Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
401 PM EDT Wed Aug 17 2022

Valid 00Z Thu Aug 18 2022 - 00Z Sat Aug 20 2022

...Flash flood risk intensifies in the Southwest as an already active
Monsoon season ramps up...

...Showers and thunderstorms remains persistant across the Southeast and
Southern Plains...

...Hot weather continues for California and the Northwest with numerous
heat advisories in place...

The flash flood risk across the Southwest associated with an already
active Monsoon season will increase further over the next couple of days
as a mid-level low associated with a former tropical wave over the Gulf of
Mexico leads to an increase in moisture and instability on top of the
Monsoonal moisture already in place. There is a Slight Risk of Excessive
Rainfall Thursday for portions of southwestern Utah and Arizona for areal
average rainfall totals between 0.5-1", with locally much higher totals
possible across far southern Arizona closer to the influence of the
mid-level low. The threat increases Friday for potentially much more
siginficant rainfall, and a Moderate Risk has been issued for southeastern
Arizona and southwestern New Mexico. Areal average rainfall totals
increase to 2+", a notably high amount for a more widespread area which
may lead to major flood-related impacts.

Meanwhile, persistant shower and thunderstorm chances continue from the
southeast to the Southern Plains along a wavey stationary boundary which
will remain in the area through the end of the forecast period. There is a
Slight Risk of Excessive Rainfall for portions of southeastern Georgia as
well as southeastern Louisiana and southern Mississippi where more
continuous rounds of storms and high rain rates may lead to locally
heavier rainfall totals of 3+" and a few instances of flash flooding.

Outside of the heavy rainfall threat, hot weather will remain in place
across California and the Northwest under the influence of an upper-level
ridge. There are numerous heat-related advisories in effect for the
central Valleys of California, most of the interior Pacific Northwest, and
the nothern Great Basin as highs reach into the upper 90s and low 100s
Thursday and Friday. The heat threat will be most intense across the
Colubmia River Valley in central Washignton where highs up to 105 and lows
dropping only into the upper-60s and low 70s are up to 20 degrees above
normal for the region. The urban areas from Seattle south to Portland will
also see hot temperatures in the mid- to upper 90s Thursday before an
upper-level trough approaches from the Pacific and the ridge shifts
eastward, providing a return to more normal temperatures Friday and a
break from the heat.

Elsewhere, high temperatures approaching 100 along with high humidity will
lead to heat indices around 110 for portions of southeastern Texas
Thursday while highs will be around normal for the Plains and Midwest.
Persistant clouds and some rain as a low departs New England will lead to
much cooler highs in the 60s. On Friday, a cold front moving southward
through the Plains Friday will drop temepartures into the 70s for the
Northern Plains while warmer highs approaching 90 return to the
Mid-Atlantic and southern New England.

Putnam


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