The SPC is forecasting ...Severe thunderstorms expected over parts of the lower Mississippi Valley into east TX this afternoon and tonight....
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Probability of damaging thunderstorm winds or wind gusts of 50 knots or higher within 25 miles of a point. Hatched Area: 10% of greater probability of wind gusts 65 knots or greater within 25 miles of a point.
SPC AC 131952
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0252 PM CDT Sat Apr 13 2019
Valid 132000Z - 141200Z
...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS FROM FAR EASTERN
TEXAS...THROUGH CENTRAL AND NORTHERN LOUISIANA...AND INTO CENTRAL
MISSISSIPPI...
...SUMMARY...
Numerous to widespread severe thunderstorms are expected across
parts of the south-central to southeast states through tonight. The
most likely region for strong tornadoes is from east Texas to
Mississippi, with the most dangerous period for tornadoes through 8
PM CDT.
...Discussion...
The only changes made to the previous outlook include the following:
1) Removal and eastward adjustment of probabilities over eastern TX
coincident with the evolving squall line.
2) Lowering severe probabilities over central AR and removal of
probabilities over southeastern OK where cool/stable air will likely
inhibit the risk for a strong gust or marginally severe hail.
3) A small westward extension of 5-percent hail/wind probabilities
in western NC.
..Smith.. 04/13/2019
.PREV DISCUSSION... /ISSUED 1112 AM CDT Sat Apr 13 2019/
...TX to TN Valley...
No substantial changes to categorical areas with this outlook
(beyond reducing area behind the convective line in TX).
Surface cyclone near College Station should move northeast towards
northwest LA and then across the Mid-South through tonight, as a
warm front advances north from southeast TX/central LA. Parameter
space is very supportive of supercells, with persistent
warm-advection north of the front yielding a risk for large hail.
Along and south of the front, main uncertainties are longevity and
discreteness of favorable storm mode. A deeply moist boundary layer
with upper 60s to lower 70s dew points will spread north, supporting
preconvective MLCAPE ranging from 2000-3000 J/kg across southeast TX
and southern LA. Such buoyancy will be quite favorable for all forms
of severe, amid strengthening deep shear related to the approach of
the mid/upper trough. Furthermore, low-level shear vectors and
hodograph sizes will be quite large along and south of the warm
front (from the Sabine Valley eastward), with forecast soundings
yielding 250-600 J/kg effective SRH. Any sustained supercells in
this environment will be capable of significant tornadoes.
With time this evening and overnight, convection should organize
into a roughly north/south-aligned band over the Lower Mississippi
Valley region, as deep convergence becomes better-focused in the
mass response ahead of the synoptic wave. As this occurs, the main
threat in a bulk sense may become damaging wind tonight. However,
given the strong inflow-layer SRH, tornadoes still will be probable
from both embedded supercells and QLCS mesovortices.
...Central/eastern NC...
Scattered thunderstorms are expected to develop through this
afternoon, offering the potential for locally strong wind gusts and
marginally severe hail.
Mid/upper-level support will be lacking, beneath a belt of
southwesterlies aloft. But the region will straddle a low-level
moist axis characterized by surface dew points generally in the
mid/upper 60s F, supporting preconvective MLCAPE from 1000-2000
J/kg. Though low-level flow will be weak, limiting boundary-layer
shear and hodograph size, the height gradient will remain
sufficiently tight aloft to support strong storm-relative winds in
upper levels, and effective-shear around 40-45 kt. As such, a few
organized multicells and sporadic supercell structures will be
possible. Storm intensity will diminish after sunset.
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