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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.


Thursday, May 27, 2021

SPC May 27, 2021 1300 UTC Day 1 Convective Outlook

SPC 1300Z Day 1 Outlook Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0744 AM CDT Thu May 27 2021 Valid 271300Z - 281200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS SOUTHERN GREAT PLAINS TO OZARKS... ...SUMMARY... Scattered severe thunderstorms are expected from parts of the southern Great Plains into the Ozarks and Mid-Mississippi Valley. Significant damaging winds, very large hail, and a few tornadoes are possible. ...Southern Great Plains to Mid-MS Valley... Most guidance has poorly simulated overnight convection along with the stabilizing impacts of ongoing and decayed convection in parts of the open warm sector. Confidence is greatest in a strongly unstable air mass with MLCAPE in excess of 2500 J/kg developing from west TX into most of OK this afternoon where upper 60s to low 70s surface dew points persist beneath the eastern extent of the elevated mixed-layer. Lesser confidence exists in the amplitude of destabilization with northeast extent into the Mid-MS Valley given a combination of lesser boundary-layer moisture, weaker mid-level lapse rates, and/or residual cloud cover. Guidance that has more closely simulated the elevated convection in the northwest OK/south-central KS vicinity generally suggest increasing coverage this morning as low-level warm/moist advection persists in the wake of earlier decayed convection. This activity should eventually impinge on richer boundary-layer moisture towards north-central/northeast OK, yielding a potential severe threat as early as midday. One or more clusters with embedded supercells should develop east towards the Ozarks and south towards the Red River through the afternoon. Additional supercells should form along the dryline by mid to late afternoon in the afternoon from the TX Trans-Pecos north to the intersection with the cold front/leading outflow near the southeast TX Panhandle into western OK. Large hail (some very large) will be most pronounced with supercells, while amalgamating cold pools should support a significant severe wind threat by late afternoon continuing into the evening. A few tornadoes are also possible particularly in interactions with storm-scale outflows owing to relatively modest low-level shear. Timing of transition to severe, as well as how far south convection will develop prior to peak surface heating, lowers confidence in attempting to identify a mesoscale corridor of greater hazard probabilities with this outlook cycle. Farther northeast across the Lower MO to Mid-MS Valley, multiple MCVs are evident with leading convection in northeast MO rather poorly simulated by guidance. Confidence is fairly low that the degree of destabilization indicated by guidance will truly be achieved downstream across the Mid-MS Valley, as well as over the Lower MO Valley where an attempt at air mass recovery may occur ahead of the impinging cold front. Nevertheless, favorable deep-layer shear and ascent downstream of the northern Great Plains shortwave trough will support a conditional severe threat through this evening. ..Grams/Mosier.. 05/27/2021 Read more LIVE:
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