SPC Mar 13, 2025 2000 UTC Day 1 Convective Outlook
SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0256 PM CDT Thu Mar 13 2025 Valid 132000Z - 141200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF ALABAMA...WESTERN FLORIDA...AND SOUTHERN GEORGIA... ...SUMMARY... Isolated strong to severe thunderstorms capable of producing hail and locally damaging gusts are possible from parts of Alabama, into southwest Georgia, and the Florida Panhandle this afternoon and early evening. ...20z Update... Minimal changes were made to the MRGL risk area over parts of the Southeast, mainly to trim the western extent. Mid-level subsidence behind the weakening vort max over parts of MS/TN will tend to limit thunderstorm potential to the west through the remainder of the afternoon. To the east, increasing low-level moisture and steep lapse rates will support isolated thunderstorms with a risk for hail and sporadic damaging gusts. Elsewhere, strong mid-level height falls are expected over the western US as a powerful upper trough approaches. A few elevated thunderstorms are possible within warm air advection over the Upper Midwest ahead of shallow returning surface moisture. To the west, cool mid-level temperatures overspreading meager low-level moisture will also support isolated thunderstorm chances over a broad area from the Desert Southwest to the Rockies. Somewhat stronger, low-topped convection is possible along the cold front from southern AZ into far western NM this evening and tonight. Given the strength of the wind fields aloft, a few severe gusts will be possible. Though, the very limited buoyancy should limit the severe threat. See the previous discussion for more info. ..Lyons.. 03/13/2025 .PREV DISCUSSION... /ISSUED 1122 AM CDT Thu Mar 13 2025/ ...Southeast... A mid-level vorticity maximum over the Mid-South late this morning will become less well defined as it moves slowly eastward across the TN Valley and Southeast through the period. Stronger mid-level flow is expected to remain over southern/coastal portions of the Southeast today. But, cold mid-level temperatures (around -18 to -21 C at 500 mb per 12Z regional soundings) in conjunction with filtered daytime heating and modest low-level moistening will support weak destabilization from parts of AL into southwest GA, and the FL Panhandle. Current expectations are for isolated to scattered thunderstorms to develop across these areas through the afternoon, as modest ascent with the weakening mid-level trough moves through. Most guidance suggests that greater convective coverage may occur over parts of southeast AL into southwest GA and perhaps the FL Panhandle, in closer proximity to greater low-level moisture and the mid-level jet. With modest to sufficient deep-layer shear, clusters to marginal supercell structures could pose an isolated threat for both severe hail and damaging winds this afternoon through early evening. See Mesoscale Discussion 167 for additional details on convective development and evolution through 20Z. ...Southern Arizona... A cold front will move eastward across southern AZ today, as an upper trough progresses over the Southwest. Showers and thunderstorms are expected to spread across this region in tandem with the front. Winds aloft will be quite strong, as an 80-100 kt mid/upper-level jet max digs southward along/near the international border. Some higher momentum flow may mix to the surface, and a gust could approach severe limits within low-topped convection. However, the weak thermodynamic profile would suggest the severe threat will remain low.
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