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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.

Saturday, June 19, 2021

SPC Jun 19, 2021 0730 UTC Day 3 Severe Thunderstorm Outlook

SPC 0730Z Day 3 Outlook Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0228 AM CDT Sat Jun 19 2021 Valid 211200Z - 221200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE NORTHEAST AND MID-ATLANTIC... ...SUMMARY... Isolated to scattered severe thunderstorms appear possible Monday from parts of the Northeast and Mid-Atlantic southwestward into the Ohio and Tennessee Valleys, lower Mississippi Valley, and southern Plains. ...Discussion... A large-scale upper trough should continue to amplify across much of the central/eastern CONUS on Monday. Enhanced west-southwesterly mid-level winds should accompany this upper trough, and they are forecast to gradually overspread the surface warm sector extending from the Northeast to the mid MS Valley and TN Valley vicinity by Monday evening. At the surface, the primary low associated with the upper trough is forecast to develop northeastward from the Great Lakes region into Ontario/Quebec through the day. A trailing cold front attendant to this low should move east-southeastward across much of the Northeast into the Mid-Atlantic, OH/TN Valleys, lower MS Valley, and southern Plains through Monday night. Current expectations are for storms to develop along a majority of the cold front by Monday afternoon. Rich low-level moisture is forecast to be present ahead of the front, and diurnal heating of this moist low-level airmass should foster the development of weak to moderate instability over much of the warm sector. The strongest mid-level flow may tend to lag the cold front slightly based on latest model guidance. But, there should still be enough deep-layer shear to support organized updrafts. The best forecast combination of instability and shear currently appears to extend across parts of the Northeast into the Mid-Atlantic in closer proximity to the surface low and upper trough. Convection will probably tend to become linear fairly quickly given the cold front serving as a forcing mechanism, and strong to damaging winds should be the main threat along/ahead of the front. The mid-level flow does weaken some with southward extent along the front, especially into the lower MS Valley and southern Plains. However, instability is forecast to be greater across these regions, which may help compensate to some extent for the modest deep-layer shear. Storms should eventually weaken Monday night along the length of the front as the boundary layer gradually stabilizes with the loss of daytime heating. ..Gleason.. 06/19/2021 Read more LIVE: