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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.

Sunday, June 20, 2021

SPC Jun 20, 2021 2000 UTC Day 1 Convective Outlook

SPC 2000Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0237 PM CDT Sun Jun 20 2021 Valid 202000Z - 211200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM PARTS OF EXTREME EASTERN IOWA ACROSS CHICAGOLAND TO NORTHWEST OHIO AND SOUTHERN LOWER MICHIGAN... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS SURROUNDING THE ENHANCED RISK...AND ALSO OVER PARTS OF GEORGIA AND THE CAROLINAS... ...SUMMARY... Scattered severe storms are expected across the Midwest into the lower Great Lakes/upper Ohio Valley. Large hail, severe/damaging winds, and a few tornadoes are possible. Damaging winds and a couple of tornadoes are also possible across the Southeast. ...20Z Update... ...Southeast Coast... Air mass downstream of Tropical Depression Claudette continues to destabilize amid modest heating and ample low-level moisture. As mentioned in MCD #1034, a couple of transient supercells may pose an isolated risk for a tornado or two through the afternoon. The highest conditional risk for a tornado appears to be over parts of eastern NC during the afternoon due to the larger hodographs. Additionally, based on recent trends and the location of center of TD Claudette, the severe risk across southeast GA has diminished enough to remove Slight Risk-equivalent probabilities. Isolated threat across southern GA/northern FL merits continued inclusion of 5% wind probabilities. ...Elsewhere... Forecast delineated outlined in the previous outlook (discussion below) remains valid and no changes are needed. ..Mosier.. 06/20/2021 .PREV DISCUSSION... /ISSUED 1122 AM CDT Sun Jun 20 2021/ ...MO to OH... Current water vapor loop shows a convectively augmented vort max over northern MO. New thunderstorm development has occurred in the past couple of hours in this region, with a corridor of rapid heating/destabilization occurring to the east from northeast MO into northern IL. Storms will likely intensify through the afternoon along this axis, with the risk of damaging winds, large hail, and isolated tornadoes. 12z CAM solutions differ on the handling of this cluster, but the potential appears to exist for a longer-lived bowing structure that would track all the way into northern OH this evening. Please refer to MCD #1032 for short-term details. ...MN/WI/IA/IL... Latest surface analysis shows a low over west-central MN. clearing skies ahead of the low, along with southerly low-level winds, will help to warm/moisten and destabilize this area by mid-afternoon. A consensus of model guidance shows intense thunderstorm development later today over southeast MN, southwest WI, and parts of northern/eastern IA. Large hail and damaging winds will be possible with these storms. A combination of remnant cloud debris and outflow boundaries complicate the scenario, but also increase the conditional risk of supercells and perhaps a few tornadoes this evening. If the storms over MO do not materialize into a longer-lived bow, then this area of storms may persist for several hours and track eastward across the ENH risk area. ...GA/SC/NC... The remnants of Claudette continue to affect parts of GA and the Carolinas today, with relatively strong low-level winds from southeast GA into southern SC. Considerable daytime heating and ample low level moisture will provide favorable thermodynamics for a few intense afternoon thunderstorms capable of damaging wind gusts and a few tornadoes. ...Southeast CO into southern KS late tonight... A surface cold front will extend from eastern CO into southern KS tonight, providing the focus for a few evening/overnight thunderstorms. Sufficient CAPE/shear along this zone will pose a risk of hail in the strongest storms. Read more LIVE: spc.noaa.gov