Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri Sep 22 2023 19:55:01 ACUS01 KWNS 221954 SWODY1 SPC AC 221953 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0253 PM CDT Fri Sep 22 2023 Valid 222000Z - 231200Z ....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS THE NORTH-CENTRAL HIGH PLAINS...AND THE COASTAL MID-ATLANTIC... ....SUMMARY... Severe thunderstorms are possible across parts of the north-central High Plains this afternoon and this evening. A few tornadoes are also possible over the coastal southern Mid-Atlantic/Tidewater region overnight into tomorrow morning. ....20Z Update... ....North-Central High Plains... As mentioned in recently issued MCD #2174, the severe-thunderstorm threat is expected to increase with time across the region this afternoon. Wind profiles will become increasingly favorable for organized storms, and a couple of supercells may evolve with time. Steep midlevel lapse rates and cool temperatures aloft will support large hail of 1.5 to 2 inches in diameter, conditional on supercell development. A tornado or two will also be possible if multiple sustained supercells can develop and mature. Severe Thunderstorm Watch #689 was recently issued to cover the potential risk across the region. ....Coastal southern Mid-Atlantic/Tidewater... No significant changes have been made by NHC to the forecast track of Tropical Storm Ophelia, with the system still expected to be onshore over the central NC coast by 12Z tomorrow. Stable conditions are in place across this region now, but an increasingly moist and buoyant boundary layer is expected to advect into the region overnight. This could support a few stronger convective cores, which, given the strong low-level wind fields, could then produce brief tornadoes. ...Mosier.. 09/22/2023 ..PREV DISCUSSION... /ISSUED 1134 AM CDT Fri Sep 22 2023/ ....North-central High Plains... Scattered thunderstorms are still ongoing at midday across western portions of Nebraska/South Dakota, generally in association with a lead shortwave trough downstream of a more prominent upper trough over the northern Intermountain region. In this wake of this activity, the primary corridor of diurnal destabilization will be focused in a northwest/southeast-oriented corridor across eastern Wyoming into the Nebraska Panhandle and extreme southwest South Dakota. Aided by low-level upslope flow/differential heating and the approach of the upstream trough/speed max, the aforementioned corridor is where at least isolated severe storms are expected to develop into mid/late afternoon, and subsequently move through this relatively narrow corridor of modest instability (MLCAPE 750-1250 J/kg). Long hodographs with 40+ kt effective shear will support supercells capable of large hail (locally significant 2+ inch), and possibly some tornado risk given the relatively moist environment. These storms should spread east-northeastward across much of the north-central Plains tonight, with the potential for large hail and locally damaging winds continuing possibly into the overnight. ....Coastal southern Mid-Atlantic/Tidewater... The potential for supercells and a few tornadoes is expected to increase late tonight as Potential Tropical Cyclone 16 approaches the coast. Reference the National Hurricane Center for the latest track/intensity forecast details. While inland areas are currently stable with respect to surface-based convection, higher theta-e air will accompany a warm front shifting toward the coast late tonight, all while low/mid-level winds strengthen on the northern periphery of the Potential Tropical Cyclone. Supercell-favorable ingredients are expected to be maximized across coastal eastern North Carolina into far southeast Virginia. This is where MLCAPE in the 500-1500 J/kg range is possible, despite midlevel lapse rates only slightly greater than moist adiabatic. Enlarging and well-curved hodographs are expected, with effective SRH of 300-500 m2/s2. A few tornadoes are possible mainly during the overnight into early Saturday. ....Iowa... An MCV continues to drift east-northeastward across western Iowa at midday. While plentiful cloud cover and some showers/thunderstorms precede the MCV, modest destabilization should gradually occur mainly across eastern Iowa this afternoon. Some stronger to locally severe storms could develop accordingly, aided by influences of the MCV. ....Eastern Oklahoma/ArkLaTex... While a few stronger storms could occur today, severe potential is expected to remain very limited across the region as warm advection abates and mid-level lapse rates remain modest. $$ = = = 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) .