SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0641 AM CST Fri Jan 22 2021 Valid 221300Z - 231200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... No severe weather is expected across the U.S. today and tonight. ...Synopsis/Discussion... In mid/upper levels, a high-amplitude mean ridge will persist from the AK/Yukon border region south-southwestward to a high north- northeast of HI. To its east, a split-flow pattern is evident in moisture-channel imagery, around a compact cyclone centered near Cape Mendocino. The main/leading vorticity max will move down the coast toward MRY through 00Z, then pivot eastward across the LAS area late overnight, while weakening. Meanwhile, a trailing vorticity lobe and shortwave trough -- initially apparent offshore from Vancouver Island -- will dig south-southeastward parallel to and just off the West Coast, reaching Pacific waters west of VBG by 12Z tomorrow. Cooling aloft and related steepening of lapse rates, atop marginal low-level theta-e, may support a few weak thunderstorms ahead of the compact cyclone today over portions of central/northern CA. Strongly difluent mid/upper flow, low-level warm advection, marginal moisture, and increasing deep ascent will support convective development this evening and tonight, over and near southern NV, with MUCAPE generally in the 100-300 J/kg range. A residual, deep mixed layer from diurnal processes still should exist starting just above the surface, and locally strong gusts cannot be ruled out. Farther east, generally zonal flow aloft should cover most of the downstream areas in the central/eastern CONUS. A weakening, positively tilted shortwave trough is located over the southern Plains, and will continue to deamplify as it moves eastward across the Deep South overnight. While a rogue lightning strike still may occur in the associated precip plume near the central Gulf Coast, weak forcing and lack of greater instability should preclude 10% or greater unconditional thunderstorm coverage. ..Edwards/Gleason.. 01/22/2021
There’s more click here.