Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Tue Feb 28 2023 12:53:11 ACUS01 KWNS 281253 SWODY1 SPC AC 281251 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0651 AM CST Tue Feb 28 2023 Valid 281300Z - 011200Z ....NO SEVERE THUNDERSTORM AREAS FORECAST... ....SUMMARY... Severe-thudnerstorm potential appears minimal through the period. ....Synopsis... Mid/upper-level mean troughing and associated cyclonic flow will continue over the West, traversed by a series of perturbations of varying magnitudes. A shortwave trough -- apparent in moisture- channel and composited radar imagery over UT -- is expected to eject east-northeastward to eastern WY by 00Z, reaching the SD/MN border around the end of the period. Upstream, a larger trough is evident from the central coast of BC south-southeastward just offshore WA, to coastal northwestern CA. This trough should move southeastward and amplify, resulting in a closed 500-mb low over northeastern CA or northwestern NV by 12Z tomorrow, along a trough from ID to southern CA. Associated strong midlevel cooling and steepened lapse rates will overlie enough low-level moisture to support isolated thunder potential over portions of the Pacific Coast States and northern Great Basin. The surface analysis at 11Z showed a quasistationary front from southern SC to south-central MS and Southeast TX, becoming a slow- moving warm front across south TX to near LRD. By 00Z, this frontal zone will become weaker and warm along its inland length over the Southeast, lower Mississippi Valley and TX, while a low develops near RAP ahead of the shortwave trough. Warm frontogenesis is expected from that low southeastward over east-central NE to near MCI and BNA. By 12Z, the low should reach the MN/SD border area near BKX, with warm/occluded front to parts of IA, IL, IN and OH, and cold front over parts of IA, northern MO, eastern KS to northwest TX and the South Plains. ....Central/north-central TX... A gradual increase in low-level moisture above a relatively stable boundary layer will contribute to potential for elevated thunderstorms to develop the last couple hours of the period over parts of central/north-central TX. Timing of convective initiation is uncertain, but an increasing consensus of guidance and forecast soundings indicates sufficient moistening and cap weakening in the 800-900-mb layer to support essentially uninhibited MUCAPE approaching 1500 J/kg by 12Z over the area. While current indications are that most or all of the severe-hail potential should hold off until day 2 (after 12Z), isolated hail near severe limits cannot be ruled out before that in maturing convection. ....Northern Plains... Isolated to widely scattered thunderstorms are possible this afternoon into the overnight period. Though surface temperatures will be cool, and dewpoints generally in the 20s F, very cold temperatures aloft (e.g., -28 to -30 deg C at 500 mb) preceding the UT-WY perturbation will steepen low/middle-level lapse rates considerably, to at least 8 deg C/km. In the western, diurnal part of the introduced northern Plains thunder area, MLCAPE up to about 200 J/kg is possible -- deep, but with meager CAPE density. The strongest mid/upper winds and mass response to the perturbation should be south of the area of precip. As such, while locally strong convective gusts are possible, low-level winds and effective shear will be weak, and severe potential appears too isolated and conditional for an outlook area. ...Edwards/Kerr.. 02/28/2023 $$ = = = 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) .