ACUS02 KWNS 140521
SPC AC 140519

Day 2 Convective Outlook  
NWS Storm Prediction Center Norman OK
1219 AM CDT Wed Apr 14 2021

Valid 151200Z - 161200Z


Isolated strong to severe storms are possible from west-central
Texas eastward along the central Gulf Coast. Locally strong gusts
and hail will be the main hazards with this activity.


Moderate westerly deep-layer flow will persist across the southern
tier of the U.S. on Thursday. The upper low over the Great Lakes and
attendant shortwave trough extending into the TN Valley will pivot
eastward toward/just offshore from the Mid-Atlantic coast by Friday
morning. Further west, the upper low over the western states will
weaken and become an open wave as it ejects eastward into the
central/southern Plains. At the surface, low pressure will be
centered just offshore the Mid-Atlantic coast Thursday morning, with
a cold front extending southwestward over the NC/SC coastal plain,
then westward along the central Gulf Coast vicinity and southern TX.
Low-level warm advection will maintain mainly elevated thunderstorms
near the cold front during the morning and afternoon along the
central Gulf Coast vicinity. By midday into the afternoon,
additional elevated convection is expected to develop further west
across west-central TX and shift eastward through the evening toward
the middle/upper TX coasts. 

...Southern LA/MS/AL into the western FL Panhandle...

There are some differences between forecast guidance in the exact
position of the surface cold front Thursday morning, along with
where ongoing convection will be located. Some of the ongoing
convection early in the period will likely be elevated, just to the
cool side of the front. Midlevel lapse rates around 7 C/km are
forecast amid 30-40 kt effective shear. Some of the stronger cells
could produce marginally severe hail. Increasing moisture and modest
heating ahead of the south/southeastward-sagging front could result
in a few storms becoming near surface-based by late morning into the
afternoon as they approach the coast. Any surface-based convection
will pose a threat for locally damaging gusts in addition to
marginal hail.

...West-central TX to the Middle/Upper TX Coast...

A strong cap is expected to preclude surface-based convection across
the region. However, elevated thunderstorms are expected to develop
by midday due to low/midlevel warm advection and increasing ascent
as the western trough ejects eastward. Steep midlevel lapse rates
around 7-8 C/km are forecast amid supercell wind profiles, but weak
low level flow. Furthermore, steep midlevel lapse rates will
contribute to 1000-2000 J/kg MUCAPE. This should result in clusters
of storms capable of hail. The strong cap and the expected messy
storm mode will preclude higher probabilities for large hail at this

..Leitman.. 04/14/2021