FOUS30 KWBC 090808
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
308 AM EST Sun Feb 9 2025

Day 1
Valid 12Z Sun Feb 09 2025 - 12Z Mon Feb 10 2025

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

Hurley


Day 2
Valid 12Z Mon Feb 10 2025 - 12Z Tue Feb 11 2025

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

Hurley


Day 3
Valid 12Z Tue Feb 11 2025 - 12Z Wed Feb 12 2025

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL FROM PORTIONS OF 
THE MID-SOUTH AND LOWER MISSISSIPPI VALLEY INTO THE TENNESSEE VALLEY...

...ArkLaTex-ArkLaMis into the Mid-South and Tennessee Valley...
Strong NW-SE upper level jet streak will dive southeast into CA
late on Day 3 (Tue night) -- on the western periphery of the 
longwave trough towards the base. As this occurs, the broad western
U.S. trough will amplify, thereby enhancing the deep-layer ascent
and southwesterly flow/moisture transport within a maturing Warm 
Conveyor Belt (WCB) downstream across the Mid South-Lower MS Valley
and TN Valley. 850-700 mb moisture flux anomalies increase to 2-3 
standard deviations above normal Tue-Tue night, while TPW values 
climb to 1.5-1.75" (around +2 standard deviation above normal). The
strengthening dynamical and thermodynamical support will make for 
efficient rainfall rates despite the lack of deep-layer 
instability. Much of the guidance, non-CAM at this point being a 
Day 3 forecast, depicts a widespread swath of 1.5-2.5" of rain 
within the outlook areas, with more stripes of >3" within the 
Slight Risk area. Storm motions nearly parallel to the WSW-ENE 
oriented surface boundary will boost the potential for training, 
and even though currently the non-CAM guidance is advertising 
meager deep-layer elevated instability (MUCAPEs generally 250-500 
J/Kg), believe these values will be amplified somewhat as the event
gets within the high-res CAM windows, again given the dynamic and
thermodynamic response to the broad-scale upper trough amplification.

2.00"+/3hr rainfall rates are anticipated where the cells do 
train, again most likely within the Slight Risk area, which could 
lead to localized-scattered instances of flash flooding.

Hurley

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