Severe Storm Outlook Narrative (AC)
Issued by NWS
Issued by NWS
423 ACUS02 KWNS 031711 SWODY2 SPC AC 031710 Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1210 PM CDT Wed Jul 03 2024 Valid 041200Z - 051200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF EASTERN KANSAS...NORTHEAST OKLAHOMA...AND THE OZARKS...AS WELL AS PARTS OF THE UPPER MISSISSIPPI VALLEY... ...SUMMARY... Severe thunderstorms will be possible on Independence Day, mainly across parts of the Upper Mississippi Valley, Ozarks, and south/central Plains. ...Synopsis... An upper trough over the northern/central Plains will deepen and develop a closed low as it shifts east into the Upper Midwest/Mid-MS Valley vicinity Thursday into Thursday night. Meanwhile, a convectively enhanced vorticity max/lead shortwave impulse in the vicinity of MO Thursday morning will develop eastward across the Ohio Valley and Mid-Atlantic. At the surface, a cold front will develop east/southeast across the central/southern Plains, and the Mid/Upper MS Valley vicinity. Ahead of the front, a seasonally moist airmass will be in place, with 60s to low 70s F dewpoints widespread from the central/southern Plains into the Midwest and eastern U.S. The surface cold front, potential outflow and an MCV over the Mid-MS/OH Valley, and the upper trough/shortwave impulses will provide support for scattered strong to severe thunderstorms across portions of the Midwest into the Mid-Atlantic vicinity on Thursday. ...IA/MN/WI/northern IL Vicinity... A weak surface low will develop eastward across the Upper Midwest during the afternoon/early evening as the northern Plains upper trough shifts east. A cold front will extend into western MN into eastern NE by midday. Ahead of the front, a seasonally moist airmass will be in place with temperatures warming into the upper 70s to low 80s. Modestly steep midlevel lapse rates will further aid in weak to moderate destabilization during the afternoon (MLCAPE 1000-1500 J/kg). Vertical shear will be somewhat modest, around 25-35 kt, but will be sufficient for organized cells and a few transient supercells. Furthermore, elongated/straight forecast hodographs in combination with favorable instability parameters suggest isolated hail up to 1.75 inches diameter will be possible in addition to sporadic gusty thunderstorm winds. Given potential for severe hail, probabilities have been increased and a Slight risk (level 2 of 5) has been included for portions of the region. ...Central/Southern Plains to Mid-MS and Lower OH Valley Vicinity... Convection may be ongoing Thursday morning as a continuation from the Day 1/Wednesday period. This activity will likely result in outflow across the Ozarks and an MCV floating east across the Lower OH Valley. Vertical shear will remain weak over the OH Valley, and heating limited given early clouds and precip. However, a very moist airmass will result in weak to moderate destabilization in pockets of stronger heating. Thunderstorm clusters will pose a risk for sporadic strong gusts through the day as the convectively enhanced vorticity maxima migrates across the area. As the surface cold front advances east/southeast into northern OK and northwest MO by mid/late afternoon, additional thunderstorm development is expected across the recovering airmass over MO and along the strong differential heating gradient extending southward into OK. A very moist airmass will allow for moderate to strong destabilization amid 40+ kt effective shear magnitudes. Organized clusters/bands of storms will develop southeast ahead of the cold front, posing a risk for isolated to scattered strong/locally damaging gusts into the evening hours from eastern KS/OK into MO. Stronger cells may also pose an isolated risk for hail. More isolated, less-organized but still strong convection is expected with westward extent along the surface boundary across parts of western/central OK into the TX Panhandle. A few strong to severe gusts may accompany this activity. ...Mid-Atlantic Vicinity... Low-level warm advection and modest midlevel ascent will support isolated to scattered diurnal thunderstorms in a modestly unstable airmass. Vertical shear will be modest but sufficient for transient storm organization. High PW values, weak low-level flow and steep low-level lapse rates will support sporadic strong downbursts. ..Leitman.. 07/03/2024 $$