SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0750 AM CDT Fri Jul 07 2023 Valid 071300Z - 081200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE OKLAHOMA/TEXAS PANHANDLES INTO WESTERN OKLAHOMA... ...SUMMARY... Scattered severe thunderstorms are expected today through tonight across portions of the central and southern Plains. Large to very large hail and severe/damaging winds should be the primary risks, with the greatest potential for significant (75+ mph) winds across parts of the Oklahoma/Texas Panhandles into western Oklahoma this afternoon and evening. ...Central/Southern Plains... An MCS ongoing this morning across parts of western/central OK should continue to weaken over the next couple of hours as it moves eastward and away from a southerly low-level jet over the southern/central High Plains. A convectively reinforced boundary in the wake of this MCS is present across parts of western north TX into the TX Panhandle and northeastern NM. This boundary, along with higher terrain across the southern/central Rockies, should provide a focus for renewed severe thunderstorms later this afternoon and evening. High-based convection should initially form across parts of central/southeastern CO and northeastern NM in a weak low-level upslope regime. With enhanced mid-level westerly flow remaining over much of the southern/central Plains, deep-layer shear will be more than enough to support supercells. These supercells should pose some threat for very large hail given the presence of steep mid-level lapse rates amid moderate to strong instability and a favorable shear profile. A small but intense bowing complex appears likely to develop in tandem with a strengthening low-level jet late this afternoon and evening across parts of the OK/TX Panhandles into western OK. Significant severe winds of 75+ mph may occur with this complex as it moves quickly eastward. The eastern extent of this wind threat remains uncertain given the potentially stabilizing effects of the morning MCS across central OK. Other supercells may form in the strengthening warm advection regime across southern KS/northern OK this evening. Very large hail appears possible with these thunderstorms with strong MUCAPE and deep-layer shear forecast. Some threat for severe/damaging winds may eventually develop with this convection if it can grow upscale into one or more small clusters while spreading generally southeastward tonight. ...Northern Plains/Upper Midwest... A weak cold front will move south-southeastward across parts of the northern Plains and Upper Midwest today. This region will remain on the southern periphery of an upper trough/low over central Canada towards Hudson Bay. Although low/mid-level flow should remain fairly modest, limiting deep-layer shear, thunderstorms which develop along the front may still produce occasional strong to severe wind gusts as they spread south-southeastward through early evening. Isolated large hail may also occur with initially more robust updrafts along the front where instability is forecast to be greatest this afternoon. Convection should quickly weaken with eastward extent with the loss of daytime heating. ...Central Plains into the Mid Mississippi Valley... An elevated cluster of thunderstorms is ongoing this morning across parts of central/eastern NE. These thunderstorms are being aided by warm/moist advection associated with a southerly low-level jet, and ascent attendant to a westerly mid-level jet over the central Plains. The airmass downstream into the mid MS Valley is not particularly unstable at the moment, which along with the weakening low-level jet, should keep any severe threat quite marginal/isolated this morning. Even so, renewed convective development may eventually occur across parts of eastern KS into MO later today as instability gradually increases. Multicell clusters should be the primary thunderstorm mode, but a transient supercell or two appears possible as deep-layer shear strengthens to around 30-40 kt. Isolated severe/damaging winds and some hail may occur with this convection as it spreads eastward towards the MS River through this evening. ...Northeast/Mid-Atlantic... Daytime heating of a moist low-level airmass should encourage the development of weak to moderate instability by this afternoon across parts of the Northeast and Mid-Atlantic. Glancing ascent associated with a shortwave trough over Quebec and weak low-level convergence along a surface trough will likely foster at least scattered thunderstorm coverage this afternoon and evening. Deep-layer shear is forecast to remain fairly modest, generally 20-30 kt or less, and weakening with southward extent across the Mid-Atlantic. Still, some loosely organized thunderstorm clusters should develop and move east-northeastward while posing an isolated threat for strong to damaging winds. ..Gleason/Leitman.. 07/07/2023
