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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.


Friday, July 28, 2023

SPC Jul 28, 2023 1630 UTC Day 1 Convective Outlook

LIVE MAP (ABOVE) ... SPC 1630Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1120 AM CDT Fri Jul 28 2023 Valid 281630Z - 291200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS LATER THIS AFTERNOON INTO EARLY TONIGHT FROM NORTHERN IA TO NORTHERN IN AND VICINITY... ...SUMMARY... Severe storms are most probable from Iowa and southern Minnesota eastward to northern Illinois/southern Wisconsin late this afternoon/evening, and continuing into southwest Lower Michigan and northern Indiana tonight. Damaging winds and large hail are the main threats. ...SD/NE to the Upper Midwest through tonight... Within a largely zonal flow regime, embedded speed maxima will move eastward over the central/northern Plains and the upper MS Valley - the most pronounced of which is now over ND. Convection and an outflow/frontal surge with this ND speed max will eventually interact with the north edge of the more moist/unstable air mass from southeast SD/southern MN into northern IA/southern WI later this afternoon/evening. The timing of convective initiation and details of subsequent storm evolution are both somewhat in question, but effective bulk shear near 50 kt and MLCAPE of 2500-4000 J/kg will conditionally favor splitting supercells initially with very large hail. Convection could then grow upscale into an MCS this evening into tonight, with an attendant threat for damaging winds. ...Upper OH Valley into the Mid-Atlantic this afternoon/evening... A remnant MCV over northern IN will move eastward over OH today, and additional convection expected today along the associated outflow boundary/differential heating zone across central/eastern OH. The stronger flow with the MCV will tend to trail the lead outflow, so multicell storms with occasional downburst winds will be the primary threat this afternoon. Farther east, vertical shear will be weak, but surface heating over the higher terrain and weak convergence along a diffuse baroclinic zone will support scattered thunderstorm development this afternoon from the central Appalachians into parts of the Mid-Atlantic. Isolated strong downburst winds for a few hours this afternoon/evening will be the main concern this area. ...Northern ME this evening... A northern stream shortwave trough and associated surface cold front will cross Quebec and northern ME later this afternoon into this evening. Midlevel lapse rates will not be steep, but MLCAPE near 1000 J/kg and relatively long hodographs will support the potential for wind damage with a band of storms along and just ahead of the cold front. ...Southern MT to northeast CO and vicinity through tonight... Subtle speed maxima will move around the northern periphery of the southern Rockies midlevel high, interacting with terrain circulations and a deepening mixed layer later this afternoon. High-based storm development is expected around mid afternoon from southern MT to southeast WY/northeast CO, where storm clusters will move off the high terrain in response to mid-upper westerlies, and inverted-V profiles will favor isolated strong-severe outflow gusts as the main concerns. ..Thompson/Weinman.. 07/28/2023 Read more CHECK UPDATE ZOOM GRAPHIC
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CHICAGO UTC-6 during CST (Central Standard Time, e.g., winter)
CHICAGO UTC-5 during CDT (Daylight Savings Time, e.g., summer)