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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.


Tuesday, September 7, 2021

SPC Sep 7, 2021 0600 UTC Day 2 Convective Outlook

SPC 0600Z Day 2 Outlook Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1240 AM CDT Tue Sep 07 2021 Valid 081200Z - 091200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE NORTHEAST AND MID-ATLANTIC... ...SUMMARY... Strong to severe thunderstorms are possible across parts of southern New England into the Mid-Atlantic vicinity Wednesday afternoon and evening. ...Northeast/Mid-Atlantic... An upper trough will spread eastward from the Great Lakes/Midwest to the Appalachians on Wednesday. A belt of moderate southwesterly deep-layer flow will overspread the Mid-Atlantic and Northeast corridor ahead of the trough. A surface cold front is forecast to extend from central OH southwestward to the lower MS Valley Wednesday morning. By the evening, the front is expected to extend across central NY into central VA/western NC, and from western ME to eastern NC by Thursday morning. Southerly low-level flow will transport 60s F surface dewpoints northward ahead of a cold front from the NC/VA Piedmont into southern New England. While cloudiness could limit heating somewhat across the pre-frontal warm sector, 500-1500 J/kg MLCAPE is forecast. The strongest destabilization is expected from eastern PA/NJ into VA/NC where better-quality boundary-layer moisture is expected. Large-scale forcing will remain relatively weak through peak heating, with stronger ascent remaining tied to the cold front. However, low-level convergence along a pre-frontal surface trough and weak shortwave impulses migrating over the region ahead of the main upper trough should be sufficient for at least isolated warm-sector storms. Effective shear magnitudes greater than 35 kt are expected over parts of the Northeast/Mid-Atlantic, becoming weaker with southward extent over VA/NC. This should support a few stronger cells capable of mainly strong/locally damaging gusts. Convection will increase in coverage near the front during the evening and some damaging-wind threat could accompany line segments developing near the boundary. However, deep-layer flow will become parallel to the front, resulting in training convection by evening. Additionally, increasing boundary-layer inhibition with the loss of daytime heating may further limit severe potential associated with the front during the evening/overnight period, and the eastward extent of severe potential across parts of New England remains a bit uncertain. ..Leitman.. 09/07/2021 Read more LIVE:
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CHICAGO UTC-6 during CST (Central Standard Time, e.g., winter)
CHICAGO UTC-5 during CDT (Daylight Savings Time, e.g., summer)