Subj : MESO: Nws Weather Prediction Center College Park Md
To   : wx-storm@lists.illinois.edu
From : COD Weather Processor
Date : Thu Dec 29 2022 22:30:37

AWUS01 KWNH 292230
FFGMPD
LAZ000-ARZ000-TXZ000-OKZ000-300429-

Mesoscale Precipitation Discussion 1175
NWS Weather Prediction Center College Park MD
529 PM EST Thu Dec 29 2022

Areas affected...portions of eastern TX & the ArkLaTex

Concerning...Heavy rainfall...Flash flooding possible

Valid 292229Z - 300429Z

Summary...Thunderstorms are increasing in coverage and beginning
to align across portions of eastern TX.  Hourly totals to 2.5"
with local amounts of 5" are possible through 04z.

Discussion...Thunderstorms across central TX are beginning to
produce 2"+ an hour rain totals per radar estimates near Bastrop
and Giddings TX near a pre-frontal trough/leading edge of dew
point fall, with a general upward swing in coverage noted on radar
reflectivity across eastern TX.  Cloud tops are cooling as well.=20
A second band appears to be setting up closer to Shreveport LA and
the western LA/AR border.  Precipitable water values have been
rising quickly, and are up to ~1.3" near this activity per GPS
data.  When combined with 1000-500 hPa thickness values near 561
dm, the atmosphere is almost completely saturated.  Inflow at 850
hPa is out of the south-southwest at ~25 kts per VAD wind
profiles.  Effective bulk shear is ~40 kts, which when combined
with the deep layer south-southwest flow is organizing convection
into a lengthening band.  ML CAPE is 1000-1500 J/kg per SPC
mesoanalyses, with some uptick noted over the past several hours.=20
Upper level divergence is being aided both by an upper level
trough moving through the central Plains and an apparent shortwave
moving towards the region from northeast Mexico.

Mesoscale guidance indicates that hourly and overall rain totals
should be broadening across eastern TX into the ArkLaTex due to
this band.  In a few hours, it is possible that outflow boundaries
could lead to some eastward drift, which appears to be indicated
in the 18z HREF guidance.  An earlier band across west-central LA
produced local amounts of 5" -- so no reason why isolated spots in
eastern TX couldn't receive the same.  Hourly totals to 2.5" are
possible where cells train, merge, and/or mesocyclones manage to
form to hold up any forward propagation in a few hours.  These
totals would be most problematic in urban areas.

Roth

....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!=
DZ3fjg!_h0zpeoumiygrTrIDMZJlxsbdzqpYGKzc9VHQdHn8G7Oe_SVfSJ1D7ODYMlzjcIihnSp=
mAUToYp73ENglHPVvvkhjrk$  for graphic product...

ATTN...WFO...EWX...FWD...HGX...SHV...

ATTN...RFC...ABRFC...LMRFC...WGRFC...NWC...

LAT...LON   33959421 33849355 33279307 31019466 29999731=20
            31329650 33409487=20

=3D =3D =3D
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