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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, December 17, 2021

SPC Dec 17, 2021 Day 4-8 Severe Weather Outlook

Day 4-8 Outlook Day 4-8 Convective Outlook NWS Storm Prediction Center Norman OK 0355 AM CST Fri Dec 17 2021 Valid 201200Z - 251200Z ...DISCUSSION... ...Monday/Day4 to Tuesday/Day5... A mid-level trough is forecast to amplify as it crosses the Gulf of Mexico on Monday. A surface low is forecast to deepen as it moves across the Gulf and into the northern Florida Peninsula near the end of the period on Monday. More robust low-level moisture will advect northward ahead of this surface low and overspread the entire Peninsula. This will lead to weak to moderate instability by Tuesday morning. Mid-range model guidance has trended more amplified with the mid-level trough in the last few runs. However, there is still uncertainty with the exact solution as the ECMWF has a more consolidated wave and stronger surface low than the GFS, and thus a greater severe weather threat. ...Wednesday/Day6 to Friday/Day8... In the wake of the system which crosses the Florida Peninsula on Tuesday/Day5, northerly flow across the Gulf of Mexico will keep moisture well offshore and thus preclude severe probabilities on Wednesday/Day6 and Thursday/Day7. Some moisture may start to advect northward by Day 8, but there is still considerable uncertainty regarding the upper-level pattern and the quality of moisture return. Read more LIVE: spc.noaa.gov