Subj : DAY2SVR: Nws Storm Prediction Center Norman Ok To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sun Aug 06 2023 06:01:38 ACUS02 KWNS 060601 SWODY2 SPC AC 060600 Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 0100 AM CDT Sun Aug 06 2023 Valid 071200Z - 081200Z ....THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF THE CENTRAL/SOUTHERN APPALACHIANS AND THE MID-ATLANTIC STATES... ....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS SEPARATELY ACROSS THE CENTRAL HIGH PLAINS... ....SUMMARY... Severe thunderstorms are possible Monday across portions of the southern Appalachians, mid-Atlantic and northeast U.S. Scattered swaths of damaging gusts are expected with this activity. Additional widely scattered thunderstorms are possible across the central High Plains, posing a risk for large hail and damaging gusts. ....Synopsis... A potent mid/upper shortwave trough this time of year will shift east from the Mid-MS Valley to the Appalachians on Monday. This will bring a band of anomalously strong west/southwesterly flow to the region, with the strongest flow focused from southern PA southward to northern GA and the Carolinas vicinity. At the surface, low pressure will shift east from northern IL into northern OH through evening, before lifting northeast across the lower Great Lakes overnight. A cold front attendant to the surface low will sweep east/southeast across the Midwest, and become positioned from western NY/PA into northern AL/MS by Tuesday morning. Mid 60s to mid 70s F surface dewpoints are forecast across the large warm sector ahead of the cold front and ejecting mid/upper trough. ....OH Valley to Mid-Atlantic... Some areas of showers and cloudiness are possible early in the day across parts of the Mid-Atlantic vicinity in association with an ejecting lead shortwave impulse, continued warm advection and backed low-level flow to the east of a lee surface trough should keep the atmosphere primed for severe thunderstorm potential during the afternoon/evening. Convection is expected to develop by midday closer to the surface front over parts of OH/KY. Multiple bands of convection are then expected into the afternoon with eastward extent into WV/southern PA and the Delmarva. A mix of semi-discrete cells and clusters are possible initially. A risk for all severe hazards is expected given effective shear greater than 40 kt, effective SRH greater than 200 m2/s2 and MLCAPE 1500-3000 J/kg. With time, upscale growth into a bowing MCS is possible across parts of southern PA/WV and into the Delmarva vicinity, posing an Enhanced risk (level 3 of 5) for severe/damaging gusts during the afternoon/evening. Instability will weaken with northward extent into NY and southern New England. However, isolated strong/severe storms posing a risk mainly for strong gusts and perhaps small hail are expected. ....TN Valley to the Carolinas/Southeast vicinity... Thunderstorm clusters are expected to develop from Middle/eastern TN into northern AL/GA by early afternoon. Strong instability with MLCAPE values generally from 2000-4000 J/kg and effective shear magnitudes greater than 40 kt will support vigorous updrafts. Further south from the surface low, deep-layer flow (above 1 km) will generally be unidirectional from the west. Some modest backed low-level flow is forecast, which could support a tornado or two, but convection is expected to grow upscale into a bowing MCS fairly quickly as storms spread east across eastern TN/northern GA and the Carolinas during the afternoon/evening. Convection should gradually weaken as it approaches the coastal Carolinas after dark. Some uncertainty exists with regards to severe potential with southward extent. Deep-layer flow weakens with southward extent, but if southward propagating cluster develops, some wind risk can be expected into southern AL/GA given degree of instability and a very moist airmass/water-loaded downdrafts. ....Central High Plains... Moderate mid/upper northwesterly flow will continue to stream across the central High Plains vicinity on Monday. Moderately cool 500 mb temps around -10 C will support steep midlevel lapse rates. Modest boundary layer moisture is forecast along a surface trough, with dewpoints generally in the 50s, supporting moderate instability. Strong vertical shear (effective shear greater than 45 kt) will foster organized updrafts, while elongated/straight hodographs suggest large hail will be possible. A deeply-mixed boundary-layer with dewpoint depressions around 20 F also may foster strong gust potential. While the boundary-layer will be somewhat on the dry side, backed low-level winds in the vicinity of a weak surface low over northeast CO/NE Panhandle could support a brief tornado in addition to the wind/hail risk. ....Northeast TX toward the Lower MS Valley... A surface boundary is forecast to extend west to east across the region. Differential heating along the boundary, and a very moist/unstable airmass will support isolated thunderstorm development. Vertical shear will be rather weak, but isolated strong gusts may accompany thunderstorms during the afternoon. Isolated coverage/longevity of this activity preclude higher risk probabilities at this time. ...Leitman.. 08/06/2023 $$ = = = 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) .