Severe Storm Outlook Narrative (AC)
Issued by NWS
Issued by NWS
792 ACUS02 KWNS 180541 SWODY2 SPC AC 180540 Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1240 AM CDT Fri Oct 18 2024 Valid 191200Z - 201200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS THE SOUTHERN HIGH PLAINS... ...SUMMARY... Strong to severe thunderstorms are possible across the southern High Plains Saturday into Saturday night. Large hail will be the primary threat, though isolated severe winds and a tornado may also occur with the strongest storms. ...Synopsis... The upper-level trough within the lower Colorado River Valley will become a closed low in the Southwest and become nearly stationary just south of the Four Corners on Saturday. Mid-level winds associated with this feature are expected to weaken some as compared to Friday, though some intensification may occur as the trough becomes more progressive by early Sunday morning. At the surface, modest return flow of generally poor-quality low-level moisture will continue into the southern High Plains as a surface trough is maintained from eastern Colorado into eastern New Mexico. Nebulous ascent from the upper-level low as well as low-level warm advection should promote some showers/thunderstorms early in the period, especially in New Mexico. ...Central/eastern New Mexico into western Texas... Southeasterly return flow around the surface high in the Ohio Valley will maintain mid to upper 50s F dewpoints in the southern High Plains. Forcing from the upper low and a Pacific cold front will promote late-afternoon thunderstorm development from central to eastern New Mexico. Ongoing precipitation early in the period gives some uncertainty as to how much surface-based destabilization will occur. MLCAPE of around 1000 J/kg appears possible where greater heating occurs with closer to 500 J/kg elsewhere. However, there appears a slightly more favorable zone for heating from the Davis Mountains into east-central New Mexico. Deep-layer shear will be favorable for supercells, and mid-level lapse rates will remain steep enough to support some threat for large hail even if some storms remain slightly elevated. Isolated strong to severe gusts could occur with the most organized supercells. Low-level shear will increase after 00Z, but a simultaneous increase in low-level stability is also expected. Even so, a narrow window exists for a tornado or two should a mature supercell persist into the early evening. Given a slightly slower eastward progression of the upper low in recent guidance, a small westward shift in severe probabilities was made. Some guidance shows convection developing within the Davis Mountains. Given the weak synoptic lift and potential for low-level clouds and stable conditions to the east, it is not clear if storms will develop or for how long they can persist eastward into marginally greater moisture. A conditional threat for severe hail would exist if a storm or two can develop and mature in the Trans-Pecos region. ..Wendt.. 10/18/2024 $$