Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
441 AM EDT Sun Oct 01 2023

Day 1
Valid 12Z Sun Oct 01 2023 - 12Z Mon Oct 02 2023

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE FLORIDA PENINSULA...

...Florida...

We've upgraded the Florida Marginal to a Slight Risk. There's been
a consistent signal for heavy rain to occur over central/southern
Florida's Atlantic coast for a couple days now, but the signal has
increased significantly over the last few runs. PWATs will be well
over 2 inches with some shallow instability. The presence of a
surface front will allow for thunderstorms to continuously develop
and dissipate through the afternoon. HREF 24 hour exceedance
probabilities of 5" are quite high as well.

...New Mexico/west Texas...

The deep diffluent pattern over the Great Plains will continue to
generate convection in the Southern Plains on Sunday. Instability
around 1000J/Kg and PWATs of over 1" could support some instances
of flash flooding this afternoon and evening. The global models
appear to be well clustered over the Southern High Plains as well,
however the GFS appear to suggest that the heaviest rainfall will
be scattered across the marginal risk area, so an upgrade is not
necessary at this time. Ensemble mean exceedance probabilities of
1" and 2" in 24 hours including the 00z GEFS are well clustered
over the northeastern New Mexico and the Texas panhandle.


Kebede


Day 2
Valid 12Z Mon Oct 02 2023 - 12Z Tue Oct 03 2023

...THERE IS A SLIGHT RISK OF EXCESSIVE RAINFALL OVER PORTIONS OF
THE SOUTHERN HIGH PLAINS OF NEW MEXICO AND TEXAS...

...Southern High Plains of New Mexico and Texas...

Confidence has increased enough to warrant an upgrade of the New
Mexico/west Texas Marginal to a Slight Risk. The Southern High
Plains will be under the influence of deep diffluent flow from a
potent upper trough propagating through the West on Monday. This
will be coupled with the arrival of a strong upper jet aloft and
favorable low level jet dynamics. Cape values in the 1000-1500J/Kg
range and moisture anomalies well over 2 standard deviations
(1-1.5in") should support thunderstorm activity (some severe) with
excessive rainfall potential.

...Florida...

Albeit weaker than today's threat, Monday's heavy rainfall threat
will shift to southern Florida as the surface front, which will
continue to be the focus for storms, shifts southward. Instability
will weaken on Monday so any excessive rainfall threats will
likely be few and far between. The main threat from potential
heavy rainfall will be over urban areas.


Kebede

Day 3

The Day 3 outlook will be updated by 0830Z.


Day 1 threat area: www.wpc.ncep.noaa.gov/qpf/94epoints.txt
Day 2 threat area: www.wpc.ncep.noaa.gov/qpf/98epoints.txt
Day 3 threat area: www.wpc.ncep.noaa.gov/qpf/99epoints.txt