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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 31, 2021

SPC Dec 31, 2021 0600 UTC Day 1 Convective Outlook

SPC 1200Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1159 PM CST Thu Dec 30 2021 Valid 311200Z - 011200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE ARKLATEX...MID MISSISSIPPI...OHIO AND TENNESSEE VALLEYS... ...SUMMARY... Thunderstorms associated with severe weather will be possible today and tonight from the southern Plains and Arklatex east-northeastward into the mid Mississippi, Ohio and Tennessee Valleys. A few tornadoes along with isolated large hail and wind damage are expected. ...Southern Plains/Arklatex/Mid Mississippi Valley... West-southwesterly mid-level flow will be in place today across much of the central and eastern United States as a subtle lead shortwave trough moves across the southern Plains. At the surface, a moist airmass will be located from the southeastern third of Texas east-northeastward into the lower to mid Mississippi Valley. Thunderstorm development will be likely along the northern edge of this moist airmass this afternoon from north Texas into southeast Oklahoma with this activity moving into Arkansas late this afternoon. Weak instability, strong deep-layer shear and adequate forcing should be enough for an isolated severe threat. However, uncertainty exists concerning the magnitude of the severe threat. A lack of low-level convergence should keep the severe threat more isolated this afternoon. This evening into tonight, conditions for severe storms will rapidly become more favorable as a shortwave trough moves quickly through the southern High Plains. Low-level convergence will increase along the northern edge of the moist airmass as a low-level jet strengthens across the southern Plains and Arklatex. Scattered thunderstorms are expected to develop in the Red River Valley during the late evening along the northern edge of the low-level jet. Thunderstorms will also likely develop eastward into the Ozarks. NAM forecast soundings from 08Z to 10Z along this corridor have 0-6 km shear near 80 kt with 0-3 km helicity approaching 400 m2/s2. This should be favorable for supercells and a couple tornadoes. Supercells should also be capable of producing wind damage and large hail. ...Ohio and Tennessee Valleys... West to west-southwesterly mid-level flow will be in place today from the lower to mid Mississippi Valley eastward to the Atlantic Seaboard. A moist airmass will be located across much of the Tennessee Valley this afternoon where surface dewpoints should be in the mid 60s F. As weak instability increases during the afternoon, isolated thunderstorms are expected to develop from Tennessee into southern Kentucky. Strong deep-layer shear should support an isolated severe threat with the initial activity. This convection could struggle at first due to a lack of low-level convergence. However, the severe threat should gradually ramp up during the evening as a low-level jet strengthens and a fast-moving shortwave trough approaches from the west. Thunderstorms are expected to gradually increase in coverage during the mid to late evening from western Kentucky into western Tennessee. Forecast soundings in western Tennessee from 06Z to 09Z show MLCAPE in the 500 to 750 J/kg range with 0-6 km shear near 70 kt. This combined with increasing low-level convergence and a strengthening low-level jet will likely support severe storm development this threat continuing into the overnight period. Storms that develop along the northern edge of the low-level jet will move east-northeastward across the Ohio and Tennessee Valley with a threat for a couple tornadoes, wind damage and isolated large hail. ..Broyles/Lyons.. 12/31/2021 Read more LIVE: spc.noaa.gov
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