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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.

Friday, July 30, 2021

SPC Jul 30, 2021 0600 UTC Day 2 Convective Outlook

SPC 0600Z Day 2 Outlook Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1243 AM CDT Fri Jul 30 2021 Valid 311200Z - 011200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM EASTERN KANSAS ACROSS MISSOURI AND INTO WESTERN KENTUCKY...AND CENTERED OVER WISCONSIN... ...SUMMARY... Marginally severe thunderstorms will be possible Saturday centered over Missouri and Wisconsin. ...Synopsis... A broad region of cyclonic flow aloft will remain over the northeastern quarter of the CONUS, with various embedded waves. One wave will move across the mid MS Valley during the day and east/southeastward into the OH Valley by 00Z. Meanwhile, a weak surface low will move from eastern KS into southern MO, with a cold front moving south across KS and MO. Eastern portions of the front will become stationary, or perhaps a slow-moving warm front into the lower OH Valley. To the north, heights will fall across the upper MS Valley and Great Lakes as a midlevel jet noses southward across the Arrowhead of MN and into WI overnight. A weak surface trough will be present, along with sufficient moisture to support storms after 21Z from the MN/WI border toward Lake MI. Elsewhere, an upper ridge will extend from the Four Corners northwestward into British Columbia, with scattered daytime storms beneath. ...MO and Vicinity... Scattered storms, possibly an MCS, are likely to be ongoing anywhere from IA into northern MO, and perhaps western IL Saturday morning, aided by warm/moist advection with 30+ kt west/southwest 850 mb winds. While potential outflow may push south across MO during the day, a slow-moving warm front may develop east of any ongoing activity toward the OH Valley. Depending on initial storm coverage and intensity, some of the early activity may persist during the day, with mainly gust potential. Otherwise, an unstable air mass will develop south of the front/outflow boundary, with heating and 70s F dewpoints resulting in tall CAPE profiles and MLCAPE at or above 3000 J/kg. West/southwest low-level winds will favor redevelopment, but degree of organization is uncertain and will depend on the early day activity. Given the strong MLCAPE, a few cores may produce marginal hail, although deep-layer shear will not be very strong. Low-level shear may prove sufficient for mesocyclones from southeast MO into the lower OH Valley, conditional on storm mode. ...WI and Vicinity... Lapse rates will steepen throughout the day with weak surface convergence and low 60s F dewpoints. MLCAPE up to 1000 J/kg may develop, beneath northwest flow aloft. Scattered storms are forecast after 21Z from eastern MN across WI and into Lower MI, with around 40 kt deep-layer shear. This may favor cellular storm mode capable of marginal hail or wind gusts. Activity will likely dwindle between 03Z-06Z as the air mass stabilizes and northwest winds bring in drier air. ..Jewell.. 07/30/2021 Read more LIVE: spc.noaa.gov