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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 31, 2021

SPC Dec 31, 2021 2000 UTC Day 1 Convective Outlook

SPC 2000Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0134 PM CST Fri Dec 31 2021 Valid 312000Z - 011200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS MAINLY AFTER MIDNIGHT FROM SOUTHEAST OK/NORTHEAST TX TO MIDDLE TN/SOUTHERN KY.... ...SUMMARY... Scattered severe thunderstorms remain possible, mainly from late evening into the overnight across parts of the South-Central States towards the Tennessee Valley. ...Northern AL/Northwest GA... There will be a window of opportunity this afternoon for a period of isolated strong/severe storms to affect northern AL and northwest GA, within a weakly forced but favorably sheared environment. Refer to MCD #2089 for further details on this scenario. ...Northeast TX/southeast OK to TN/KY... The ongoing forecast remains on-track, with no changes made. Thunderstorms will begin to develop after 10pm across the SLGT risk area, with the primary severe threat mainly after midnight. Sporadic hail and wind events may occur overnight in this corridor, with the potential for a tornado or two if supercell structures can develop. ..Hart.. 12/31/2021 .PREV DISCUSSION... /ISSUED 1020 AM CST Fri Dec 31 2021/ ...Synopsis... Within a large-scale trough over the western CONUS, one shortwave trough just off the Baja CA coast will eject east-northeast to the southern High Plains tonight, in advance of another shortwave trough digging south-southeastward from the Pacific Northwest to the Desert Southwest. In response to the ejecting Baja trough, lee cyclogenesis is expected across southeast CO and northeast NM. This cyclone will begin to develop eastward along a sharp baroclinic zone late in the period, as cold air damming occurs across the High Plains. ...Northeast TX/southeast OK to TN/KY and the Deep South... A broad warm sector has been established for many days from TX into the Southeast with mid 60s to low 70s surface dew points, and northward spread of this warm sector is expected through tonight into southeast OK/AR/TN/southern KY. There is uncertainty regarding the potential for open warm sector thunderstorm development with minimal forcing for ascent and some lingering convective inhibition. However, if a storm or two manage to become sustained later this afternoon from central MS to northwest GA, the environment will conditionally favor a supercell severe threat. Otherwise, increasing low-level moisture along the consolidating baroclinic zone and strengthening forcing for ascent primarily through low-level warm theta-e advection will lead to increasing storm coverage overnight from north TX/southeast OK east-northeast across AR/TN/KY. Given deep-layer wind fields largely paralleling the baroclinic zone, elevated convection on the cool side of the boundary may pose a threat for sporadic severe hail and wind. Any surface-based storms along or just south of the front will have the potential to develop supercell structures and to produce a few damaging gusts, isolated severe hail, and a couple tornadoes from about 06-12Z. Read more LIVE: spc.noaa.gov
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