Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed Jun 07 2023 12:49:50 ACUS01 KWNS 071249 SWODY1 SPC AC 071248 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0748 AM CDT Wed Jun 07 2023 Valid 071300Z - 081200Z ....THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE SOUTHERN HIGH PLAINS...NORTHWEST...NORTHEASTERN PLAINS...LOWER TO MID MISSOURI VALLEY...COASTAL CAROLINAS...AND FLORIDA... ....SUMMARY... Marginally severe thunderstorms, associated with strong winds and hail, will be possible today across parts of the southern High Plains, Northwest, northeastern Plains, lower to mid Missouri Valley, coastal Carolinas, and Florida. ....Synopsis... Another day of large-scale blocking aloft will characterize the mid/upper-level pattern, with mean ridging over the central CONUS and a large, zonally elongated cyclone over the Northeast, Great Lakes and much of the East Coast. The associated 500-mb low is expected to retrograde slowly westward from its present position over NB, across ME toward the northern fringes of NH/VT through the period. A weak 500-mb high remains over the northern Plains, anchoring the mean ridge, while a quasistationary trough/height weakness persists from the central Rockies southeastward over the southern High Plains, and across the mean ridge to south TX. This is connected loosely to an area of cyclonic flow over the central Gulf, which includes a weak shortwave trough, from the Gulf north of the Yucatan Channel south-southwestward over the Yucatan peninsula. This perturbation should move east-northeastward over portions of central/south FL by 00Z. Meanwhile, a mid/upper-level low over south-central CA will weaken slowly and drift eastward toward the TPH-LAS vicinity by 12Z tomorrow. At the surface, 11Z analysis showed a quasistationary to slow-moving cold front over the southern Delmarva Peninsula, southern WV, and northern KY, curving northwestward across southern IL, northeastern MO, northwestern IA, and extreme eastern ND. The segment of this boundary east of the Blue Ridge should move southward across the remainder of VA and into NC buy the end of the period. Another, preceding front was drawn across coastal NC and central SC, and should shift southeastward through the day as well. ....Coastal Carolinas and vicinity... Widely scattered to scattered thunderstorms should develop this afternoon near the leading front, with isolated development possible to its south. Associated multicells should move eastward to southeastward over the outlook area, offering damaging to marginal severe gusts and isolated hail. Although the westerly/front- parallel flow component at the surface will limit both low-level shear and frontal convergence, MLCINH should be weak, allowing even reduced lift to support convective initiation. Favorable low-level moisture is expected, with 60s F surface dewpoints and diurnal heating underlying -11 to -12 deg C 500-mb temperatures in the southern rim of the broad cyclonic-flow field aloft. The result should be around 1000-1500 J/kg MLCAPE -- locally/briefly higher -- with 25-35-kt effective-shear magnitudes. .....FL... Scattered thunderstorms should develop from midday through afternoon along sea-breeze boundaries, as well as subsequent outflow boundaries and their intersections. The West Coast boundary should be displaced well eastward/inland before the bulk of its convection forms, given the predominantly westerly boundary-layer wind component. Strong surface heating and rich moisture -- with dewpoints commonly in the upper 60s to low 70s F -- will underlie a deep troposphere and strong anvil-level flow related to the subtropical jet. Subtle large-scale ascent ahead of the Gulf perturbation also will contribute to a convectively favorable environment in this area. A few organized multicells with hail and/or water-loaded downdrafts are possible, before activity diminishes in the evening due to expansive outflow and nocturnal cooling. ....Lower to Mid Missouri Valley/Northeastern Plains... A narrow plume of favorable moisture and lift near the front will contribute to potential for widely scattered thunderstorms mainly this afternoon. Isolated, marginally severe gusts and hail are possible. The moist plume should be characterized by surface dewpoints often remaining in the 60s F today, even through diurnal heating/mixing of the boundary layer. This should offset modest mid/upper-level lapse rates enough to support around 800-1500 J/kg MLCAPE, atop steep low-level lapse rates. Weak deep-layer winds/ shear will be present, but the low-level thermodynamic profile should support maintenance to the surface of some strong-severe hail and downdrafts. ....Southern High Plains to Big Bend... Scattered thunderstorms are expected to develop again today across this region, offering marginally severe gusts and hail from the most intense cores. A strongly heated and favorably moist boundary layer will underlie only weak MLCINH, under an EML that remains poorly developed for the time being. Still, steep low/middle-level lapse rates of 8-8.5 deg C/km are forecast, combining with mid 40s to mid 50s F surface dewpoints at 4000+ ft MSL elevations of the western parts of the outlook area, to yield MLCAPE in the 1500-2500 J/kg range. Proximity to the upper ridge will keep deep-layer flow and shear weak over most of the region, though the prevailing/light westerly component should encourage eastward movement (and perhaps some clustering and cold-pool organization on smaller scales). Enough deep shear may persist across the Davis Mountains/Big Bend region -- under the north rim of the subtropical jet -- to support a right-moving supercell or two, with a conditional risk of isolated significant hail. Severe potential may persist across the lower Pecos Valley and Permian Basin of west TX, as well as South Plains and western Panhandle farther north, before the nocturnal weakening of this convection. ....Interior Northwest... With a rather stagnant upper pattern and similar to slightly greater low-level moisture over the area compared to yesterday, another round of isolated to scattered afternoon thunderstorms is expected to develop under strong difluence aloft to the northeast of the CA cyclone. Development will be supported by moisture equivalent to 50s surface dewpoints at lower elevations, along with diurnal heating (especially over windward slopes). Convection should fan out mostly northward over eastern parts of the outlook area and northwestward to westward elsewhere, offering strong/isolated severe gusts through a well-mixed subcloud layer characterized by steep lapse rates. Isolated hail near severe limits also cannot be ruled out. ...Edwards/Smith.. 06/07/2023 $$ = = = To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM. --- SBBSecho 3.14-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .