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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.


Monday, September 27, 2021

SPC Sep 27, 2021 2000 UTC Day 1 Convective Outlook

SPC 2000Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0241 PM CDT Mon Sep 27 2021 Valid 272000Z - 281200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON/EVENING ACROSS SOUTHWEST TX...AND LATE TONIGHT FROM EASTERN OH INTO WESTERN PA... ...SUMMARY... Marginally severe hail and wind gusts may occur late this afternoon/evening across southwest Texas, and isolated large hail may occur late tonight from eastern Ohio into western Pennsylvania. No changes necessary to the ongoing forecast. Further details below. ..Wendt/Gleason.. 09/27/2021 .PREV DISCUSSION... /ISSUED 1124 AM CDT Mon Sep 27 2021/ ...Eastern OH into western PA late tonight... Downstream from midlevel height rises over the northern Plains, a trough will amplify some by tonight over the lower Great Lakes. At the surface, a cold front will move slowly south-southeastward across Lower MI/lower Great Lakes/NY by tonight. Though the maritime tropical air mass is confined to the Gulf coast after a prior frontal intrusion, a gradual increase in low-level moisture is expected in advance of the cold front from the OH Valley into PA. The moistening will occur in tandem with the eastward advection of a plume of steep midlevel lapse rates (at or above 8 C/km), which will contribute to MUCAPE of 1000-1500 J/kg rooted close to 850 mb overnight. Moistening and ascent could become sufficient for elevated thunderstorm development after 06z tonight from eastern OH into PA, where the moderate buoyancy/steep midlevel lapse rates may support isolated large hail from 06-12z. ...Southwest TX this afternoon/evening... An embedded shortwave trough is ejecting northeastward over west central TX as of late morning, around the eastern periphery of a midlevel low over western NM. In the wake of this low-amplitude trough, surface heating and boundary-layer dewpoints near 60 F will result in moderate buoyancy this afternoon across southwest TX. Isolated storms may form by mid-late afternoon in association with terrain circulations to the south-west of Fort Stockton. Relatively straight hodographs and effective bulk shear near 35 kt, with MLCAPE of 1000-1500 J/kg, suggest that a splitting supercell is possible, with strong outflow winds and/or marginally severe hail. Read more LIVE:
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