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Archives for the SPC Convective Outlook are updated daily (approximately) with a live map at the beginning of each article. Follow the link at the end of the article to check for current updates on the NOAA/NWS Storm Prediction Center website. Also, see Archives for Chicago's hourly weather data on CARDINAL NEWS Magazine.


Tuesday, June 21, 2022

SPC Jun 21, 2022 2000 UTC Day 1 Convective Outlook

SPC 2000Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0256 PM CDT Tue Jun 21 2022 Valid 212000Z - 221200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS NORTHEAST KANSAS TO SOUTHEAST IOWA... ...SUMMARY... Isolated to scattered damaging winds and isolated large hail will be possible from northeast Kansas to southeast Iowa between about 5 to 10 PM CDT. A broad cu field has developed from northwest Missouri into north-central Wisconsin along and ahead of a cold front in the region. Thus far, only occasional robust convective attempts have occurred, and failed across Wisconsin. Expect this trend to continue given the veered surface flow ahead of the cold front across the region. However, if any storms can develop, the environment is favorable for strong, rotating updrafts with MLCAPE around 2500 J/kg and ~35 knots of effective shear per SPC mesoanalysis. Farther southwest, more northerly post-frontal winds have resulted in stronger convergence which should lead to more convective coverage than farther north. Between 1930-20Z, a more confined line of cumulus has developed across northeast Kansas per visible satellite. This likely represents the frontal location and should provide the focus for thunderstorm development this evening. Latest HRRR solutions indicate thunderstorm development between 22-23Z which seems appropriate based on satellite trends. Multicell clusters remain the expected storm mode with a primary threat for damaging winds. ..Bentley.. 06/21/2022 .PREV DISCUSSION... /ISSUED 1127 AM CDT Tue Jun 21 2022/ ...Central KS to IA/IL/WI border area... A corridor of boundary-layer dewpoints in the upper 60s to lower 70s will be maintained immediately ahead of a cold front, trailing off with western extent into KS where it intersects the dryline. Large buoyancy with MLCAPE from 2000-3500 J/kg will likely develop amid hot surface temperatures warming into the mid to upper 90s from northeast KS northeastward, with lower buoyancy but a deeper-mixed boundary layer into central KS. While the entire region will remain well removed from the direct influence of a shortwave trough over southern Manitoba moving into northwest Ontario, an MCV over NM will drift towards the south-central High Plains. A belt of confluent mid-level southerlies ahead of this feature transitioning to modest west-southwesterlies with northeast extent on the periphery of stronger flow over the north-central states may provide sufficient deep-layer shear for multicell clustering with convection that develops along the front. This appears most probable from northeast KS into southeast IA where steep low-level lapse rates and DCAPE to near 1500 J/kg would favor isolated to perhaps scattered downbursts producing 50-70 mph wind gusts during the early evening. Isolated quarter to golf ball-sized hail should be a secondary threat in terms of coverage and most likely with initial robust updrafts. ...Eastern Upper/northern Lower MI into eastern WI... Low-level convergence is consistently forecast to remain weak along this portion of the cold front pushing east across the region, with largely veered winds. As such, signals for convective development are sparse across morning guidance. Nevertheless, stronger deep-layer flow along with a plume of steep mid-level lapse rates will support a conditionally favorable setup for isolated severe hail and wind. Read more CHECK UPDATE ZOOM GRAPHIC
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