SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0741 AM CDT Mon May 12 2025 Valid 121300Z - 131200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS EASTERN MONTANA AND NORTHWEST NORTH DAKOTA... ...SUMMARY... Isolated severe thunderstorms are possible across parts of the Southeast today, where a tornado or two, localized damaging winds, and hail could occur. Isolated severe wind gusts are also possible in northeast Montana to northwest North Dakota around early evening. ...Southeast States... The persistent vertically stacked mid/upper low that has been nearly stationary over the Sabine Valley/Lower Mississippi River Valley will finally accelerate northeastward towards western Tennessee through tonight. A jetlet of cyclonically curved mid-level southerlies over the northeast Gulf and Florida Panhandle will dampen somewhat as it becomes centered on north Florida to southeast Georgia vicinity this afternoon. More probable diurnal thunderstorm development is anticipated from the left-exit region of this jetlet westward towards the cold-core of the stacked low. Deep-layer vertical shear will relax with westward extent, yielding more of a pulse strong-storm environment from Middle Tennessee to western Alabama and Mississippi. Despite the meridional deep-layer wind profile, effective shear should be sufficient for multicell clusters and transient updraft rotation centered on eastern Alabama and Georgia into north Florida. Pockets of modest buoyancy should support a mix of small to marginally severe hail and strong gusts capable of isolated damaging winds. Along the eastern periphery of this activity, a tornado or two is possible where there remains some overlap with the western belt of enhanced low-level flow, including South Carolina into both western and near-coastal North Carolina. Farther south, a more nebulous convective scenario is anticipated amid extensive ongoing convection across the Florida Peninsula and Keys. Guidance differs markedly with the degree of destabilization, as adequate boundary-layer heating will be required amid poor mid-level lapse rates near 5 C/km. But some guidance suggests south-central/southern Florida has the best chance at recovery by afternoon, although low-level winds will tend to be veering with a likely diminishing trend of low-level SRH. ...Northeast Montana/northwest North Dakota... Another day of rather deeply mixed thermodynamic profiles is expected across the region. Isolated thunderstorms are most probable from mid-afternoon into evening with development near/behind an eastward-advancing front. Overall convective coverage off the higher terrain of southern Montana should be substantially less than in recent days, amid deep-layer southwesterly wind profiles. The potential will exist for a few dry microbursts producing localized severe-caliber wind gusts. ..Guyer/Dean.. 05/12/2025