FOUS30 KWBC 060826
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
326 AM EST Thu Feb 6 2025

Day 1
Valid 12Z Thu Feb 06 2025 - 12Z Fri Feb 07 2025

...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF CALIFORNIA AND THE OHIO VALLEY...

...California...
After a one day break another system is forecast to move into CA
today and Thursday night. Not an AR but rather a compact, dynamic 
system with a vigorous mid level shortwave and strong left exit 
region upper level jet forcing. These dynamics should support a 
short duration period of enhanced rainfall rates, although the 
quick forward motion of the system will limit overall rainfall 
magnitudes. Given the low-level ageostrophic response ahead of the 
upper level jet streak, the latest (00Z) GEFS output shows a quick 
uptick in southwesterly 850-700 mb moisture transport, peaking 
between 3-4 standard deviations above normal across the central 2/3
of CA Thursday afternoon and evening. Recent model runs continue 
to show 1-2+ inches falling mostly within 12 hours, with localized 
amounts of 3+ inches over the coastal ranges and Sierra foothills 
per the latest high-res guidance. Given the saturated conditions 
and brief potential for higher rates (0.35+ in/hr) beginning around
21Z along the coast and by 00Z farther inland, this may result in 
localized runoff issues, especially over burn scars across Santa 
Barbara, Ventura, and Los Angeles counties. 

...TN-OH Valleys into the Western Appalachians...
Another round of locally heavy rain is expected Thursday across 
portions of KY, TN, WV and far western VA- NC along and ahead of an
approaching cold front. Showers and embedded thunderstorms will be
ongoing to start the period (12Z Thu) and may periodically 
continue through the day/evening near the only slowly southward 
shifting front. While nothing significant, CAPE upwards of 500-1000
J/Kg still seems likely along this corridor, which should be 
enough to support locally heavy rainfall rates. While soil 
conditions and streamflows are returning closer to average after 
the flooding several days ago, some of this region is still likely 
more sensitive than normal to additional heavy rainfall. The latest
WPC areal-average QPF peaks between 0.75"-1.25", though per the 
CAMs, localized totals between 2-3"+ are expected, which makes 
sense given the instability forecast. Overall expect this rainfall 
to pose a localized flood risk.

Hurley


Day 2
Valid 12Z Fri Feb 07 2025 - 12Z Sat Feb 08 2025

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

Hurley


Day 3
Valid 12Z Sat Feb 08 2025 - 12Z Sun Feb 09 2025

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

Hurley
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