Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
346 AM EDT Mon Sep 25 2023

Valid 12Z Mon Sep 25 2023 - 12Z Wed Sep 27 2023

...Heavy rain and the potential for scattered flash flooding exists over
parts of the Upper Midwest through Tuesday...

...Unsettled weather pattern with daily chances for widely scattered
thunderstorms to set up over Florida this week...

...A few rounds of moderate to locally heavy rainfall forecast throughout
northern California and the Pacific Northwest into midweek...

The start to a new workweek will include a few pockets of showers and
thunderstorms, but generally feature a tame fall weather pattern across
CONUS. A slow-moving low pressure system spinning in the Upper Midwest
today will help spark scattered showers and thunderstorms across the
region. Since these storms are likely to move relatively slowly and
potentially contain intense rainfall rates, instances of flash flooding
are possible. The greatest chances for heavy rain is forecast today across
far southeast Minnesota, northeast Iowa, and southwest Wisconsin. Here, a
Slight Risk (level 2/4) of Excessive Rainfall has been issued. Rainfall
chances will slide southeastward with this system on Tuesday over the
Midwest, with more chances for locally intense rainfall rates, and
eventually enter the Ohio Valley on Wednesday.

Farther south along a stalled frontal boundary, isolated thunderstorms
could turn severe today across southern Texas. Large and hail and damaging
wind gusts are possible, as well as locally heavy rain. Meanwhile, Florida
is also expected to be an area where increasing thunderstorm activity
could lead to localized severe storms. The unsettled weather pattern over
the Sunshine State is expected to become more pronounced as the week goes
on, with greater coverage of thunderstorms capable of containing intense
rainfall rates and frequent lightning. A Marginal Risk (level 1/4) of
Excessive Rainfall has been issued for Tuesday and Wednesday over much of
Florida as well as into parts of southern Georgia, with urban areas most
at risk for rapid water rises during downpours.

A very strong low pressure system churning over the northeast Pacific
Ocean has helped usher in early season beneficial rainfall to much of the
Pacific Northwest and northern California. Moderate to locally heavy rain
spreading inland today along a cold front is expected to impact areas of
Oregon and Washington experiencing severe to extreme drought conditions.
Another round of locally heavy rain embedded within continuous rounds of
scattered showers is forecast to enter the region late Tuesday night into
early Wednesday. One area where too much rain could lead to localized
flooding concerns is across southwest Oregon and northern California. This
is due to recent burn scars in the area that are unable to retain heavy
rainfall, potentially leading to debris flows.

Temperatures are anticipated to remain well below average through
Wednesday across the Mid-Atlantic and West Coast, where a combination of
rain, wind, and cloud cover will keep temperatures cool. A coastal storm
gradually exiting into the western Atlantic Ocean while underneath a
potent high pressure system building over eastern Canada will help funnel
easterly winds and light rain into the Mid-Atlantic, with some embedded
heavier showers over parts of Long Island and southern Connecticut today.
Conversely, above average temperatures are forecast over much of the
central U.S. (spanning from the northern High Plains to the Mid-South),
where highs into the 80s and low 90s will be common.

Snell

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