Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri Jun 16 2023 12:54:24 ACUS01 KWNS 161254 SWODY1 SPC AC 161252 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0752 AM CDT Fri Jun 16 2023 Valid 161300Z - 171200Z ....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF THE CENTRAL HIGH PLAINS...SOUTHEAST U.S. AND MID-ATLANTIC... ....SUMMARY... Large hail and damaging thunderstorms winds are possible across parts of the central High Plains, Southeast U.S. and Mid-Atlantic. ....Synopsis... In mid/upper levels, a split-flow pattern will persist -- and move slowly eastward -- between troughing over the Rockies and East Coast States. An anomalously northward-displaced subtropical jet with gradual anticyclonic curvature will extend from the Desert Southwest across parts of OK and north TX, then southeastward to the an area of difluence over the central Gulf Coast and northeastern Gulf. That jet will contribute substantially to deep-layer shear supporting at least isolated severe potential from the southern Plains east-southeastward, while shortwaves ejecting from the mean Western trough support potential over the central High Plains. A strong shortwave trough was apparent in moisture-channel imagery over Lake Huron and Lower MI, preceded by a weaker (but still well-defined) perturbation over the mid/upper Ohio Valley. These features should phase into a single, high-amplitude shortwave trough by 00-03Z over the inland Mid-Atlantic, with the southern part moving offshore from NJ/Delmarva/NC around the end of the period. At the surface, 11Z analysis showed a wavy surface frontal zone from an area of low pressure over northern VA to another low near PKB, then a cold front southwestward to northern AR and southeastern OK, becoming wavy/quasistationary over western north TX to southern NM. The bulk of severe potential today will be south of this boundary, except over parts of the Mid-Atlantic region and AR/OK. ....AR to Gulf Coast... The damaging-wind threat appears most concentrated in the near term across parts of southern AL into the western FL Panhandle, with some uncertainty as to how far east the threat will persist into recovering but still less-unstable outflow air over southeastern AL and the central/eastern FL Panhandle. See SPC Severe Thunderstorm Watch 314 and related mesoscale discussions for near-term coverage of these thunderstorms and associated severe potential. Otherwise, widely scattered thunderstorms in clusters are possible this afternoon and evening within a broad swath from parts of AR and the Mid-South today, southeastward across the lower Mississippi Valley into parts of MS/AL. Beneath the eastern limb of the subtropical jet, a diurnally destabilized boundary layer and low-level warm advection will aid in airmass recovery being outflow from the morning complex, which should extend into the central Gulf Coast area by this evening ahead of any remaining diurnal activity that crossed the lower Mississippi Valley. Within this swath, greater relative concentrations of severe wind/hail remain unclear due to mesoscale uncertainties on boundary strength/orientation by afternoon and evening. A conditional threat for large/damaging hail and locally severe gusts also extends into parts of east and central TX this afternoon and evening along/ahead of the front, but concerns regarding coverage of storms near the upper ridge preclude greater unconditional probabilities at this time. ....Mid-Atlantic... Scattered thunderstorms should organize into a northeast/southwest- oriented band from midday into afternoon and move eastward over the outlook area, with increasing severe potential from the Piedmont across the Fall Line to the coastal plain. Damaging to isolated severe gusts and sporadic large hail are possible. As the phasing mid/upper perturbations shift southeastward to eastward through the day, a preceding field of DCVA/ascent -- now associated with an area of showers and nonsevere thunderstorms across parts of PA/WV/MD Panhandle -- will shift east of the higher terrain. As this occurs, the UVV plume will encounter increasing boundary-layer moisture and diurnal destabilization. The most favorable air mass (with longest destabilization time and greatest CAPE-shear parameter space) will be roughly below the Fall Line from NJ to eastern VA, where forecast soundings show surface dewpoints in the mid 60s F contributing to MLCAPE averaging around 1500 J/kg. Although weak low-level winds/shear will exist in much of the area, backed flow near sea/bay breezes may locally enhance low-level shear and storm-relative winds in the inflow layer. Enough mid/upper flow also will exist ahead of the trough(s) to yield effective-shear magnitudes in the 30-40 kt range in support of convective organization. ....Central High Plains to southern Plains... Scattered thunderstorms are expected to develop preferentially over the Palmer Divide area this afternoon (where heating of the higher terrain erodes MLCINH fastest), but also on at least an isolated basis southward over southeastern CO east of I-25. Severe hail and gusts are possible. Activity may organize into an MCS that sweeps eastward into KS with severe gusts becoming the main threat, but hail still possible. As one shortwave trough over WY pivots northeastward, and a couple more from AZ to northern NM eject northeastward, large-scale ascent will increase over the area, conterminous with diurnal destabilization. Even with vertical mixing, surface dewpoints should remain in the upper 40s and 50s over most of the area, atop steepening low-level lapse rates of a well-mixed subcloud layer. This will contribute to MLCAPE in the 1000-1500 J/kg range. Low- level flow will be mostly weak, but with enough veering in the vertical to elongate hodographs and yield 30-40-kt effective-shear magnitudes. Coalescence of smaller-scale cold pools may lead to a forward-propagational convective complex that augments wind potential, at least until activity encounters enough nocturnal boundary-layer stabilization in west-central KS to reduce the gust potential. Development will be more isolated to widely scattered and intermittent southeastward across the Southern Plains beneath the ridgy mid/upper-level subtropical jet, though deep shear and local boundary lift may contribute to small relative concentrations in severe potential. ...Edwards/Jewell.. 06/16/2023 $$ = = = 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) .