FOUS30 KWBC 290815
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
415 AM EDT Sun Sep 29 2024

Day 1
Valid 12Z Sun Sep 29 2024 - 12Z Mon Sep 30 2024

...THERE IS A SLIGHT RISK FOR EXCESSIVE RAINFALL FOR PORTIONS OF
THE INTERIOR MID-ATLANTIC...

...Mid-Atlantic/Central Appalachians...

Remnant moisture from Helene will remain caught up in the upper 
trough pattern across the Ohio Valley while the mean trough begins 
to slowly advance eastward through the period. During this period
precipitable water anomalies will be on the order of 1 to 2 
standard deviations above normal and will encounter increased 
forcing from the upper jet and modest lift through the column over 
much of the Mid-Atlantic. This setup will support the development 
of scattered to numerous thunderstorms that will likely have slower
storm motions. Recent rains have lowered local FFGs and increased 
sensitivity across the region. Areal average QPF for the region 
will be in the 1 to 3 inch range with isolated maximums in excess 
of 3 inches will be possible. A Slight Risk for excessive rainfall 
is in effect for extreme western Maryland, eastern West Virginia,
northern/central/south-central Virginia and north-central North 
Carolina. A Marginal Risk area spans from northeast 
Georgia/northwest South Carolina to southern Pennsylvania and 
southeast Ohio.

...Florida...

An unstable airmass coupled with lingering deep layer moisture 
will promote isolated to widely scattered thunderstorm activity 
capable of localized flooding, especially within urbanized zones.
Any of these storms will have the capability to produce 2 to 4
inches, especially along the coastline. A Marginal Risk for
excessive rainfall is in effect for central portions of the
peninsula.

Campbell


Day 2
Valid 12Z Mon Sep 30 2024 - 12Z Tue Oct 01 2024

...THERE IS A SLIGHT RISK FOR EXCESSIVE RAINFALL FOR PORTIONS OF 
THE INTERIOR MID-ATLANTIC...

High pressure to the north, and a developing surface reflection 
off the Mid-Atlantic coast thanks to the upstream trough will 
create a persistent northeasterly flow setup with greater upslope 
emphasis within the terrain across Western Virginia into the 
far eastern West Virginia. There will be an enhancement of forcing
through the column of atmosphere near the Appalachian/Blue Ridge 
spine that may result in hourly rainfall rates of 1 to 1.5 
inches/hour during this period. Soils near saturation from recent 
rains will keep the threat for flash flooding elevated for much of 
this region thus maintained a Slight Risk for excessive rainfall 
for extreme south-central Pennsylvania, western Maryland, eastern 
West Virginia and northern/central Virginia. A Marginal Risk area 
spans from northeast Tennessee/northwest North Carolina to southern
Pennsylvania.

Campbell


Day 3
Valid 12Z Tue Oct 01 2024 - 12Z Wed Oct 02 2024

The probability of rainfall exceeding flash flood guidance is less
than 5 percent.


Campbell
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