Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1259 AM CDT Thu Mar 21 2024
Valid 211200Z - 221200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF
TEXAS AND FAR SOUTHWEST LOUISIANA...
...SUMMARY...
Isolated severe thunderstorms producing large hail and strong wind
gusts are possible from parts of far southwest Louisiana and the
Texas Coastal Plain northwestward into central and north Texas.
...Southern Plains/Sabine River Valley...
An upper-level trough will move eastward across northern Mexico
today, as an associated surface low develops and moves northeastward
along the Texas coast. A moist airmass, with surface dewpoints in
the mid to upper 60s F, will be located along the lower to middle
Texas Coast. The moist axis will extend northwestward into central
and north Texas. Moderate instability appears most likely to develop
from the lower to middle Texas coast inland about 50 statute miles.
However, weak instability sufficient for strong updrafts should
develop across most of the moist airmass by afternoon. Thunderstorms
will likely be ongoing at the start of the period, with a cluster of
convection moving northeastward from near Corpus Christi to the
Houston vicinity during the morning and early afternoon. Additional
storms are forecast to develop further northwest along and near the
moist axis during the afternoon across parts central and north
Texas. A second round of storms may impact the Texas Coastal Plain
during the evening.
Ahead of the approaching system, deep-layer shear is expected to
increase across the Texas Coastal Plain during the day. RAP forecast
soundings near Victoria increase 0-6 km shear from 35 knots at 12Z
to near 50 knots by 20Z. This increase in deep-layer shear will
likely correspond to an increase in the potential for supercells.
The thermodynamic environment over the Texas Coastal Plain is
forecast to be favorable for large hail, with 700-500 mb lapse rates
in the 7 to 7.5 C/Km range, and 500 mb temperatures around -13 to
-15C. Supercells that form will have the greatest threat for large
hail. The wind-damage threat is more uncertain, and should depend
upon the dominant storm mode. In spite of a low-level temperature
inversion evident in the forecast soundings, isolated wind damage
may occur, especially if a more persistent line segment can become
organized. A marginal tornado threat could also develop if a
supercell becomes dominant with that threat extending into far
southwest Louisiana, where low-level shear will be strong in the
afternoon.
Further northwest into parts of central and north Texas, weak
destabilization is expected by afternoon as surface temperatures
warm. An upper-level low will move into northwest Texas, where a
cold pocket aloft will create steep mid-level lapse rates. As
scattered thunderstorms increase in coverage during the afternoon,
hail will be possible within the stronger cores. The threat is
expected to be strongly tied with surface heating.
..Broyles/Flournoy.. 03/21/2024
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