SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0250 PM CDT Tue Sep 19 2023 Valid 192000Z - 201200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS OF OKLAHOMA...THE TEXAS BIG COUNTRY...AND NORTH-CENTRAL TEXAS... ...SUMMARY... Severe thunderstorms capable of large to very hail and damaging gusts are possible today and tonight across portions of Oklahoma and the Texas Big Country into north-central Texas. ...20Z Update... ...Much of OK into TX Big Country and North TX... Warm-air advection showers and thunderstorms continue in an arc from north-central OK into north-central TX. Temperatures immediately west of the this arc are in the low 80s, increasing into the upper 80s and low 90s farther west across western OK and adjacent portions of the TX Panhandle. This warming is expected to continue, fostering further destabilization ahead a subtle shortwave moving across the TX/OK Panhandles. Consequently, as outlined in the previous forecast, re-development is still anticipated across western OK and northwest TX later this afternoon/evening. These storms will then track eastward/northeastward into more of central OK and north-central TX. Moderate northwesterly flow aloft will contribute to 45-50 kt of effective shear, supporting the potential for organized updrafts capable of large to very large hail. Damaging gusts are possible with this activity as well, particularly if upscale growth into a forward-propagating line occurs. ..Mosier.. 09/19/2023 .PREV DISCUSSION... /ISSUED 1110 AM CDT Tue Sep 19 2023/ ...OK/North TX... Morning water vapor imagery loop shows multiple subtle mid-level vorticity maxima moving across the central Plains. The primary system is currently over southwest/south-central KS, and aided in rather widespread convection overnight across OK/KS. The back edge of stronger forcing associated with this feature is over western OK, with clear skies and southerly low-level winds back in place. By mid/late afternoon, strong heating will lead to a corridor of moderate CAPE across western OK into western North TX. A consensus of CAMS develop scattered thunderstorms along this axis, with storms persisting for a few hours and tracking into central OK and north-central TX. Forecast soundings show steep mid-level lapse rates and 40-50 knots of effective shear. This will support supercells capable of very large hail and damaging wind gusts. An isolated tornado or two is also possible. Model guidance is also consistent in developing storms in north-central OK this afternoon, just ahead of the upper system over KS. This area will see less heating/destabilization than farther south, but could also see a cluster of intense storms that move across northeast OK. Damaging winds and hail would be the main threat.
