Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Thu May 18 2023 19:55:40 ACUS01 KWNS 181955 SWODY1 SPC AC 181954 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0254 PM CDT Thu May 18 2023 Valid 182000Z - 191200Z ....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS TEXAS PANHANDLE VICINITY... ....SUMMARY... Generally isolated severe thunderstorms are expected across parts of the central to southern Great Plains, the Upper Midwest, and the Tennessee Valley this afternoon and evening. Relatively greater potential for severe hail and a tornado or two is apparent over the Texas Panhandle vicinity. ....20Z Update... Minor changes to the general thunderstorm lines were made based on observed trends. The outlook is otherwise unchanged. ...Wendt.. 05/18/2023 ..PREV DISCUSSION... /ISSUED 1127 AM CDT Thu May 18 2023/ ....Southern/central High Plains... Relatively unfocused and generally marginal severe potential is anticipated this afternoon and evening as scattered thunderstorms develop from the Front Range to the Trans-Pecos and spread east. The broad cat 1-MRGL risk covers the bulk of the area with an embedded cat 2-SLGT in the TX Panhandle vicinity where a few supercells are most probable. Mid-level lapse rates should not be particularly steep east of the higher terrain. Weak deep-layer shear is anticipated south of the TX Panhandle, while weak buoyancy will be common north of the Panhandles. As such, the central High Plains portion should tend to favor an isolated/marginal severe hail threat initially, transitioning to more of a locally strong gust threat as storms congeal eastward. Most of the west TX portion should tend to be high-based initially and overall favor strong to locally severe wind gusts. The TX Panhandle vicinity will largely be driven by differential heating surrounding a persistent stratus deck that should slowly erode but may not completely dissipate. 12Z CAM consensus suggests an initial round of discrete cells may form around mid-afternoon, with a more probable later round of higher-based clusters spreading east from the Sangre de Cristos during the early evening. Low-level hodograph curvature should increase during the early evening and become moderately enlarged. These may support a few supercells as effective bulk shear increases to 30-35 kts. This could yield a relatively greater corridor of severe hail potential before storms further consolidate and gradually diminish after sunset. The tornado threat will be conditionally dependent on maintaining a discrete supercell mode during the early evening within the weakly focused baroclinic zone. ....Upper Midwest... A shortwave trough over southern Manitoba will slowly move southeast towards the Twin Ports area tonight. Leading and reinforcing surface cold fronts are expected to push southeast, with the lead one focusing isolated severe potential during the late afternoon to early evening. A plume of around 1 inch PW values characterized by mid to upper 50s surface dew points should be confined along the front and yield a corridor of weak buoyancy from northeast IA/southeast MN into central WI. While the strongest belt of mid-level flow will lag behind the leading front, moderate deep-layer shear will favor a few organized updrafts capable of isolated severe hail and damaging winds. This severe threat is expected to last up to around 3-4 hours due to the narrow instability axis and onset of nocturnal cooling. ....Southeast... Generally weak deep-layer flow will preclude organized convection across the Southeast this afternoon, but sporadic wet microbursts producing locally strong wind gusts will be possible. One area of somewhat more focused downburst and marginally severe hail threat remains apparent ahead of a slowly decaying mid-level trough drifting east from the Mid-South to the TN Valley. Here, relatively colder mid-level temperatures may compensate for the weak shear regime and support a marginal severe threat as scattered thunderstorms form and drift east through south. $$ = = = 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) .