Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
358 AM EDT Mon Sep 18 2023

Valid 12Z Mon Sep 18 2023 - 12Z Wed Sep 20 2023

...Heavy rainfall with localized flash flooding possible for New England
Monday...

...Heavy rain and severe storm chances return to parts of the Southern
Plains on Tuesday...

...Hot late Summer temperatures for the heartland to start the week...

Shower and storm chances should diminish for much of the East Coast this
morning as a pair of frontal systems push off into the Atlantic. However,
an organizing low pressure system just off the coast will track northward
towards New England, helping to funnel warm, very moist air into the
region. Widespread moderate to locally heavy rainfall is forecast to push
northward through much of New England through the day Monday, with the
most consistent, heaviest rainfall expected closer to the Atlantic Coast.
A Slight Risk of Excessive Rainfall (level 2/4) has been introduced for
portions of coastal and Downeast Maine where wetter antecedent conditions,
including rainfall associated with Lee this past weekend, will lead to a
locally higher chance for some scattered instances of flash flooding. Rain
chances should clear from south to north through early Tuesday morning.
Additionally, wet weather is expected across much of the central and
southern Florida Peninsula as the slow-moving cold front lingers over the
region, sparking widespread daily thunderstorm chances early this week.
Forecast highs are generally below average broadly across the East
following the frontal passages, with 60s and 70s from the Midwest to the
Northeast, upper 70s to mid-80s for the Southeast, and upper 80s to low
90s for Florida. 

A subtle upper-level wave is forecast to eject eastward from the Rockies
over the Southern Plains Tuesday, passing over very moist southerly return
flow from the Gulf of Mexico and interacting with a lingering frontal
boundary, leading to increased shower and thunderstorm chances by Tuesday
afternoon. The Storm Prediction Center has issued a Slight Risk (level
2/5) of severe thunderstorms from northwest Texas into Oklahoma as some of
the more robust initial storms may produce some large hail and damaging
wind gusts. In addition, the potential for very heavy downpours as well as
for storms to congeal into more widespread clusters into the evening hours
may lead to some flash flood risk, and a Slight Risk of Excessive Rainfall
has been introduced.

An upper-level ridge shifting eastward over the Plains will continue to
lead to unseasonably hot late Summer high temperatures for much of the
heartland to start the week. Forecast highs are in the 80s to low 90s
broadly across the Central and Northern Plains with low to mid-90s
expected for the Southern Plains and Lower Mississippi Valley. These highs
will be running 10-20 degrees above average, particularly over the
Northern Plains. An upper-level wave/cold front pushing eastward from the
Pacific Northwest will begin to bring some cooler, more seasonable
temperatures to northern portions of the High Plains on Tuesday, with 70s
forecast. Conditions will be mostly dry broadly across the western and
central U.S. outside of the aforementioned storm chances over the Southern
Plains. The combination of hot temperatures, low humidity, and gusty winds
have promoted a Critical Risk of Fire Weather (level 2/3) from the Storm
Prediction Center for portions of the Northern High Plains Monday. Highs
in the 60s and 70s will be a bit below average for the Pacific Northwest
and coastal California. Seasonable highs in the 80s are forecast for
central California into the Great Basin with 90s expected for the Desert
Southwest.

Putnam

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