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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, May 30, 2022

SPC May 30, 2022 2000 UTC Day 1 Convective Outlook

SPC 2000Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0255 PM CDT Mon May 30 2022 Valid 302000Z - 311200Z ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS LATE THIS AFTERNOON AND EVENING ACROSS PARTS OF EASTERN SOUTH DAKOTA AND ADJACENT SOUTHWESTERN THROUGH NORTH CENTRAL MINNESOTA... ...SUMMARY... Numerous severe thunderstorms are forecast across parts of the Northern Plains and Upper Mississippi Valley, with more scattered to isolated activity southward into the central Plains today into tonight. Large to giant hail, 60-80 mph gusts, and a few long-tracked, intense tornadoes are possible. ...20Z Update... Adjustments to the 10 percent probability/categorical thunderstorm line across the Rockies into northern intermountain west vicinity have been made in an attempt to better account for where cloud cover/ precipitation and areas of stronger insolation are impacting boundary-layer destabilization. East of the Rockies, categorical and probabilistic lines have been adjusted to account for the progression of synoptic and subsynoptic features, primarily across the northern Great Plains. Farther south, across the central Great Plains into mid/lower Missouri Valley vicinity, severe probabilities have been adjusted westward a bit, closer to where the latest Rapid Refresh suggests that a southeastward advancing cold front will overtake a retreating dryline after 01-02Z. It appears that this forcing may account for the better potential for more substantive/widespread thunderstorm initiation (south of the northern Great Plains/upper Mississippi Valley vicinity), with large hail probably the primary potential severe hazard. ..Kerr.. 05/30/2022 .PREV DISCUSSION... /ISSUED 1125 AM CDT Mon May 30 2022/ ...A substantial threat for severe storms with all hazards is expected this afternoon/evening from eastern South Dakota into Minnesota... ...Eastern SD into MN though late evening... A midlevel shortwave trough and associated 70-90 kt midlevel jet will progress quickly north-northeastward from western KS/NE toward the upper MS Valley by tonight. An associated 992 mb surface low in central NE as of late morning will develop quickly north-northeastward across eastern SD to near the ND/MN border by early tonight. Scattered elevated storms, some with large hail, will likely persist through the day in the warm advection zone to the north of the warm front across eastern SD into southwestern MN. However, the warm sector with mid-upper 60s dewpoints now across eastern NE/western IA will spread northward during the day, with increasing potential for surface-based storm development near and just ahead of the surface cyclone and ejecting midlevel trough by midday/early afternoon. It appears the convection will begin as clusters by midday across east/southeast SD, and expand quickly northeastward into central/northern MN by late afternoon/evening. All hazards can be expected with the surface-based storms during the afternoon, in an environment favorable for fast-moving supercells. However, there are some concerns about mixed convective mode/bowing segments given potential storm interactions and strong forcing for ascent. Deep-layer vertical shear will be quite strong (effective shear in excess of 65 kt), with long hodographs and low-level, clockwise curvature (effective SRH of 300-400 m2/s2). These wind profiles, in combination with midlevel lapse rates greater than 8 C/km and MLCAPE of 2000-3000 J/kg, will support the threat for a few long-tracked, intense tornadoes and very large hail with any semi-discrete supercells. As previously mentioned, there will also be some potential for storm interactions and upscale growth into line segments capable of producing significant outflow gusts up to 80 mph, given the very strong environmental wind profiles. ...IA/NE to KS/northern OK later this afternoon into tonight... The larger height falls and stronger forcing for ascent will spread northward toward eastern SD/MN through the afternoon/evening, but the warmest portion of the elevated mixed layer will be east of the dryline by late afternoon. Forcing for ascent will be focused in the low levels from the dryline/cold front intersection southward along the dryline, and isolated storm development may occur by late afternoon/evening. Lapse rates aloft will not be ideal, given fairly warm temperatures near 500 mb on the anticyclonic side of the jet. Still, the storm environment conditionally favors supercells with all hazards, given sustained storm development. Otherwise, despite height rises overnight, the threat for convection with occasional large hail/damaging winds will persist (especially toward northeast KS) as the cold front overtakes the remnant dryline, and with warm advection on the nose of a 50+ kt low-level jet. ...FL/south GA this afternoon... Scattered sea breeze storms are expected this afternoon, skewed to the western half of the FL Peninsula given low-level easterly flow. Strong surface heating and moderate buoyancy could support isolated wind damage with downbursts, as well as some hail. Read more CHECK UPDATE ZOOM GRAPHIC