Subj : HVYRAIN: Excessive Rainfall Discussion
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Fri Jan 27 2023 08:25:29

FOUS30 KWBC 270825
QPFERD

Excessive Rainfall Discussion
NWS Weather Prediction Center College Park MD
324 AM EST Fri Jan 27 2023

Day 1
Valid 12Z Fri Jan 27 2023 - 12Z Sat Jan 28 2023

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

Wegman



Day 2
Valid 12Z Fri Jan 27 2023 - 12Z Sat Jan 28 2023

....THERE IS A MARGINAL RISK OF EXCESSIVE RAINFALL FOR PORTIONS OF
SOUTHEAST TEXAS & SOUTHWEST LOUISIANA...

A digging longwave positively-tilted trough will direct a
weakening shortwave across the Red River Valley and into the
Ozarks Saturday night. Meanwhile, deep Gulf moisture will be
directed northward from the Bay of Campeche into eastern TX and
southwest LA, as a front pushes south and east out of the Plains
and into northeast TX through AR. As is typical of most January
nights, instability will be the primary limiting factor. MUCAPE
across AR will struggle to even get to 100 J/kg. Meanwhile we'll
be doing a bit better in that arena further south, especially
across southeast TX. Thus, the main change from inherited was to
remove the Marginal Risk across much of AR in favor of areas
closer to the Gulf Coast. In deference specifically towards the
GEM Regional, which is typically a reasonably accurate
representation of convective potential around the Gulf Coast, much
of the Marginal Risk area was retained across southeast TX and
southwest LA. Besides greater instability, the GEM-REG indicates
the potential for multiple inches of rain from training convection
in the Marginal risk area.

Antecedent conditions remain favorable in the Marginal Risk area
with nearly saturated soils, though that may be mitigated somewhat
by the dry conditions expected between now and Saturday night.
PWATs will increase Saturday to 1.5" along the TX Gulf Coast,
which is over 2 sigma above normal for this time of year. The LLJ
will increase to 50 kt across northern LA/southern AR, while
further south in the Marginal Risk area, expect the LLJ to be
closer to 30 kt. Nonetheless this will advect plentiful Gulf
moisture into the area which will support training convection.
While the forcing will be greater further north, again the lack of
instability should disallow short-term heavy rainfall rates, even
if there are training cells into southern AR.

Wegman

Day 3

The Day 3 outlook will be updated by 0830Z.


Day 1 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=
v/qpf/94epoints.txt__;!!DZ3fjg!8yCGl5RgCxfUCezfYXSz2lh8XaWxxW8dYp-MTq8tcuPP=
VyIr2AG8WJYgn_rbpqd845vBNPLfg6wEvonHopsBkriBW60$=20
Day 2 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=
v/qpf/98epoints.txt__;!!DZ3fjg!8yCGl5RgCxfUCezfYXSz2lh8XaWxxW8dYp-MTq8tcuPP=
VyIr2AG8WJYgn_rbpqd845vBNPLfg6wEvonHopsB2hjXzWA$=20
Day 3 threat area: https://urldefense.com/v3/__https://www.wpc.ncep.noaa.go=
v/qpf/99epoints.txt__;!!DZ3fjg!8yCGl5RgCxfUCezfYXSz2lh8XaWxxW8dYp-MTq8tcuPP=
VyIr2AG8WJYgn_rbpqd845vBNPLfg6wEvonHopsBjU08oAQ$=20


$$



=3D =3D =3D
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