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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, June 11, 2022

SPC Jun 11, 2022 2000 UTC Day 1 Convective Outlook

SPC 2000Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0254 PM CDT Sat Jun 11 2022 Valid 112000Z - 121200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS THE QUAD-STATE AREA OF SOUTHEASTERN NEBRASKA/SOUTHWESTERN IOWA/NORTHEASTERN KANSAS/NORTHWESTERN MISSOURI... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM SOUTHEASTERN MONTANA EAST-SOUTHEASTWARD INTO CENTRAL SOUTH DAKOTA... ...SUMMARY... A few clusters of strong to severe thunderstorms are expected to develop from the northern Rockies into the middle and lower Missouri Valley this afternoon and tonight. Damaging winds and hail will be most likely. An isolated tornado is possible over the middle Missouri Valley and vicinity. ...Discussion... Few substantive changes are being implemented to the outlook in this update, as prior reasoning continues to adequately reflect expectations regarding convective evolution/severe risk this afternoon and tonight. The primary adjustment to the areal risk depiction is being made over the eastern Missouri vicinity, where an eastward expansion in both SLGT and MRGL risk areas is being included. Continued heating/destabilization is forecast across this area, which may support southeastward-moving storms emanating from Iowa to affect areas as far east as the Mississippi Valley this evening. Otherwise, the existing outlook remains aligned with current thinking. ..Goss.. 06/11/2022 .PREV DISCUSSION... /ISSUED 1125 AM CDT Sat Jun 11 2022/ ...IA/NE/MO/KS... Have upgraded portions of the Slight Risk area to Enhanced (Level 3 of 5) Risk with this outlook based on increasing confidence in a corridor of severe hail (possibly significant) and wind developing late this afternoon/early evening and moving south tonight. Daytime heating of a very moist (upper 60s/lower 70s surface dew points) air mass will contribute to strong instability across the region by afternoon with MLCAPE values at or above 3000 J/kg from southeast NE south across eastern KS/western MO. Combined with strong mid/upper-level northwest flow on the periphery of an expansive southwest U.S. upper high, a very favorable environment for supercells should be in place by late afternoon. Expect initiation by late afternoon or early evening across eastern NE/western IA in the vicinity of a southward-moving surface boundary, with storms moving generally south tonight. Forecast soundings support a risk for very large hail during the first few hours after initiation, with damaging winds becoming increasingly likely as storms develop into a cluster/bowing mode with time. Some tornado risk will exist given forecast curved low-level hodograph structure, especially across the Enhanced Risk area. ...MT/SD... Strong westerly flow aloft will reside across the northern Plains as a weak cold front moves slowly south across MT. Pockets of daytime heating will result in afternoon temperatures in the 80s from southern MT into SD, with dewpoints averaging in the upper 40s and 50s. 12z guidance is in agreement that scattered thunderstorms will form over the mountains of western MT and develop/move eastward along the front during the afternoon/evening. Forecast soundings suggest only marginal CAPE will develop, but given the strong winds aloft and considerable vertical shear, a few supercell storms are expected capable of large hail and damaging wind gusts. These storms may be rather isolated, but may persist through much of the evening and track quickly eastward into western/central SD. Read more CHECK UPDATE ZOOM GRAPHIC
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