Subj : HVYRAIN: Excessive Rainfall Discussion
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Sat Nov 25 2023 15:54:18

FOUS30 KWBC 251554
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
1053 AM EST Sat Nov 25 2023

Day 1
Valid 16Z Sat Nov 25 2023 - 12Z Sun Nov 26 2023

....A MARGINAL RISK OF EXCESSIVE RAINFALL EXISTS FOR SOUTH
FLORIDA...

Showers and thunderstorms should attempt to attain some level of
organization near the Gold Coast this period as instability slowly
increases into the 500-1000 J/kg range in and near a coastal
front, precipitable water values lie in the 1.5-2" range, and
enough effective bulk shear is expected due to surface easterly
flow conflicting with 850-400 hPa mean westerly flow. This wind
conflict with height could help tie convection near the coast and
keep storms from showing much movement, which would be a problem
as hourly rain totals to 2.5" would be possible where storms form.
The 12z HREF has decreased it's probabilities for 3"+ amounts when
compared to its 00z run (now around 30%), with better chances for
5"+ remaining across the Gulf Stream just offshore. There is quite
the spread in the guidance here, with the global models a bit less
impressed than the mesoscale guidance. Regardless, the excessive
rainfall threat appears to be isolated and hindered on if
convection anchors onshore. Since the synoptic pattern still looks
favorable, have maintained the Marginal Risk of excessive
rainfall/flash flooding for South Florida. Isolated problems are
possible in urban areas where rain rates overwhelm drainage.

Roth/Snell


Day 2
Valid 12Z Sun Nov 26 2023 - 12Z Mon Nov 27 2023

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

Roth

Day 3
Valid 12Z Mon Nov 27 2023 - 12Z Tue Nov 28 2023

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

Roth


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=
v/qpf/94epoints.txt__;!!DZ3fjg!7UWwA53NGzuSQwuAGxAxRrbDuOJBlY423n3TQTkDafYw=
RXWMzVcXne5MmZCILfvkRaBmG0Uh3NoMeFk5bbfe_-PaUvw$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=
v/qpf/98epoints.txt__;!!DZ3fjg!7UWwA53NGzuSQwuAGxAxRrbDuOJBlY423n3TQTkDafYw=
RXWMzVcXne5MmZCILfvkRaBmG0Uh3NoMeFk5bbfeCZEXliU$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=
v/qpf/99epoints.txt__;!!DZ3fjg!7UWwA53NGzuSQwuAGxAxRrbDuOJBlY423n3TQTkDafYw=
RXWMzVcXne5MmZCILfvkRaBmG0Uh3NoMeFk5bbfe7HTXqT4$=20


$$



=3D =3D =3D
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