SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0650 AM CST Tue Jan 05 2021 Valid 051300Z - 061200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Isolated thunderstorms may affect portions of the Carolinas today. ...Synopsis... In mid/upper levels, a progressive and fairly amplified pattern will continue, atop a generally dry and/or stable boundary layer. This pattern will keep rich theta-e shunted to lower latitudes and well out over the Atlantic, precluding deep moist convection over the bulk of the CONUS, with one possible exception noted below. A well-defined trough, arcing from ID south-southeastward across northern AZ to northern Baja -- will shift eastward to the Great Plains and southern Rockies by the end of the period, with a basal shortwave/vorticity max digging across NM around 12Z tomorrow. In response, low-level pressure/height falls and related warm/moist advection, will increase over the southern Plains through tonight, but with insufficient moisture and lift for thunder until after the period. ...SC... Isolated thunder may accompany convection mainly across parts of northern SC this afternoon. A long, negatively tilted, mid/upper trough is apparent in moisture-channel imagery from Lakes Superior/ Michigan across eastern portions of KY/TN to southeastern GA. The primary vorticity lobe now near CHA will shift east-southeastward across SC today, beneath the left-exit region of a cyclonically curved, 250-300-mb jet streak. Associated large-scale ascent/ cooling in midlevels will steepen lapse rates enough to support showers and isolated thunderstorms, with surface-based effective- inflow parcels and minimal MLCINH possible by early/mid afternoon. Forecast soundings suggest equilibrium levels (EL) under the 500-mb level but aloft of the -20 deg C isotherm, with surface-EL lapse rates 6.5-7 deg C/km, and marginal but sufficient near-surface moisture for around 50-200 J/kg MLCAPE. Thunderstorm depth and coverage should be greater offshore when the colder air aloft moves over the Gulf Stream this afternoon and evening. ..Edwards.. 01/05/2021
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