SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1134 AM CDT Sat Mar 29 2025 Valid 291630Z - 301200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE CENTRAL AND SOUTHERN GREAT PLAINS INTO THE MIDDLE MISSISSIPPI VALLEY... ...SUMMARY... Scattered severe thunderstorms are possible across parts of the central/southern Plains into the mid Mississippi Valley, mainly this evening through the overnight hours. This may include an organized thunderstorm cluster across parts of Oklahoma into southeastern Kansas and western Missouri capable of producing very large hail, damaging winds, and perhaps a couple of tornadoes. ...Central/Southern Plains into the Mid Mississippi Valley... Water-vapor imagery shows a lead disturbance moving northeastward across the central Great Plains towards the Upper Midwest, while an upstream disturbance moves from eastern AZ into the southern Great Plains tonight. The primary surface low over western KS this morning is forecast to develop east-northeastward towards southern IA/northern MO by tonight. An attendant cold front will sweep southward across parts of the central/southern Plains through the period, while a dryline mixes eastward over the southern High Plains this afternoon. Surface analysis shows lower 60s dewpoints streaming northward on southerly low-level flow this morning from north TX to the KS/OK border. A substantial cap will likely inhibit robust convective development until late this afternoon or early evening, with the cold front/dryline intersection over western OK a potential location for convective initiation by 23-03Z as large-scale ascent with the trailing shortwave trough overspreads the warm sector. Moderate to strong buoyancy will likely be present across western/northern OK and southern KS, with steep mid-level lapse rates atop upper 50s to mid 60s surface dewpoints. Forecast soundings favor supercell development with activity that develops south of the front across west-central OK. Large to very large hail (potentially up to 1.5-2.5 inches in diameter) may accompany these storms early in their convective life cycle. Despite increasing CINH during the evening, lower 60s dewpoints in place with 500-mb temperatures around -15 deg C may aid the development of a tornado risk from central into northeast OK as storms mature and eventually grow upscale. Severe gusts will probably become more prevalent with time as this cluster moves east-northeast into parts of northeast OK and eventually into MO later tonight, perhaps with the wind threat slowly diminishing late. Farther south, a conditional severe threat exists south of the Red River from north TX southwestward into parts of the Concho Valley. It appears the airmass will remain capped during the day in the vicinity of the dryline, with storm development likely delayed until late evening into the overnight per recent model guidance. Very steep 700-500 mb lapse rates, strong deep-layer shear magnitudes (50 kt effective shear), and 2000-3000 J/kg MUCAPE will support a severe risk with any sustained storms. Models vary between very isolated coverage and scattered storm coverage, especially over parts of central into north TX. Given consistency in some model guidance (e.g., HRRR model run to run, GFS, ECMWF) showing some convective signal, have opted to increase hail probabilities to level-2 Slight Risk overnight. Large to very large hail is possible with the stronger storms (1 to 2.5 inches in diameter). ...Louisiana/Mississippi... A remnant MCV will continue to move northeastward this afternoon across the lower MS Valley and Mid-South. Although deep-layer shear is expected to remain fairly weak, sufficient low-level shear should be present to support some updraft organization and transient rotation with the stronger storms. Cells moving northeastward and inland over the central Gulf Coast may pose a threat for a brief tornado, as well as a localized risk for damaging gusts. ..Smith/Dean.. 03/29/2025