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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, March 18, 2022

SPC Mar 18, 2022 2000 UTC Day 1 Convective Outlook

SPC 2000Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0227 PM CDT Fri Mar 18 2022 Valid 182000Z - 191200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM THE LOWER OHIO AND TENNESSEE VALLEYS INTO SOUTHERN GEORGIA AND THE FLORIDA PANHANDLE... ...SUMMARY... Severe thunderstorms are expected through the afternoon and early evening across portions of the Southeast States where damaging winds and a couple tornadoes are possible. Additional isolated severe storms are also possible across parts of the Ohio Valley. ...20z Update... The Enhanced risk has been removed from FL/GA/AL with the 20z update. Stronger ascent will continue to shift northeast of the region, with midlevel subsidence spreading eastward across AL noted in water vapor imagery. Thunderstorms may continue to develop atop east/southeast-advancing outflow across southern GA into northern FL through the remained of the afternoon/early evening in a continued warm advection regime. This activity may occasionally produce strong/locally damaging gusts and/or a tornado. Further north across central/northern AL into Middle TN a conditional severe threat remains possible. A surface warm front extends from northeast MS across central AL as of 19z. Surface dewpoints in the low/mid 60s and clearing skies are aiding in moderate destabilization with MLCAPE values increasing to around 500-1500 J/kg amid moderate vertical shear. Some deepening CU is noted in visible satellite imagery and if a few storms develop in this environment they could pose a threat for strong gusts, hail and a couple tornadoes. However, this activity will also be fighting midlevel subsidence and decreasing large-scale ascent. Will maintain severe probs for a conditional threat as some weak convection is trying to redevelop across western AL as of 19z. Across the Ohio Valley, the only changes to the outlook were to trim the western edge of the Marginal risk based on the current location of the surface low and ongoing thunderstorm activity. ..Leitman.. 03/18/2022 .PREV DISCUSSION... /ISSUED 1130 AM CDT Fri Mar 18 2022/ ...Middle Gulf Coast/Southeast States... A nearly continuous squall line extends at midday from west-central Georgia and southeast Alabama, where it is been elevated this morning, southwestward into far south-central Alabama and the far western Florida Panhandle. This southwestern-most portion is where somewhat more broken bands of storms exists and more buoyant surface-based conducive air resides coincident with dewpoints in the upper 60s/near 70F. Heights will tend to rise this afternoon as the richer low-level moisture otherwise advects east-northeastward toward southeast Alabama/southwest Georgia. Low-level winds will tend to further veer and modestly weaken, but nonetheless remain sufficiently strong for well-organized and rotating storms, which include a tornado and damaging wind risk. ...Middle Mississippi to Ohio/Tennessee Valleys... The main forcing for ascent through afternoon will be related to the northeastward-transition of the mid/upper-level low over the Ozarks at late morning. Although only modest cloud breaks are noted at midday, relatively cool mid-level temperatures in conjunction with 50s F dewpoints will be sufficient for modest surface-based destabilization this afternoon. Arcs of low-topped convection are anticipated along the northern periphery of this weak surface-based buoyancy. 30-40 kt effective bulk shear in addition to some elongation of hodographs should support a few supercells with mid-level updraft rotation and severe hail as the primary hazard. A tornado or two may also occur, particularly near the Lower Ohio Valley portion of the severe risk area. Farther south, a more conditional severe threat is anticipated in the wake of the large MCS across the Deep South. Mid-level subsidence and drying is indicated by most guidance and updrafts will probably struggle along the cold front sweeping east to the south of the Missouri cyclone. Guidance may be somewhat overdone with the degree of boundary-layer moisture return given just how extensive convective overturning has been this morning in Mississippi into Alabama/western Tennessee. Read more CHECK UPDATE ZOOM GRAPHIC