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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, August 1, 2021

SPC Aug 1, 2021 0600 UTC Day 1 Convective Outlook

SPC 1200Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1257 AM CDT Sun Aug 01 2021 Valid 011200Z - 021200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM SOUTHEAST VIRGINIA THROUGH EASTERN NORTH CAROLINA... ...SUMMARY... Strong to severe storms with damaging wind and perhaps a tornado may impact southern portions of the Mid Atlantic today. A few strong to severe storms are also possible over the Northeast and the Gulf Coast States. ...Middle Atlantic area... The synoptic eastern U.S. upper trough will amplify further today as a strong, embedded shortwave trough moves southeast into the Great Lakes. An impulse currently moving through the southern Appalachians will continue through southern VA and northeastern NC during the early morning hours. Thunderstorms are expected to develop early in the period from southeast VA into northeast NC. This will occur as stronger forcing for ascent attending the impulse interacts with the moderately unstable environment along and south of a front that will be situated from southeast VA southwestward through NC. While these storms may be slightly elevated, a belt of stronger (40-45 kt) mid-level winds within the base of the upper trough will contribute to 40+ kt effective bulk shear, and some of the storms may evolve into supercells and bowing segments with a threat for mainly damaging wind and perhaps a tornado or two. Additional storms are expected farther south along the boundary across eastern NC as the atmosphere destabilizes through the morning, and this activity will pose threat for damaging wind as they spread east toward the coast. ...Northeast States... A strong shortwave trough currently moving southeast through the upper Great Lakes will continue through the Northeast States during the day. Low-level moisture in this region will be somewhat limited with mid to upper 50s F dewpoints. This along with weak mid-level lapse rates will limit MLCAPE to 500-1000 J/kg as the boundary layer warms during the afternoon. An increase in winds will occur mainly near and above 500 mb resulting in 35-40 kt effective bulk shear. However, flow in the near-surface to 700 mb layer is forecast to remain relatively weak. Storms are expected to develop along the front and spread east through NY and PA during the late morning into the afternoon. Most CAMS indicate upscale linear growth, and this seems reasonable given degree of forcing. Primary threat will be damaging wind, especially as the boundary layer destabilizes during the afternoon from central and eastern PA and NY. Given the expected marginal thermodynamic environment, will maintain MRGL category this outlook, but an upgrade to SLGT will be considered in later updates. ..Dial/Moore.. 08/01/2021 Read more LIVE: spc.noaa.gov