3 inches, with locally higher
amounts approaching 5-6 inches, may lead to numerous instances of flash
flooding. Slight Risks for Excessive Rainfall are also in place for a
broader area into the Four Corners region today and the southern High
Plains Saturday as additional scattered instances of flash flooding are
possible. Areas of complex terrain, slot canyons, arroyos, and burn scars
are especially vulnerable for flash flooding. By Saturday night into
Sunday morning, the focus of heavy rain is forecast to shift eastward into
the southern High Plains toward the Texas Panhandle.

Meanwhile along the West Coast, hot weather will persist from California
northward into the Pacific Northwest under the influence of an upper-level
ridge. Numerous heat-related advisories are in place as temperatures are
forecast to reach into the upper 90s to low 100s today for portions of the
interior Pacific Northwest and northern Great Basin. As an upper-level
trough approaches from the west, temperatures will cool a bit Saturday
with highs in the low to mid-90s. Further south in the central valleys of
California, the heat is forecast to peak on Saturday where afternoon
temperatures are expected to reach into the low to mid-100s.

Widespread showers and thunderstorms will continue along a wavy,
stationary front stretching from the Southeast into the southern Plains
and also with a frontal system moving from the northern Plains into the
Midwest into the weekend. The greatest chance for some scattered instances
of flash flooding is forecast for coastal plains of the South Carolina
today. Meanwhile, instability associated with an upper low rotating across
the northern Plains toward the Midwest could trigger severe thunderstorms
later today into tonight from Iowa into northern Missouri and western
Illinois.  This system will likely trigger additional strong to severe
thunderstorms as it approaches the Great Lakes later Saturday into Sunday
morning.

Elsewhere, well below normal high temperatures in the 70s to low 80s are
forecast for most of the Southwest, Great Basin, and southern Rockies due
to the widespread clouds and rain. Below normal highs are also forecast
for the Southeast (low to mid-80s) and for the Northern Plains (low to
mid-70s) under the upper low, with temperatures increasing a few degrees
closer to normal Saturday. Hotter temperatures in the upper 80s to around
90 degrees will return to the Mid-Atlantic and New England with otherwise
tranquil conditions expected into the weekend.

Kong/Putnam


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