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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.

Wednesday, May 11, 2022

SPC May 11, 2022 2000 UTC Day 1 Convective Outlook

SPC 2000Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0259 PM CDT Wed May 11 2022 Valid 112000Z - 121200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM EASTERN SD ACROSS CENTRAL MN INTO WEST-CENTRAL WI... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE SOUTHERN HIGH PLAINS... ...SUMMARY... Severe thunderstorms are expected this afternoon/evening over the north-central states. Very large hail, wind, and a threat for tornadoes is expected. Additionally, widely scattered severe thunderstorms are anticipated across the southern High Plains. Wind/hail are the primary threats. ..Discussion... Only change this outlook update is to reduce probabilities over parts of eastern NE and IA to the latitudinal south of the MCV over the mid MO Valley. Otherwise, the forecast remains unchanged. ..Smith.. 05/11/2022 .PREV DISCUSSION... /ISSUED 1126 AM CDT Wed May 11 2022/ ...Synopsis... Expansive upper ridging currently extended from eastern Mexico through the Upper Great Lakes is expected to amplify throughout the day today. This amplification will occur as a shortwave trough embedded within the western CONUS mean troughing moves eastward towards the central Rockies and a large cyclone retrogrades westward/southwestward off the Atlantic Coast. Despite the presence of these large-scale features, the severe weather potential will be driven primarily by low-level and/or mesoscale features today, most prominently the convectively induced vorticity maximum moving northeastward out of KS. Severe thunderstorm development is anticipated as this vorticity maximum moves into the Mid MO Valley and Upper Midwest this afternoon and evening. Severe thunderstorms are also possible this afternoon and evening across the southern High Plains along the dryline and over the northern High Plains later this evening and overnight. ...Mid MO Valley into the Upper Midwest... A reservoir of 70 dewpoints is already in place from northeast KS/southeast NE across southern IA and into southern WI. Mid 60s dewpoints exist just north of this region. As the warm front lifts northward, expectation is for this low-level moisture to correspondingly advect northward/northwestward throughout the day. By the early afternoon, upper 60s dewpoints are expected to cover into southern MN and much of WI, with 70s dewpoints over eastern NE and much of IA. Steep mid-level lapse rates (sampled well by the 12Z OAX sounding) coupled with this abundant low-level moisture will result in a very unstable air mass downstream of the mesoscale convective vortex currently over KS. Strong heating will remove any convective inhibition and the expectation is for thunderstorm initiation across eastern NE early this afternoon as the leading edge of the MCV. An initially discrete mode is probable, with shear profiles supportive of supercells, even though some mid-level southeasterly flow around the MCV (as noted on the UEX VAD) does cast some uncertainty towards overall storm structure. Even so, strong buoyancy will support intense updrafts capable of large to very large hail and strong water loaded downbursts. Low-level flow is also sufficient for tornadogenesis, particularly if the southeasterly mid-level flow around the MCV turns more southerly with time. Upscale growth also appears probable after the initially discrete mode, with the orientation of the line perpendicular to the vertical shear vector. This results in the potential for some significant wind gusts over MN. ...Southern High Plains... Thunderstorms are expected to develop along the dryline this afternoon as the air mass destabilizes amid strong heating and modest low-level moisture. Mid to upper level flow will be rather modest, but enough directional shear should exist for some updraft organization. Higher dewpoints and buoyancy will exist across southern portions of the region, contributing to higher potential for all severe hazards, particularly very large hail. ...Southeast MT/Eastern WY into the Northern Plains... Large-scale ascent will increase this evening and overnight across the region, as the strong shortwave trough pivots out of the Great Basin and approaches. At the same time, associated mid-level moistening will help promote elevated thunderstorm development across southeast MT and eastern WY. Though buoyancy will be meager (MUCAPE generally 300-800 J/kg), favorable deep shear (effective-shear magnitudes around 50-65 kt) will favor supercell potential, with large hail as the primary threat. Read more CHECK UPDATE ZOOM GRAPHIC
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