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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.

Friday, April 29, 2022

SPC Apr 29, 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 Fri Apr 29 2022 Valid 292000Z - 301200Z ...THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS THIS AFTERNOON AND EVENING OVER PORTIONS OF SOUTHEAST NEBRASKA AND NORTHEAST KANSAS... ...SUMMARY... A complex and significant severe weather episode is forecast this afternoon into tonight across the central Great Plains vicinity. ...Discussion... Only two minor changes were made to the previous convective outlook. 1) Made slight adjustments by sharpening the severe probability gradient for parts of the dryline to reflect dryline position and developing high-based cumulus. 2) Added low hail probabilities for parts of eastern CO. For short-term details regarding expected thunderstorm development and associated severe hazards, reference MCDs 580-582. ..Smith.. 04/29/2022 .PREV DISCUSSION... /ISSUED 1119 AM CDT Fri Apr 29 2022/ ...Southeast NE/Northeast KS... Morning water vapor imagery shows a negatively tilted upper trough over the central Rockies emerging into the High Plains. An associated 60+ knot mid-level jet will move across KS this afternoon, aiding surface cyclogenesis and resulting in a favorable setup for severe storm development. Backed low-level winds to the north/east of the surface low and warm front, along with persistent moisture convergence and mid-level capping through the early afternoon will result in a corridor of boundary layer moisture "pooling" roughly along the KS/NE border. Forecast soundings in this corridor show very favorable parameters for tornadic supercells, but given the strong forcing that will overspread the area, it is uncertain how long supercells can be maintained before linear structures develop. Regardless, significant tornadoes, destructive wind gusts, and very large hail are possible with the storms that move across southeast NE and far northeast KS this afternoon and evening. ...Eastern KS along the dryline... By late afternoon, the surface dryline is expected to extend from the surface low over north-central KS to near ICT. Temperatures west of the dryline will warm to near 90F, while mid 60s dewpoints are maintained to the east. While there is still uncertainty whether many storms form along this axis, most of the 12z CAM guidance now shows at least isolated supercell development over parts of this area. Strengthening southerly low-level flow/shear by early evening would support the potential for strong tornadoes, along with very large hail and damaging winds from the most intense storms. By mid-evening, the surface cold front will overtake the dryline, leading to widespread thunderstorms capable of large hail and damaging winds. The MDT risk area has been expanded slightly southward to include parts of this area, and a 15% tornado risk area has been added. ...Central OK along the dryline... The uncertainty of convective initiation increases south of the KS/OK border, but most CAM guidance shows one or more isolated supercells forming along the dryline somewhere over OK by late afternoon/early evening. Forecast soundings show an uncapped air mass along a somewhat convergent dryline, underscoring the potential for development. Have maintained the SLGT/ENH risk areas across this region with a conditional risk of very large hail and tornadoes from any supercell that can form on the dryline today. Read more CHECK UPDATE ZOOM GRAPHIC
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