SPC 0730Z Day 3 Outlook
Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0205 AM CDT Sat Jul 31 2021 Valid 021200Z - 031200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... The probability of severe storms appears low across the USA on Monday. ...Synopsis... A deep upper low will move from Hudson Bay into western Quebec, with an expansive area of cyclonic flow aloft over eastern North America. Cool temperatures aloft with -10 C at 500 mb will extend as far south as northern AL/GA, though midlevel winds will be modest across the South. To the west, an upper high will shift a bit westward toward the Mojave Desert. At the surface, high pressure will stretch from the Rockies eastward across the Plains and into the Appalachians, with an east-west oriented front sagging south across TX and the Deep South. This front will provide a focus for nearly continuous thunderstorms throughout the period with 70s F dewpoints and ample instability ahead of the boundary. Elsewhere, cool midlevel temperatures will also exist west of the upper ridge across western WA and OR, aiding destabilization near a weak surface trough. ..TX into the Deep South... Storms are likely to be ongoing Monday morning from NM across northern and central TX and into the lower MS Valley. These storms are not expected to be severe as deep-layer shear remains below 30 kt and midlevel lapse rates will be poor. Pockets of heating are expected in between storm clusters, with increasing diurnal activity as the front/outflows progress slowly south. While localized, marginally severe gusts cannot be ruled out, predictability is currently low, and best addressed in later outlooks. ...OR... Destabilization is forecast near a surface trough during the afternoon over central OR, beneath weak upper ridging. Forecast soundings indicate an uncapped airmass by late afternoon, with steep lapse rates supporting at least 500 J/kg MUCAPE. Southerly midlevel winds around 30 kt combined with light (but veering with height) low-level winds may support a few cells capable of strong wind gusts or small hail, but the severe threat appears low at this time. ..Jewell.. 07/31/2021
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