Subj : DAY1SVR: Enhanced Risk To : All From : Mike Powell Date : Thu Jul 06 2023 15:50:00 ACUS01 KWNS 061948 SWODY1 SPC AC 061946 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0246 PM CDT Thu Jul 06 2023 Valid 062000Z - 071200Z ....THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FOR NORTHEAST COLORADO INTO SOUTHWEST KANSAS... ....SUMMARY... The most concentrated corridor of severe storms is expected across a portion of eastern Colorado and western Kansas, centered on this evening. These storms will be capable of producing very large hail, a few tornadoes, and significant severe wind gusts as they likely evolve into a cluster tracking towards northwest Oklahoma overnight. ....20Z Update... The primary change to this outlook was to disconnect Marginal risk probabilities from the southern Plains to the Lower MS Valley. The probabilities in the Lower MS Valley were adjusted to address the shorter-term large hail/strong gust threat with storms intensifying over the Arklatex toward MS. Meanwhile, the marginal risk probabilities in the southern Plains were terminated southeast into central OK, where an MCS should be positioned at the end of the period (12Z Friday morning). Finally, the 30 percent hail probabilities (and associated Enhanced Risk line) have been extended slightly northwest into northern CO, where persistent insolation may promote locally higher buoyancy and subsequent supercell hail threat. Otherwise, the previous forecast (see below) remains on track. ...Squitieri.. 07/06/2023 ..PREV DISCUSSION... /ISSUED 1130 AM CDT Thu Jul 06 2023/ ....Eastern CO to northwest OK... Decaying remnants of a morning MCS and elevated clusters persist across parts of OK, the far eastern TX Panhandle, and western KS. Abundant cloud coverage from convective debris and a broken stratus canopy will modulate boundary-layer heating, with more robust insolation expected over much of the TX Panhandle and in pockets along the southern Rockies. With a southeasterly component to low-level flow confined to the lowest 1 km and pronounced veering of the wind profile with height to separate confluent belts of enhanced mid-level westerlies centered on the WY/CO border and the CO/NM border, late afternoon thunderstorm development should be focused near the Denver cyclone with capping potentially limiting development over the Raton Mesa. Initial updrafts in northeast CO will likely evolve into one or two slow-moving supercells with very large hail as the main threat early. A strengthening low-level jet this evening should support maintaining these supercells after dusk and/or yield additional development east along the Palmer Divide in east-central CO. Despite increasing MLCIN, low-level hodographs will become quite enlarged, supporting potential for a long-track intense supercell or two moving southeast across a portion of eastern CO and western KS. Overnight, elevated convective development should occur downstream of these long-track supercells, which may yield a small bowing MCS focused on southwest KS to northwest OK. The overall tornado and significant severe wind threat should be modulated to an extent by relatively weak low-level lapse rates. But the highly sheared and steep mid-level lapse rate environment renders concern for a narrow swath of significant severe persisting into early morning. ....Lee of the Big Horns to the Black Hills vicinity... Farther north, a separate region of more concentrated thunderstorm development is expected during the late afternoon to evening downstream of a low-amplitude shortwave trough moving east from the northern Rockies towards the Big Horns. Low-level shear will be weak across this area, but an elongated nearly straight-line hodograph will foster a few splitting supercells capable of very large hail. These should consolidate into an east-southeast moving cluster/small MCS across western SD and the NE Panhandle with a threat for severe wind gusts peaking during the mid-late evening and becoming more isolated overnight. ....Ark-La-Tex to Ark-La-Miss vicinity.. An MCV over east-central OK should drift east with regeneration of thunderstorms downstream to its south and southeast impinging on a confined plume of MLCAPE from 2000-3000 J/kg. Despite relatively weak shear, semi-organized multicell clusters should form and offer a risk for isolated damaging winds through this evening. $$ --- SBBSecho 3.14-Linux * Origin: Ilink: CCO - capitolcityonline.net (454:1/105) .