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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.

Thursday, July 22, 2021

SPC Jul 22, 2021 1730 UTC Day 2 Convective Outlook

SPC 1730Z Day 2 Outlook Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1223 PM CDT Thu Jul 22 2021 Valid 231200Z - 241200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR MUCH OF NORTH DAKOTA INTO NORTHERN MINNESOTA... ...SUMMARY... Severe thunderstorms are possible from North Dakota eastward across northern Minnesota, mainly Friday afternoon and evening. Damaging wind gusts and large hail are expected to be the primary severe threats. ...Northern Plains into the Upper MS Valley... An upper trough is forecast to move eastward across portions of AB/SK/MB on Friday, with the southern extension of this trough, and perhaps an embedded vorticity maximum, expected to move from MT into portions of the northern Plains and upper MS Valley by Friday night. The primary surface low will be approaching the western shores of Hudson Bay by Friday evening, with a trailing cold front extending into portions of the northern Plains. A surface wave may develop along the front somewhere across the Dakotas or northwest MN by afternoon. Multiple rounds of convection appear possible across the Dakotas and Minnesota. The first round would be associated with morning convection that will likely be ongoing at the start of the period from the eastern Dakotas into Minnesota. Sufficient heating downstream may allow for some reintensification of the morning convection and perhaps redevelopment of storms along related outflow/surface boundaries. Another round of storms may develop to the west by late afternoon along the cold front, assuming that sufficient recovery can occur in the wake of the overnight/morning activity. Increasing midlevel flow/deep-layer shear ahead of the upper trough and steepening midlevel lapse rates will support potentially organized cells/clusters with both rounds of storms, with hail and damaging wind expected to be the primary hazards. As convection consolidates Friday night, some upscale growth is possible, with thunderstorm clusters and potentially a QLCS spreading into portions of WI and the U.P of MI, posing a threat of at least isolated damaging wind into early Saturday morning. ...Southwest... Monsoonal moisture and a westward-moving upper-level low will support another day of widespread thunderstorms across portions of AZ/NM on Friday. Modestly enhanced midlevel easterly flow to the north of the upper low track will support sufficient effective shear for weakly organized clusters and perhaps a few rotating cells. Widespread cloudiness will tend to limit destabilization in some areas, but isolated instances of hail and strong wind gusts may be possible with the strongest storms. ..Dean.. 07/22/2021 Read more LIVE: spc.noaa.gov