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Archives for the SPC Convective Outlook are updated daily (approximately) with a live map at the beginning of each article. Follow the link at the end of the article to check for current updates on the NOAA/NWS Storm Prediction Center website. Also, see Archives for Chicago's hourly weather data on CARDINAL NEWS Magazine.


Friday, September 8, 2023

SPC Sep 8, 2023 0600 UTC Day 1 Convective Outlook

LIVE MAP (ABOVE) ... SPC 1200Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0103 AM CDT Fri Sep 08 2023 Valid 081200Z - 091200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM NORTHERN VIRGINIA INTO SOUTHWEST MAINE...AND FROM THE RED RIVER VALLEY ACROSS THE ARKLATEX AND SABINE VALLEY... ...SUMMARY... Thunderstorms producing both hail and damaging winds are possible from parts of the Mid Atlantic into the Northeast today, and from the Red River Valley and Arklatex southward across the Sabine Valley. Other isolated strong storms are expected over Montana. ...Synopsis... An upper ridge will remain over NM today, with anticyclonic flow aloft from CA into the northern Rockies and southeastward into the lower MS Valley. Meanwhile, a weak upper trough/low heights will remain over much of the East, resulting in cool profiles aloft. Various speed maxes will round the upper ridge, and possibly enhance thunderstorm potential. A low amplitude feature will affect MT with 30-40 kt westerly winds at 500 mb. To the southeast, relatively strong midlevel flow with around 50 kt will spread south out of the Ozarks and across AR, LA and northern MS. Meanwhile, modest 35 kt southwesterlies at 500 mb will remain over New England. At the surface, high pressure will extend from the upper Great Lakes southward across the middle and lower MS Valley, with weak northerly surface winds. A surface trough/wind shift will stretch from New England to the FL Panhandle, with 70s F dewpoints common ahead of it. Farther west, low pressure will exist over northwest TX and southwest OK with hot temperatures. Easterly winds over much of OK and eastern TX will maintain a narrow moist plume, east of the hot air and west of the surface ridge. A favorable area of instability and shear may thus develop due to the aforementioned enhanced flow aloft. ...Northeast and Mid Atlantic... A substantial plume of low-level moisture will remain over the region today, with models suggesting as much as 3000 J/kg MUCAPE from southeast NY across MA, southern VT, NH and southwest ME. Modest midlevel flow around 30 kt and front-parallel winds aloft should result in a corridor of enhanced thunderstorm probabilities, and water-loaded downdrafts may produce wind damage. In addition, the cool profiles aloft will favor brief periods of hail in the strongest storms. Farther south, another concentrated area of storms is likely from eastern WV across northern VA and into central MD, with storms moving northeastward across an unstable air mass. Although shear will be weak, forward-propagation is likely in the moist, uncapped air mass, with strong to severe winds expected through early evening. ...Southeast OK, Arklatex, eastern TX, LA... Storms are likely to be ongoing from eastern OK into western AR this morning, aided by weak theta-e advection at 850 mb with 25 kt westerlies. Cooling aloft will gradually occur throughout the period as a midlevel disturbance drops south out of MO. Some of this activity could contain marginal hail as temperatures aloft will be relatively cool with effective shear around 40 kt. As heating occurs downstream into LA, a narrow zone of 2500-3000 J/kg MUCAPE may develop, with a thunderstorm revival possible as the remnants of the early day activity proceeds southeastward. Damaging winds appear most likely, and storms may favor westward propagation as the low level lapse rates will be steeper to the west. Farther west, isolated storms are also expected near peak heating across the Red River Valley, and hot temperatures/deep mixing layers as well as steep midlevel lapse rates may favor damaging downbursts or even brief periods of marginal hail with the strongest storms. ...MT... Destabilization will occur during the afternoon due to strong heating, with mixed-layer CAPE around 500-1000 J/kg during the afternoon. As a midlevel short-wave trough moves eastward across the area, isolated to widely scattered thunderstorms are expected, over central MT, with peak convective coverage from late afternoon through mid evening. Given a belt of 30 to 40 kt mid-level westerlies and inverted-v type profiles, a few strong/longer-lived storms may produce locally damaging winds. Hail cannot be ruled out given cool temperatures aloft and 50 kt flow above 500 mb. ..Jewell/Squitieri.. 09/08/2023 Read more CHECK UPDATE ZOOM GRAPHIC
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