Severe Storm Outlook Narrative (AC)
Issued by NWS
Issued by NWS
919 ACUS03 KWNS 190730 SWODY3 SPC AC 190729 Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0229 AM CDT Thu Sep 19 2024 Valid 211200Z - 221200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS IN THE SOUTHERN HIGH PLAINS... ...SUMMARY... Isolated severe thunderstorms are possible on Saturday afternoon to early evening in the southern High Plains. ...Southern High Plains... In advance of a southern-stream shortwave trough reaching the Four Corners, a 50-65 kt 500-mb jetlet is forecast to eject over NM by early evening Saturday. This will yield favorable deep-layer shear for organized storms across eastern NM into parts of northwest TX. Strengthening large-scale ascent within a low-level warm/moist conveyor should overspread this region by Saturday morning. This should yield early-period convection and renders moderate uncertainty over the degree of destabilization by afternoon. Still, with ample boundary-layer heating to the south of early-day activity, a plume of at least weak-surface based buoyancy should develop. Renewed afternoon to early evening thunderstorms should be capable of producing at least isolated severe. Steep mid-level lapse rates should be confined along and west of the Sangre de Cristo Mountains, rendering further uncertainty over the intensity and coverage of the severe threat. The eastern extent of the threat should be curtailed by the confined buoyancy plume and decreasing instability deeper into TX/OK. ...Lower/Mid-MO Valley to the Upper MS Valley... A relatively complex and uncertain evolution to convective potential is evident on Saturday afternoon and evening. This region will largely remain within a low-amplitude mid-level ridge. This may flatten somewhat in between a southern-stream shortwave trough in the Southwest and a northern-stream trough over the southern Prairie Provinces to along the ND/MN international border. In association with the latter wave, a surface cold front should push southeast in the north-central states. Guidance varies with the degree of destabilization ahead of it, and especially with the spatial extent of afternoon/evening convection. As such, a severe threat area has not yet been delineated but may be warranted in later outlooks if predictability increases. ..Grams.. 09/19/2024 $$