SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1214 AM CDT Thu Oct 15 2020 Valid 151200Z - 161200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Minimal thunderstorm activity is forecast across the contiguous United States on Thursday. ...Discussion... Large-scale heights are expected to fall across the mid-MS/OH Valley region as upper troughing progresses into this region during the latter half of the period. Another reinforcing continental air mass will overspread much of the CONUS as a cold front settles southeast through the period. This will effectively shunt higher-PW air mass into the low latitudes, primarily across the coastal Plain of TX and over the southern Gulf basin/south FL. As much of the country gradually dries/stabilizes, deep convection will become less likely. A few areas where isolated thunderstorms may develop are, 1) TX-LA region, 2) Southeast, and 3) northern Plains. TX/LA -- Surface front will surge south across TX during the day as the primary short-wave trough digs toward the OH Valley. Although low-level convergence will prove minimal along this boundary, surface heating across deep south TX suggests parcels will be most buoyant across this region. Isolated thunderstorms may develop along/post frontal as the wind shift moves into this region. Southeast -- surface anticyclone will shift off the Atlantic coast during the day which will allow more favorable low-level trajectories and convergence to focus from the FL Peninsula into the Carolinas. While forecast lapse rates are poor, models suggest scattered convection will evolve along this favorable zone of low-level convergence. Northern Plains -- steep low-level lapse rates will develop across the northern Plains later today as strong surface heating north of the primary jet enhances instability. While moisture is quite low across this region, forecast soundings suggest scattered weak convection is possible. The strongest updrafts may produce a few lightning flashes. ..Darrow/Moore.. 10/15/2020
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