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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.

Saturday, July 31, 2021

SPC Jul 31, 2021 0600 UTC Day 2 Convective Outlook

SPC 0600Z Day 2 Outlook Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1248 AM CDT Sat Jul 31 2021 Valid 011200Z - 021200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER EASTERN NORTH CAROLINA AND SOUTHEAST VIRGINIA... ...SUMMARY... Several severe storms will be possible Sunday over eastern North Carolina and southeast Virginia. Isolated severe storms will be possible over parts of Pennsylvania and New York. ...Synopsis... Cyclonic flow aloft will persist over the Great Lakes and Northeast, with an upper speed max moving across the OH Valley and into the Northeast. This feature will provide large-scale lift as well as increasing deep-layer shear. Meanwhile, a leading speed max will move off the East Coast with the right-entrance region of the upper jet sweeping across the Mid Atlantic. At the surface, a steadily deepening low will move across Lake Erie and Ontario during the day, with a lee trough over eastern VA and NC. A cold front will extend southwestward from the Mid Atlantic across the Deep South and into northern TX, with ample moisture and MUCAPE to 3000 J/kg ahead of the front. Weaker instability is expected near the northern low and cold front in the 500-1000 J/kg MUCAPE range as dewpoints only average 55-60 F. This front is forecast to move into western and central NY and PA prior to 00Z. Elsewhere, an upper high will be centered over the Four Corners states with ridge extending north into Alberta, with scattered daytime storms over the West. ...Mid Atlantic... Rain and thunderstorms may be ongoing across parts of eastern VA into the Delmarva Sunday morning, in a region of low-level warm/moist advection. Behind this activity, dewpoints are expected to rise into the lower 70s F into VA, with mid to upper 70s F over the eastern Carolinas. A plume of steep lapse rates will develop across the Carolinas, with MUCAPE over 3000 J/kg expected. While low-level winds will be relatively weak, they will veer with height, becoming westerly at around 40 kt in the midlevels. This should create hodographs favorable for a supercell or two, although storm interference appears likely given CAM trends. Effective SRH over 100 m2/s2 is expected. Diurnal storms are expected to form between 18-21Z over central NC, with upscale growth possible as they progress east. Damaging winds appear likely, along with marginal hail and perhaps a tornado. Less storm coverage is anticipated farther south into SC, but robust instability may favor a few damaging gusts there. ...NY and PA... Storms will initially develop over southwest Ontario, and are likely to cross into the USA after 18Z, from northeast OH into western NY. Heating ahead of this frontal activity should allow for a steady ramp up of low-topped convection, with damaging gusts the primary concern as cells merge along the front. Marginal hail may occur before storm mode becomes linear. Weak instability and low-level winds suggest any gusts over 50 kt will be isolated. ..Jewell.. 07/31/2021 Read more LIVE: spc.noaa.gov