SPC 1630Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1130 AM CDT Sun Sep 05 2021 Valid 051630Z - 061200Z ...NO SEVERE THUNDERSTORM AREAS FORECAST... ...SUMMARY... Organized severe thunderstorms are not expected through tonight, although very isolated strong wind gusts will be possible across portions of the northeast U.S., Arklatex region, upper Great Lakes and southeast Arizona. ...Synopsis... A cold front, extending from Lake Ontario southwest to the Arklatex and southwest Texas, will move steadily east across its northern extent through tonight as a large-scale upper trough moves east across the Great Lakes. From the Arklatex into TX, the front will move only slowly southward today. Upper-level high pressure will remain over the southwest states, with broadly cyclonic mid-level flow from the central Plains to the northeast U.S. ...Northeast... Stronger low- and mid-level wind fields, contributing to effective shear values of 40-50 kts, will be confined to the northeast U.S. this afternoon. Substantial cloud cover will limit diurnal heating, and poor lapse rates will combine to result in only modest destabilization ahead of the front. Although an isolated stronger storm may pose a risk for strong gusts, expected coverage remains too low for introduction of severe wind probabilities with this outlook. ...Lower MS Valley west into central TX... Weaker flow and resultant deep-layer shear will prevail across the lower MS Valley west into the TX portion of the front (at or below 25 kts), although stronger diurnal heating of a moist air mass (lower 70s surface dew points) will result in greater instability (MLCAPE averaging 2000-3000 J/kg). Scattered thunderstorm development is anticipated this afternoon along the front, and an isolated more intense storm will be capable of strong wind gusts. ...Great Lakes... A pronounced shortwave trough will move southeast across Lake Superior/MI Upper Peninsula and portions of lower MI this evening. Strong ascent/mid-level cooling with this trough will contribute to weak instability, and strengthening wind fields could result in gusty winds developing with a couple stronger showers/thunderstorms. ...Southeast AZ... An increase in thunderstorm coverage is expected today aided by ascent with a midlevel disturbance pivoting south across southern AZ/NM, and some potential will exist for a stronger wind gust given notable DCAPE on RAP forecast soundings. Weak mid-level flow should limit the extent of any severe potential with the risk remaining localized and too low for severe probabilities. ..Bunting/Jirak.. 09/05/2021 Read more LIVE: spc.noaa.gov
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