Subj : HVYRAIN: Excessive Rainfall Discussion
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Mon Mar 06 2023 00:49:47

FOUS30 KWBC 060049
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
749 PM EST Sun Mar 05 2023

Day 1
Valid 01Z Mon Mar 06 2023 - 12Z Mon Mar 06 2023

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

Showers and thunderstorms have formed over portions of the central
Florida peninsula during the late afternoon with onshore flow in
the wake of the sea-breeze encountered modest instability and a
separate north-south oriented surface boundary near the center of
the peninsula. Recent runs of the HRRR still shows the possibility
for isolated intense rain rates within the merging/colliding
convective clusters through about 03Z or so before the rates
weaken and activity shifts back closer to the east coast.
However...given the isolated nature of the short-lived cores of
heaviest rainfall and the relatively dry conditions should keep
any flooding issues mostly nuisance with isolated instances of
minor urban flooding runoff. No risk area was defined with this
update.

Taylor/Bann




Day 2
Valid 12Z Mon Mar 06 2023 - 12Z Tue Mar 07 2023

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

Taylor


Day 3
Valid 12Z Tue Mar 07 2023 - 12Z Wed Mar 08 2023

....THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
THE SOUTHERN PLAINS AND MIDDLE/LOWER MISSISSIPPI VALLEY...

The upper-level pattern over the CONUS will be slowly amplifying
Tuesday as a broad trough remains in place over the West and weak
ridging begins to build downstream over the Mississippi Valley,
with southwest flow in place over the central CONUS. At the
surface, a front will be pushing southward over the Middle/Lower
Mississippi Valley and Southern Plains overnight Monday and into
the day Tuesday, eventually slowing and likely becoming stationary
in the vicinity of the Red River Valley. Precipitable water
anomalies across the region begin to increase by Tuesday evening
into early Wednesday morning 2-2.5 standard deviations above the
mean as a combination of return flow moisture from the Gulf of
Mexico as well as an additional moisture stream to the southwest
from the Pacific meet over the Southern Plains.

Storms are expected to develop and increase in coverage late
Tuesday evening into the early morning hours Wednesday as
convergence and lift increase along and over the generally
east-west stationary boundary ahead of a weak surface wave and
also an inverted surface trough extending to the north. The most
recent model guidance continues to cluster around areal averages
of 0.5-1" across portions of the outlook area while the
environmental ingredients and setup suggest potential for isolated
2-3" totals possible, particularly by the end of the period. There
remains some uncertainties in the placement of the heaviest
rainfall however, so confidence in introducing a Slight Risk
wasn't high enough for this update. Recent NASA SPoRT soil
moisture anomalies in the 0-40 cm layer (moisture percentiles
80-95%) indicate some increased sensitivity to heavy rainfall so
as confidence increases, an upgrade to a Slight Risk may be
warranted for scattered instances of flash flooding.

Putnam/Taylor


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=
v/qpf/94epoints.txt__;!!DZ3fjg!_hRJRx_0fq2x6RXGUiBD1ceHMRcuXDJyN9OLiMmTWoJW=
dOT5gBqg7dR2cnnu0zWtvZMF-Pb7JYvdW9KQgM4zn7IVRsU$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=
v/qpf/98epoints.txt__;!!DZ3fjg!_hRJRx_0fq2x6RXGUiBD1ceHMRcuXDJyN9OLiMmTWoJW=
dOT5gBqg7dR2cnnu0zWtvZMF-Pb7JYvdW9KQgM4zEdi-4uk$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=
v/qpf/99epoints.txt__;!!DZ3fjg!_hRJRx_0fq2x6RXGUiBD1ceHMRcuXDJyN9OLiMmTWoJW=
dOT5gBqg7dR2cnnu0zWtvZMF-Pb7JYvdW9KQgM4zv22lJYo$=20


$$



=3D =3D =3D
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