2PM Day 1 Convective Outlook for Saturday, February 14. THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF EAST/SOUTHEAST TEXAS INTO LOUISIANA AND SOUTHERN MISSISSIPPI
SUMMARY
Severe thunderstorms should develop and spread eastward late this afternoon into the evening and overnight from parts of central/east Texas to the Lower Mississippi Valley. A few tornadoes, scattered damaging winds, and isolated severe hail all appear possible.
20Z Update
Relatively minor changes were made in portions of Central Texas where stabilization has occurred behind earlier-day convection. A line of convection moving into East Texas is still expected to intensify later this afternoon as the shortwave trough progresses east and the boundary layer continues to warm/destabilize. Some semi-discrete/discrete activity also remains possible in the vicinity of San Antonio. Outflow pushing south and deep-layer shear parallel to the outflow continues to suggest large hail and damaging wind potential will remain isolated. See the previous discussion for additional information.
Central/East Texas into the Lower Mississippi Valley
A southern-stream mid/upper-level shortwave trough will continue to move quickly eastward across the southern Plains/northern Mexico today, eventually reaching the lower MS Valley tonight. At the surface, a weak low over northwest OK late this morning will develop towards the ArkLaTex by this evening while gradually deepening. An attendant cold front will sweep east-southeastward across central/east TX in tandem with the surface low, and will likely provide a focus for robust surface-based convection later this afternoon/evening. The northern extent of the surface warm sector is forecast to remain somewhat constrained by slowly eroding surface high pressure centered over the Carolinas, with a warm front expected to make only slow progress northward across LA and the central Gulf Coast States through the end of the period.
Ongoing, loosely organized convection extending from north-central to southwest TX may pose an isolated threat for hail and gusty winds through the rest of this morning into mid afternoon. With continued filtered daytime heating of a seasonably moist low-level airmass, it still appears likely that a gradual uptick in thunderstorm coverage and intensity will occur across parts of central/east TX by mid to late afternoon. Various NAM/RAP forecast soundings across this region indicate MLCAPE will likely be hindered to some extent due to saturated low-level profiles and modest mid-level lapse rates. Still, the risk for scattered severe/damaging winds should increase from late afternoon into the evening as convection gradually consolidates into a line amid strengthening low/mid-level south-southwesterly flow and related low-level/deep-layer shear. Some guidance suggests potential for a supercell or two with southward extent across central TX. If this occurs, than a locally greater threat for large hail may exist given somewhat more favorable mid-level lapse rates with southward extent amid the presence of strong deep-layer shear. However, confidence in this scenario occurring remains too limited for a Slight Risk expansion into central TX at this time.
Some risk for line-embedded tornadoes should also exist this evening into early Sunday morning from parts of east TX into LA with the bowing line, particularly as effective SRH becomes maximized with an increasing southerly low-level jet across the warm sector. The potential for pre-frontal supercells ahead of the line remains unclear. Instability is expected to become meager with eastward extent late tonight/Sunday morning along the central Gulf Coast, which should result in a gradual weakening of the line towards sunrise/the end of the period. Still, the threat for at least isolated damaging winds and perhaps a tornado or two may persist given the ample low-level shear forecast.
Western North Texas into Western/Central Oklahoma
Cold mid-level temperatures (around -16 to -18C at 500 mb) will be present across parts of western north TX into OK this afternoon as the upper trough continues eastward over the southern Plains. While residual low-level moisture and weak MUCAPE will be present beneath the upper trough, relatively modest low/mid-level winds should generally temper the threat for large hail with any widely spaced cells that can develop this afternoon.