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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 7, 2021

SPC Jul 7, 2021 2000 UTC Day 1 Convective Outlook

SPC 2000Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0258 PM CDT Wed Jul 07 2021 Valid 072000Z - 081200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE SOUTH ATLANTIC COAST...SOUTHERN GREAT LAKES TO SOUTHERN NEW ENGLAND...MONTANA...BLACK HILLS... ...SUMMARY... A few brief tornadoes will remain possible through tonight, in association with Tropical Storm Elsa along the South Atlantic Coast. Scattered damaging winds are possible into this evening from the southern Great Lakes to southern New England. Scattered severe wind gusts and large hail are possible across Montana. A conditional threat for very large hail also exists near the Black Hills. ...Black Hills into eastern WY... The Marginal and Slight Risks have been expanded slightly westward across portions of eastern WY and southward across portions of the NE Panhandle, to account for the possibility of a supercell or two emerging out of a building cumulus field across Converse and Campbell counties. Otherwise, the forecast remains on track in this region, with a conditional risk of very large hail and locally damaging wind with any supercell that can form late this afternoon or early evening. ...Western NY... The Slight Risk has been expanded slightly northward across western NY, since it appears that convection may spread northeastward out of western PA and pose a threat for locally damaging wind later this afternoon into the early evening. ...Elsewhere... Aside from the adjustments mentioned above, no substantial changes have been made to the outlook. See the previous discussion below for more information. ..Dean.. 07/07/2021 .PREV DISCUSSION... /ISSUED 1136 AM CDT Wed Jul 07 2021/ ...Northern Florida and southeast Georgia/coastal South Carolina... Tropical Storm Elsa will continue to move northeast across north Florida into South Carolina by early Thursday; reference NHC for the latest forecast and track details. The potential for brief tornadoes will remain focused in the northeast quadrant of the cyclone across far north Florida and southeast Georgia this afternoon. As Elsa becomes more progressive later today into tonight, the tornado potential is expected to develop into South Carolina this evening, aided by very rich moisture near the South Atlantic Coast. ...Southern Great Lakes to southern New England... Despite generally modest mid-level lapse rates, robust boundary-layer heating and rich low-level moisture near/south of a west/east-oriented front will support a broad plume of moderate buoyancy with MLCAPE reaching 1500-2500 from Indiana/southern Lower Michigan to the Delaware and Hudson Valleys. The belt of stronger 700-mb westerlies will largely remain confined to Lower Michigan across New York and New England. Scattered thunderstorms are expected to develop this afternoon near and south of this belt of stronger flow. While sporadic damaging winds from microbursts should dominate, a few multicell clusters could develop within this regime and produce scattered damaging winds from southern New England to the Lower Great Lakes through early/mid-evening. ...Montana... A shortwave trough along the Pacific Northwest coast will shift to the Rockies along the international border through tonight as it impinges on the mid-level ridge. A belt of enhanced mid-level westerlies will accompany this wave and spread east into Montana by tonight. Initial afternoon thunderstorm development is expected in the weak buoyancy environment across western Montana. This activity will eventually impinge on a residual plume of moderate buoyancy over eastern Montana and should sustain an organized severe threat through at least this evening. The greatest risk for large hail should be focused across central Montana where semi-discrete supercells are possible. But the overall threat will likely be from severe wind gusts given the initial high-based development and steep low to mid-level lapse rates supporting cold pool generation. Significant severe wind gusts are possible if an organized eastward-moving cluster can become established prior to a more substantial increase in nocturnal MLCIN. The severe threat will wane overnight as activity spreads east of the buoyancy plume in the Dakotas. ...Black Hills vicinity... A couple of discrete supercells may develop within a weak low-level upslope flow regime over the Black Hills or along the lee trough in far eastern Wyoming. Effective shear of 35-50 kt would support a few supercells capable of very large hail with any supercell late this afternoon into early evening. ...Lower/middle Texas coast... Various guidance imply that low-level winds may modestly strengthen this afternoon in vicinity of a low along the lower Texas coast. While the degree of inland destabilization is uncertain, at least a few weak/transient supercells could occur near the coast through tonight, which could account for a waterspout or brief tornado potential. ...Southeast Arizona... It appears that east-northeasterly mid-level winds will increase across the region on the southern periphery of the upper ridge centered over the southern Great Basin. While the coverage of storms is a bit uncertain, there is some potential that a few storms that develop over the mountains this afternoon could spread southwestward toward the lower elevations of southeast Arizona. While thunderstorm-related strong wind gusts are plausible, the overall marginality of the scenario precludes an introduction of severe probabilities at this time. Read more LIVE:
SUNRISE AND SUNSET TIMES IN UTC (if you're not logged in to Google)
CHICAGO UTC-6 during CST (Central Standard Time, e.g., winter)
CHICAGO UTC-5 during CDT (Daylight Savings Time, e.g., summer)