Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
359 AM EDT Sat Aug 20 2022

Valid 12Z Sat Aug 20 2022 - 12Z Mon Aug 22 2022

...A heavy rainfall and flash flooding event moving across Arizona and New
Mexico today is forecast to shift eastward into northern Texas Sunday and
Monday...

...Tropical Storm Four is forecast to reach southern Texas with heavy rain
and some squalls later on Sunday...

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

...Thunderstorms moving across the Midwest could be strong today; some
strong thunderstorms are also possible on Sunday as they move across the
Mid-Atlantic on Sunday...

The stage is set for southern Arizona and New Mexico to potentially
receive prolific rainfall and widespread flash flooding today as a
mid-level low and anomalously high moisture associated with a remnant
tropical wave triggers heavy rain and thunderstorms with an ongoing active
monsoon season. WPC has a Moderate Risk for excessive rainfall covering
southeast Arizona and southwest/central New Mexico, Slight Risk spanning
from western Arizona to the Texas panhandle and Marginally encompassing
those areas and into the Four Corners/Rockies region. Areal average
rainfall totals of 2-3 inches, with locally higher amounts approaching 5-7
inches, may lead to numerous instances of flash flooding. Urban locations
in addition to areas of complex terrain, slot canyons, arroyos, and burn
scars are especially vulnerable for flash flooding and can quickly turn
into very dangerous situations.

From later today into Sunday, the focus of the heavy rainfall is expected
to shift eastward into the Southern Plains and persist in proximity to a
wavy, stationary front stretching from the Southeast into the Southern
Plains. Several inches of rain are forecast along a nearly west-east axis
from the Texas Panhandle to the Gulf states, with the heaviest amounts
focusing over northeast Texas, southern Oklahoma, southern Arkansas and
northern Louisiana. Much of this part of the country has had drought
conditions, but multiple days of moderate to excessive rainfall may
quickly lead to areas of flooding. WPC parts of Southern Plains covered by
a Slight Risk for Sunday into Monday. Further north, widespread showers
and thunderstorms will continue along a frontal system moving from the
Northern Plains into the Midwest into the weekend. Instability associated
with an upper low rotating across the Midwest could trigger strong
thunderstorms later today into tonight.  This system will likely trigger
additional strong thunderstorms as it moves across the Ohio Valley on
Sunday.

The heatwave will persist over California and the Pacific Northwest.
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. Some moderating of the daily
temperatures will occur by Saturday with the approaching upper-level, with
a few degrees cool down expected. 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. In contrast, much of the
Southwest, Great Basin and Southern Rockies will be well below normal due
to the extensive cloud cover and prolonged rainfall. Daily maximum
temperatures will stay in the 70s to lower 80s. 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/Campbell


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