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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.

Monday, August 30, 2021

SPC Aug 30, 2021 0600 UTC Day 1 Convective Outlook

SPC 1200Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1239 AM CDT Mon Aug 30 2021 Valid 301200Z - 311200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE GULF COAST AND OVER THE NORTHERN AND CENTRAL PLAINS... ...SUMMARY... Some tornado threat continues across the central Gulf States with remnants of Ida. Severe storms are also possible across parts of the northern and central Plains. ...Ida... Ida continues its slow northward advance across southeast LA this morning. Remnants will gradually curve northeast across northern MS by the end of the day1. Latest model guidance suggests strong low-level shear will remain confined to the eastern semicircle and there is reason to believe some boundary-layer heating will contribute to buoyancy from southern LA to the FL Panhandle. Have expanded higher tornado probabilities across the FL Panhandle where surface temperatures may warm to near 80F. Forecast thermodynamic profiles would yield at least 2500 J/kg MLCAPE with these temperatures and more robust updrafts can be expected. ...Northern/Central Plains... Broad upper ridging is forecast to continue across the southwestern US today as more significant troughing settles into the Pacific Northwest. Modest westerly flow will extend into the northern Great Basin-WY before turning more northwesterly across the Plains. Early-morning water-vapor imagery suggests a few weak disturbances are translating within this flow regime toward the northern/central High Plains. While appreciable height changes are not forecast across the Plains, one of these features is expected to aid thunderstorm development by late afternoon across the western Dakotas. Strong boundary-layer heating will aid destabilization such that parcels should be free to convect by 22-23z. Forecast sounding at BPP in southwest ND yields 2600 J/kg MLCAPE by this time with a surface temp/dew point of 83/59F. Surface-6km bulk shear is adequate for supercells, especially given the veering winds with height. Latest HREF guidance is not particularly helpful with most members struggling with a consistent signal. For this reason, will give more credence to boundary-layer heating which should prove instrumental in initiation. Isolated storms may also develop south across western NE where strong heating is expected. LLJ is forecast to increase during the evening and this should encourage longevity/expansion of thunderstorms after sunset. Downstream, there is some concern that convection may develop along the boundary draped across southeast NE where weak warm advection will be noted. Weak inhibition and the presence of the boundary suggest some potential for afternoon convection. However, stronger low-level convergence and more focused LLJ to the west suggest an upward-evolving complex will likely move into this region late. Have expanded the SLGT Risk to account for some uncertainty across this region. Large hail and damaging winds should be the primary threats with this activity. ...New England... Models continue to suggest a few robust storms are possible later today in association with approaching short-wave trough. Surface heating is not expected to be particularly strong and weak buoyancy should limit intensity with most storms. Even so, a few gusty winds could accompany the stronger cells. ..Darrow/Wendt.. 08/30/2021 Read more LIVE: spc.noaa.gov