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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.

Tuesday, December 13, 2022

SPC Dec 13, 2022 0600 UTC Day 1 Convective Outlook

LIVE MAP (ABOVE) ... SPC 1200Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1156 PM CST Mon Dec 12 2022 Valid 131200Z - 141200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF EASTERN TEXAS...LOUISIANA...AND INTO THE LOWER MISSISSIPPI RIVER VALLEY... ...SUMMARY... Severe thunderstorms capable of all severe hazards including tornadoes, some strong, are possible from parts of east Texas to the Lower Mississippi Valley area today and tonight. ...Synopsis... An anomalously deep upper-level cyclone centered over the Plains states is forecast to shift slowly eastward today and tonight while 90-100+ kt of mid-level flow overspreads the Mississippi River Valley and Gulf Coast. A sub 1000 mb surface low across northern KS and southern NE will continue to advect a partially modified Gulf airmass inland ahead of a fast moving cold front. Rapid destabilization and strong vertical shear beneath a 50+ kt 850 mb jet will support a risk for all severe hazards over a wide area from early this morning through the overnight hours. ...Central OK into central TX ... Early in the forecast period a broken band of thunderstorms is expected to be ongoing from central OK south toward the I-20 corridor into central TX. Likely just ahead of the surging Pacific front, strong poleward advection of modified Gulf moisture will support modest destabilization in the absence of robust surface heating. Area RAP soundings show meager MUCAPE around 500 J/kg from central OK south toward the Red River vicinity where values increase to 1000-1500 J/kg. In combination with sufficient buoyancy, very strong shear profiles are expected through the morning hours beneath a 50+ kt low-level jet. Storm organization into a broken linear band/QLCS with embedded supercell structures appears likely. With 0-1km SRH in excess of 250-300 m2/s2 damaging wind gusts and tornadoes will be possible. Confidence is greatest in a sustained severe risk near and south of the Red River valley where the best overlap of strong forcing for ascent and surface destabilization is expected. ...ArkLaTex into the Lower MS River Valley... As the main frontal band continues east through the early afternoon, strong low-level warm advection is expected ahead of it as a warm front lifts north through southeastern OK and into central AR. To the south, low to mid 60s F surface dewpoints will stream northward reaching the AR/LA border by 21z. Dense stratus cover in the warm advection region will likely forestall surface heating, but the combination of surface moistening and cooling aloft should result in more favorable thermodynamics with time. As the low-level jet shifts eastward through the afternoon and evening low-level hodographs should expand favorably for supercells capable of all severe hazards. Storm mode remains somewhat uncertain with weak capping and strong warm advection taking place ahead of the frontal band. HREF guidance suggests the squall line may reorganize into more semi-discrete elements with additional development possible ahead in the warm sector with time as better thermodynamics are realized. 0-1km shear values in excess of 35 kt will be strongly supportive of low-level updraft rotation and some strong tornado risk may evolve if semi-discrete supercells are able to develop. Otherwise, embedded circulations capable of strong winds and tornadoes are expected. The northern extent of the severe risk also remains unclear and tied to destabilization with advection of the richer boundary-layer moisture. Faster model solutions suggest storms may remain severe across portions of northern MS into early Wednesday morning. While thermodynamics are likely to be marginal, very strong low and mid-level shear profiles will support a mix of supercells and short line segments capable of damaging gusts. Farther south across southeastern LA and southwest MS, continued onshore advection of the moist and unstable Gulf airmass will likely keep the severe risk ongoing through the night. Large and mostly streamwise low-level hodographs (0-500m SRH 200+ m2/s2) will favor supercells and a risk for nocturnal tornadoes. ..Lyons/Kerr.. 12/13/2022 Read more CHECK UPDATE ZOOM GRAPHIC