FOUS30 KWBC 030815
QPFERD
Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
314 AM EST Sun Mar 03 2024
Day 1
Valid 12Z Sun Mar 03 2024 - 12Z Mon Mar 04 2024
The probability of rainfall exceeding flash flood guidance is less
than 5 percent.
Hurley
Day 2
Valid 12Z Mon Mar 04 2024 - 12Z Tue Mar 05 2024
...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PORTIONS
OF THE LOWER MISSISSIPPI VALLEY TO THE CENTRAL GULF COAST...
00Z guidance continues to show showers and thunderstorms
developing on Monday and growing upscale in areal coverage and
rainfall rates from Monday night into early Tuesday. Shortwave
energy will spread into the Lower MS Valley and Central Gulf Coast
region in association with an elongated southern stream jet
sweeping eastward along the U.S. border with Mexico. This allows
for increasing flow of Gulf moisture at low levels to be drawn
inland. One concern continues to be that moisture flux standard
anomalies barely exceed 1 standardized anomaly greater than
climatology, but precipitable water values at or above 1.75 inches
and MUCAPEs on the order of 1000 J/Kg per kg hugging the Gulf
coast suggests localized rainfall rates of 2-3 inches within 2-3
hours possible, especially where quasi-linear segments off the
Gulf train. This scenario could pose an isolated flash flood risk,
mainly across urban and other poor-drainage areas. As a result,
only minor tweaks were made to the previously issued Marginal Risk
area, mainly to shift the outlook a little farther westward given
the slightly slower trends per the non-CMC guidance. Either way,
the forecast confidence remains low given the continued high
spread with the model QPFs (both placement and timing).
Hurley/Bann
Day 3
Valid 12Z Tue Mar 05 2024 - 12Z Wed Mar 06 2024
...THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL ACROSS PARTS OF
THE SOUTHEAST AND CENTRAL-EASTERN GULF COAST...
The southern stream shortwave trough across the Central Gulf Coast
region early Tuesday will become more negatively tilted as it
pivots across the Southeast and southern Appalachians later
Tuesday and Tuesday night. The shortwave energy aloft and surface low/associated
fronts will be fairly progressive, which again is a
contributing factor in the more limited (Marginal) excessive
rainfall threat as with the Day 2 outlook. 850-700 mb moisture
flux anomalies peak between 1-1.5 standard deviations above normal
per the GEFS, while PWs climb to ~1.75" along/near the coast.
Availability of deep-layer instability is a bit more nebulous
given the lack of model consensus, while the relatively
progressive synoptic features point to a more limited excessive
rainfall threat. However, the rapid increase in deep-layer
moisture (TPW standardized anomalies reaching +2 per the GEFS)
would support the potential for rainfall rates of 2-3+" in 2-3
hours where convective segments can align and train.
Hurley
$$
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