FOUS30 KWBC 061544
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
1044 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...

16z update...No changes were made to the Marginal Risk as 12z Hi-
Res and HREF guidance remains on track for heavy rainfall risk. For
a more detailed discussion please refer to Mesoscale Precipitation
Discussion (MPD) 23 that is valid until 03z this evening. 

Gallina

---Prior Discussion---
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.

Hurley

...TN-OH Valleys into the Western Appalachians...

16z update...Ongoing convection is starting to sag southward across
southern KY into far southern WV and far western VA. This activity
is expected to continue until about 18-19z as forcing slides past
well to the northwest and activity becomes further displaced from
pool of remaining unstable (750-1000 J/kg of SBCAPE) along the 
western and central KY/TN boarder. As such, the Marginal Risk was 
trimmed across much of northern KY and WV; though a second round of
scattered thunderstorms is expected this evening just north/along 
the KY/TN border and south across Middle and eastern TN this 
evening. Similar 1.5"+/hr rates and occasional training/repeat 
environment crossing lower FFG and fairly saturated upper soil 
conditions mainly across the Cumberland Plateau into the 
Appalachians warrants maintaining the Marginal Risk here, as well.

Gallina 

---Prior Discussion---
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

$$
--- SBBSecho 3.20-Linux
 * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (618:250/1)