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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, August 13, 2021

SPC Aug 13, 2021 1630 UTC Day 1 Convective Outlook

SPC 1630Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1050 AM CDT Fri Aug 13 2021 Valid 131630Z - 141200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF THE OHIO VALLEY...MID-ATLANTIC REGION...AND A SMALL PART OF THE CENTRAL HIGH PLAINS... ...SUMMARY... Strong to severe thunderstorms are most probable this afternoon and evening over portions of the Ohio Valley, Mid-Atlantic region, and a small part of the central High Plains and nearby foothills. ...Ohio Valley... A low-amplitude upper trough is present today over the Great Lakes region, with the southern fringe of stronger westerlies as far south as the mid-Mississippi and Ohio Valleys into the northeast states. A surface baroclinic zone extends from Lower MI into MO/IL then westward into OK. This boundary and the hot/humid air mass to the south will be the focus for scattered afternoon thunderstorms, with the potential for locally gusty or severe wind gusts. Model guidance is very diverse in the forecasts of convective clusters that might result in a more focused risk of severe storms later today. However, given the reservoir of high CAPE in the ongoing SLGT risk area from KY into PA, will not make any changes at this time. ...Mid Atlantic Region... Scattered thunderstorms are expected to develop this afternoon along the Blue Ridge of western VA and track slowly eastward through the afternoon. Vertical shear is weak and convective organization should be limited. However, a moist and very unstable air mass may result in locally damaging wind gusts for a few hours across the region. ...CO/WY... Southeasterly upslope low-level winds are in place today over northeast CO and southeast WY. This should help to initiate isolated thunderstorms off the Laramie Range of WY and northern foothills of CO. Favorable CAPE/shear parameters for a conditional risk of hail and damaging wind gusts in those storms that form, but 12z model guidance suggests convective coverage will be quite sparse. It is also unclear if storms will be able to maintain intensity as they move off the higher terrain. Have adjusted the risk areas to be more focused westward given the uncertainties. ...AZ... Strong heating and dewpoints in the 50s/lower 60s over the mountains of eastern AZ will lead to scattered afternoon thunderstorms. Weak northeasterly mid level winds will help to propagate these storms westward off the higher terrain. Any of these storms will pose a risk of gusty/damaging wind gusts as they move into the higher CAPE/heat of the lower deserts. An upgrade to SLGT risk may be warranted later today if confidence grows in this scenario. ..Hart/Moore.. 08/13/2021 Read more LIVE: spc.noaa.gov