Short Range Forecast Discussion
NWS Weather Prediction Center College Park MD
357 AM EDT Wed Sep 27 2023

Valid 12Z Wed Sep 27 2023 - 12Z Fri Sep 29 2023

...Severe thunderstorms and locally heavy rain possible across portions of
the Ohio Valley today...

...Wet weather to continue across much of Florida and into the coastal
Southeast, as well as the Pacific Northwest...

...Much above average temperatures expected to build over the central U.S.
by the end of the week...

A slow-moving low pressure system over the Midwest and associated frontal
boundaries are forecast to slide eastward into the Ohio Valley today,
while spreading scattered thunderstorm chances into the region. Some
storms could become strong enough to produce hail and damaging wind gusts.
The Storm Prediction Center has issued a Slight Risk (level 2/5) for
severe weather across an area with the greatest chances for potentially
robust thunderstorms. This includes far southeast Illinois, southern
Indiana, and western/central Kentucky. Locally heavy rain may also
accompany thunderstorms and lead to isolated instances of flash flooding.
This system is expected to weaken and linger over the Ohio Valley on
Thursday, with additional chances for scattered thunderstorms.

Another region where autumn thunderstorms will be common, but lasting for
several days this week, is Florida and the nearby Southeast coastline. A
gradually sinking cold front and area of low pressure lingering off the
Southeast coast will allow for daily chances for numerous thunderstorms.
The main weather hazard is expected to be associated with heavy rain and
chances for urban flooding. Ample atmospheric moisture in place will allow
for thunderstorms to contain intense rainfall rates that could lead to
rapid water rises where rainfall runoff is impeded. A Marginal Risk (level
1/4) for Excessive Rainfall has been issued for the Sunshine State between
today and Friday. Residents and visitors are reminded to never drive
through flooded roadways.

Unsettled weather is also in store for the Pacific Northwest as a march of
low pressure systems continue through the end of the week and produce an
early taste of the region's rainy season. The first system to impact
Washington and Oregon will move onshore this morning and spread moderate
to locally heavy shower activity inland. Another weaker system will
approach the Northwest on Thursday and continue rainfall chances through
at least Friday into northern California. The few inches of rainfall
expected across parts of Washington and northwest Oregon are expected to
be mostly beneficial as the area deals with ongoing drought conditions.
Below average temperatures are also in the forecast, with highs into 60s
due to rainfall and associated cloud cover.

Below average temperatures are also anticipated to remain locked in place
over the Mid-Atlantic and New England as the final days of September loom.
The combination of a strong high pressure system over southern Quebec and
low pressure off the Southeast coast will continue persistent moist
easterly flow off the Atlantic Ocean into the region. Light rain and
drizzle may become more widespread by the end of the week, with high
temperatures remaining in the 60s and low 70s. In contrast, well above
temperatures are forecast throughout a majority of the Nation between the
East and West coasts. Highs into the 80s and 90s are expected to stretch
from the Desert Southwest to the Midwest and Mid-South. This would equate
to around 10 to 20 degrees above average throughout the central Plains and
neighboring Upper/Middle Mississippi Valleys.

Snell

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