SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0754 AM CDT Sun May 11 2025 Valid 111300Z - 121200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE NORTHERN ROCKIES AND MONTANA HIGH PLAINS... ...SUMMARY... Scattered severe wind gusts are expected across the northern Rockies to Montana High Plains fom mid-afternoon into the evening. Isolated severe thunderstorms are also possible across the Southeast today through tonight. ...Northern Rockies/High Plains and northeast Great Basin... The leading portion of an eastward-transitioning upper-level trough will overspread the northern Rockies and northern Great Basin later today and tonight, with preceding height falls and a regionally strengthening 60-80 kt southwesterly mid-level jet. These trends in conjunction with orographic influences/differential heating will lead to another round of isolated to scattered thunderstorms by mid/late afternoon. Similar to Saturday, severe-caliber wind gusts will be the primary hazard as storms develop in association with deeply mixed boundary layers, especially with eastward extent from southeast Idaho to central/eastern Montana. Corridors of modest buoyancy, coupled with moderate to strong deep-layer southwesterly speed shear, could yield a few high-based supercell structures producing small to marginally severe hail. This should be focused from the Oregon/Washington/Idaho border vicinity into central Montana, and separately over southeast Idaho into Yellowstone. ...Southeast States... A persistent, slow-moving, and essentially vertically stacked low will persist, centered over the ArkLaMiss vicinity, with a preceding belt of moderately strong mid-level winds extending over the northeast Gulf to the coastal Southeast. This will overlie a moderately moist warm sector to the east of the surface cyclone and along/south of the eastward-extending stationary front (or slow-moving warm front). Scattered thunderstorms are ongoing regionally this morning, including semi-extensively over the northeast Gulf. A 30-40 kt southerly low-level jet is expected to sustain adequately enlarged low-level hodographs within this corridor, but especially towards the coast and near the warm front. But convection is expected to be within a messy, outflow-dominated mode at times. Regardless, isolated damaging wind and tornado potential is apparent. While the severe risk does not appear as semi-focused as yesterday, portions of far northern Florida to southern/southeast Georgia in vicinity of the stationary/warm front will be reevaluated for a potential Slight Risk upgrade. Farther west in Alabama and Mississippi, despite somewhat cooler mid-level temperatures closer to the upper cyclone, lapse rates still appear modest. But deep-layer speed shear will be moderately favorable amid a nearly unidirectional southeasterly wind profile. A few cells may briefly produce marginally severe hail and locally strong gusts, and possibly some funnel/brief tornado potential, mainly from late afternoon through early/mid-evening. ..Guyer/Dean.. 05/11/2025