SPC 2000Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0239 PM CDT Fri Apr 21 2023 Valid 212000Z - 221200Z ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FOR DEEP SOUTH TEXAS THROUGH EARLY THIS EVENING... ...SUMMARY... Isolated severe thunderstorms will be possible today across parts of south Texas, the lower Mississippi Valley region and upper Ohio Valley/lower Great Lakes. Very large hail is possible over Deep South Texas. ...Discussion... No appreciable change was made to the previous convective outlook. ..Smith.. 04/21/2023 .PREV DISCUSSION... /ISSUED 1112 AM CDT Fri Apr 21 2023/ ...South TX... Strong heating is occurring today over south TX, where dewpoints are in the 70s and afternoon MLCAPE values are forecast to exceed 3500 J/kg. Most CAM guidance shows scattered supercell storms developing across this region by late afternoon. Forecast soundings indicate steep mid-level lapse rates and favorable deep-layer shear, supportive of very large hail potential. Low-level winds are forecast to be rather weak, suggesting the tornado threat is not particularly high. ...ArkLaMiss Region... A decaying MCS is moving southeastward into the central Gulf of Mexico. Clouds associated with this feature are dissipating over much of east TX/AR/LA, allowing partial afternoon heating/destabilization. Dewpoints remain in the mid 60s, which should result in pockets of afternoon MLCAPE of 1000-1500 J/kg. Scattered afternoon thunderstorms are expected to form as a weak cold front sags into this region. While the overall setup in this region is not very robust, a few of the stronger cells could occasionally pose a risk of hail or damaging wind gusts through the early evening. ...Upper OH Valley... A surface cold front is tracking eastward across western OH. Thinning clouds ahead of the front will lead to steep low-level lapse rates and marginal surface-based CAPE by mid-afternoon. Strong winds aloft and forcing along/ahead of the front will result in rather fast-moving showers and thunderstorms capable of gusty winds. Present indications are that limited low-level moisture will result in isolated coverage of stronger cells, so will maintain the ongoing MRGL risk and re-consider an upgrade at 20z.
