Day 1 Severe Weather Outlook

Valid 292000Z – 301200Z


A few severe thunderstorms are possible this afternoon and evening
across parts of Mississippi, northwest Alabama, and western/middle
Tennessee. Damaging winds and isolated tornadoes are the main

…20Z Update…

…Lower MS Valley into TN Valley…
Recent surface analysis places a low over central LA, very near ESF
(Alexandria, LA). Two-hour pressure falls of 3 to 5 mb downstream at
HEZ and TVR (along the LA/MS border) and at JAN (in central MS)
indicate a continued northeasterly motion of this low along the
front is likely, eventually bringing it through central MS into
northeast MS and western TN.

The convection near this low has been gradually intensifying as
instability slowly increases within the downstream air mass. Highest
probability of strong to occasionally severe thunderstorms will
likely remain close to (and just south of) this low as it enhances
ascent amidst the only modestly unstable environment. Recent KDGX
VAD data shows a very strong wind profile with winds of 40 kt at
2kft. These very long hodographs and 60 kt of 0-6 km bulk shear
will support storm organization once updrafts become deep enough.

Additional information about the severe weather threat across this
region is available in MCD 2238.

..Mosier.. 12/29/2019

.PREV DISCUSSION… /ISSUED 1007 AM CST Sun Dec 29 2019/

…Lower MS Valley into TN Valley…
Morning water vapor loop shows a vigorous shortwave trough rotating
across west central TX. Strong large-scale ascent ahead of this
feature is resulting in scattered thunderstorm activity over the
upper TX coast and parts of LA. A surface baroclinic zone extends
from this area northeastward into middle TN. 12z model guidance
continues to forecast the development of a mesolow along the
boundary, tracking from MS into TN during the afternoon and evening.
Vertical shear profiles will strengthen considerably in vicinity of
the low, resulting in a very favorable kinematic environment for
supercells and bowing structures capable of damaging winds and
tornadoes. The primary limiting factor is weak instability, with
MLCAPE generally expected to be in the 200-700 J/kg range. While
the low CAPE scenario limits confidence in a more widespread severe
event, the strength of the shear profiles and the favorable
mesoscale setup suggests some risk of a small corridor of greater
threat from northeast MS into southern middle TN during the 21-03z
time frame.


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