962 ACUS02 KWNS 140521 SWODY2 SPC AC 140519 Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1219 AM CDT Wed Apr 14 2021 Valid 151200Z - 161200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM WEST-CENTRAL TEXAS TO THE CENTRAL GULF COAST... ...SUMMARY... 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. ...Synopsis... 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 time. ..Leitman.. 04/14/2021 $$
