Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
439 PM EDT Thu Aug 17 2023

Valid 00Z Fri Aug 18 2023 - 00Z Sun Aug 20 2023

...Anomalous heat shifts from Northwest into Northern/Central Plains;
Widespread record breaking heat wave persists across the Southern Plains
and Lower Mississippi Valley through the weekend...

...Showers, thunderstorms, and an increasing risk of flash flooding for
the Southwest...

...Scattered showers and thunderstorms from Ohio Valley into Northeast
through Saturday...

...Critical Fire Weather Risk for portions of the Pacific Northwest and
Northern Rockies/Plains...

An amplified upper trough will close-off as it spins through the Northeast
and parts of southeastern Canada over the next couple of days. Scattered
showers and thunderstorms will focus along a surface cold front sweeping
across the Ohio Valley, northern Mid-Atlantic and Northeast. Rainfall
rates shouldn't be high enough to cause flash flooding concerns, however
marginal risks are in effect for much of the Northeast to account for any
potential isolated instances through Friday night.

Elsewhere, scattered shower and thunderstorm activity will impact portions
of the Southwest, Intermountain West and Great Basin tonight as an upper
low off the California Coast and the central U.S. ridge directs energy
into the West. More impactful moisture won't begin to arrive until Friday
afternoon when some afternoon storms may produce instances of flash
flooding over parts of northern Arizona and Southern Utah. A Slight Risk
of Excessive Rainfall is in effect for the aforementioned areas, due in
part to the presence of slot canyons, which are prone to flash flooding.
Tropical moisture is likely to arrive over the Southwest beginning
Saturday night. Heavy rainfall and thunderstorms are likely to impact
parts of Southern California into southwestern Arizona and southern Nevada
beginning Saturday night.

An upper trough will swing across southwestern Canada while an upper ridge
expands over the Great Plains and Mississippi Valley over the next couple
of days. This will support anomalous warmth to spread from the Northwest
into the Northern/Central Plains tomorrow. Lows in the mid-upper 60s and
low 70s may tie or break records across the Northwest tonight. The heat
will spread into the Plains on Friday, where high temperature anomalies
are likely to be 10-20 degrees above average. Widespread record breaking
heat is expected to persist across the Southern Plains and Lower
Mississippi Valley through this weekend. Take heat seriously! Avoid time
outdoors in the hottest time of the day and on the hottest days, and have
a way to stay hydrated.

Kebede

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