SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1224 AM CDT Sun Oct 16 2022 Valid 161200Z - 171200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS SOUTHEAST NEW MEXICO INTO SOUTHWEST TEXAS AND ACROSS THE SOUTHERN APPALACHIANS... ...SUMMARY... Several thunderstorms, accompanied by an isolated severe hail/wind risk, are expected across southeastern New Mexico into southwest Texas this afternoon and evening. Isolated strong to severe storms capable of damaging winds are also possible across parts of the southern Appalachians. ...Synopsis... An upper-level low over northern Baja California will continue to drift east over the next 24 hours. The approach of this wave will yield broad ascent across southeast NM and southwest TX as well as establish a broad west/southwesterly flow regime aloft. Weak surface pressure falls are expected across southwest TX in response to the evolving upper-level regime and will maintain a flux of low-level moisture from south-central TX. Meanwhile, a surface cold front loosely draped from the Midwest into the southern Plains will continue to migrate south/southeast through the day into the southern Appalachians, mid-MS River Valley, and into southwest TX. Thunderstorm development is expected along this boundary with the greatest convective coverage across the southern High Plains where forcing for ascent will be greatest. ...Southeast New Mexico to Southern Texas... Isolated to scattered showers and thunderstorms may be ongoing early this morning across southeast NM/southwest TX, but will gradually increase in coverage and intensity through the day as diurnal warming and cooling temperatures aloft bolster instability to near 1000-1500 J/kg MLCAPE. Strengthening flow aloft overlaid with persistent southeasterly low-level winds will yield elongated hodographs with effective shear values near 40-50 knots. The thermodynamic/kinematic environment will be conducive for organized convection, including a few supercells, capable of large hail and severe winds within the warm conveyor regime ahead of the low. However, storms may be undercut as a cold front pushes to the south through the afternoon. This may limit the spatial/temporal range of the threat to some degree for southeast NM and portions of southwest TX. The best potential for persistent organized convection will likely reside across the Big Bend region and along the Rio Grande in south-central TX, which will see locally augmented lift off the Chisos and Sierra del Carmen mountains, and experience the longest maintenance of a favorable environment prior to the frontal passage. Consideration was given for upgraded wind/hail probabilities for this region, but limited confidence in the spatial threat on the U.S. side of the border precluded an upgrade. ...Southern Appalachians... Southwesterly low-level flow through the day will foster modest moisture return into the southern Appalachian region with dewpoints climbing to the upper 50s/low 60s. The combination of improving boundary-layer moisture and lift along the boundary will promote thunderstorm development by late afternoon. Strong flow within the base of the synoptic trough will support elongated hodographs with 0-6 km bulk shear vectors near 30-50 knots; however, poor mid-level lapse rates (sampled by regional 00 UTC soundings) will limit overall buoyancy profiles and modulate updraft intensity. A few organized cells are possible and may pose a damaging wind threat, especially with 30-40 knot flow expected near the top of the mixed boundary layer by late afternoon. ..Moore/Broyles.. 10/16/2022
