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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.


Wednesday, July 20, 2022

SPC Jul 20, 2022 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 Wed Jul 20 2022 Valid 221200Z - 231200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE CENTRAL PLAINS INTO THE UPPER MIDWEST...AND THE MID-ATLANTIC INTO SOUTHERN NEW ENGLAND... ...SUMMARY... Isolated strong to severe thunderstorms may occur Friday from parts of the central Plains into the Upper Midwest, and from portions of the Mid-Atlantic into southern New England. ...Central Plains into the Upper Midwest... An elongated upper trough/low with multiple centers should remain over parts of central/eastern Canada on Friday. A belt of enhanced mid-level west-northwesterly flow is forecast to remain over much of the northern tier of the CONUS through the period. At the surface, a weak low should develop generally eastward over south-central Canada and ND through the day, with another area of low pressure potentially centered over SD. Rich low-level moisture should remain confined along/south of a weak front that is forecast to extend from parts of the central Plains northeastward into the Upper Midwest. Moderate to strong instability should develop across the warm sector with daytime heating, but a cap may inhibit thunderstorm development for much of the day. Still, some guidance suggests that isolated to scattered convection will develop from parts of NE into northern/central IA, southern MN, and WI by late Friday afternoon. This region will have only modest/nebulous large-scale ascent present aloft, but sufficient veering/strengthening of the wind profile with height through mid-levels should support convective organization with any thunderstorms that can develop along/near the front. Have included low severe probabilities for now given the uncertainty with overall thunderstorm coverage and placement, but the overall environment appears sufficient for multicells and perhaps a couple of supercells posing a threat for both isolated large hail and severe wind gusts. ...Mid-Atlantic into Southern New England... Mid-level heights are forecast to slowly rise across most of the Mid-Atlantic into New England on Friday. Even with generally subsident flow aloft, there is a signal in most guidance that convection may develop ahead of a secondary cold front as a weak mid-level perturbation traverses over these regions. Forecast instability and shear appear adequate for an isolated severe threat with any thunderstorms that can form. Have opted to include a Marginal Risk for parts of southern NY into northern PA/NJ and far southern New England where the best signal for robust convection exists. ..Gleason.. 07/20/2022 Read more CHECK UPDATE ZOOM GRAPHIC
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