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Weather conditions on bar directly above are near Lakefront. Tabs under Moon Phases refer to O'Hare (official).

Archives for SPC Convective outlook are updated daily with a live map a the beginning of the article. Touch or click map to get possible update, and follow link at end of article for referral to NOAA/NWS Storm Prediction Center. Archives for Chicago's hourly weather data were updated 24-48 hours after end of each day prior to Dec. 2020.

Wednesday, April 6, 2022

SPC Apr 6, 2022 2000 UTC Day 1 Convective Outlook

SPC 2000Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0256 PM CDT Wed Apr 06 2022 Valid 062000Z - 071200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE SOUTHEAST AND SOUTHERN APPALACHIANS VICINITY... ...SUMMARY... Severe thunderstorms capable of producing swaths of damaging gusts, large hail, and a few tornadoes are expected across the Southeast States and near the southern Appalachians late this afternoon into this evening. ...20Z Update... The Marginal Risk and associated hazard probabilities have been trimmed from the west based on the progression of the cold front, but otherwise no major changes have been made to the outlook. The scenario remains complex, with thunderstorms gradually increasing in coverage and intensity across parts of GA within a weak warm advection regime, as well as across parts of AL along the cold front and separately along a prefrontal trough. Additional thunderstorm development is expected later this afternoon into the early evening into parts of northeast AL, northwest GA, middle/eastern TN, and eastern KY along the cold front. Hail, damaging winds, and a few tornadoes will be possible with the strongest storms across the region. See MCD 425 for additional information regarding the short-term severe threat in GA, and the previous outlook discussion below for more information regarding other areas. ..Dean.. 04/06/2022 .PREV DISCUSSION... /ISSUED 1112 AM CDT Wed Apr 06 2022/ ...Southeast/Southern Appalachians ... A complex scenario is expected to evolve today across the Southeast states, with multiple instigators in place for convective initiation. Recent surface analysis places a remnant outflow boundary from about 15 miles north of AUO in east-central AL east-northeastward across central GA to AGS. Some deeper cumulus and a few lightning flashes have been noted along this boundary over the past hour amid persistent southwesterly flow and limited low-level moisture convergence. A second feature is the approaching cold front, which currently extends from western TN back southwestward into far southern AR. A well-defined gravity wave precedes this front, with the leading edge of this wave currently extended from middle TN southwestward through far northwest AL and central MS. Lastly, a compact shortwave trough just off the LA coast is readily apparent in recent water vapor imagery. All of these features will result in the potential for complex convective evolution within the moist and buoyant air mass over the Southeast today. Current expectation is for initial development across central AL along and ahead of the gravity wave this afternoon. Additional development appears possible within the warm sector across central GA as well, particularly later into the afternoon as the gravity wave approaches. Furthermore, in situ initiation is also possible along the outflow boundary. All this development appears likely to occur around the same time this afternoon, with more of a linear mode favored on the gravity wave and more cellular development ahead of it. Thereafter, the outflow could then act as a corridor for further storm intensification/organization as all of these thunderstorms move eastward/northeastward. All severe hazards are possible with this evolution. Relatively dry mid-levels will contribute to an outflow-dominant storm structure within most of the cellular development. Steep mid-level lapse rates will promote hail in any robust updrafts. Veering low-level flow with height, while not overly strong, is strong enough to support the potential for QLCS tornadoes. Farther north (from middle TN into the southern Appalachians), initiation appears more probable along the cold front itself, and not the preceding gravity wave. Clearing is already occurring across parts of middle TN and the expectation is for moderate buoyancy to develop ahead of the front, with initial scattered development across middle TN before becoming more widespread over eastern TN and adjacent parts of northeast AL/northwest GA and eastern KY. As with areas south, all severe hazards are possible. Given the strong mid-level flow, hail is expected to be a risk throughout the afternoon and evening. Damaging wind gusts are possible within any bowing segments and a tornado or two may also occur, particularly if a robust updraft can mature ahead of main line of storms. Read more CHECK UPDATE ZOOM GRAPHIC