12AM Day 1 Convective Outlook for Tuesday, October 14. THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS THE SOUTHERN ROCKIES AND ALONG THE SOUTHERN CALIFORNIA COAST
SUMMARY
Thunderstorms with marginally severe wind gusts and hail are possible across parts of the southern Rockies from late afternoon into the evening. An isolated tornado and wind-damage threat will be possible this morning through midday along the southern California coast.
Southern CA and the Southern Rockies
Upper low continues digging south just off the CA coast, in line with latest model guidance. As midlevel speed max rounds the base of the trough early in the period the upper low will advance inland, then shift into the Great Basin by 15/12z. Weak frontal convection has developed ahead of this feature along the cold front. While most updrafts are too shallow to generate lightning, some risk for isolated thunderstorms is expected as the front surges inland at the start of the period. Left-exit region of the speed max should aid this activity, and some risk for wind damage and perhaps a brief weak tornado can be expected with this frontal convection. Convective threat will decrease quickly across the lower CO River Valley.
Downstream, upper anticyclone is stubbornly holding across the southern Plains into northeast Mexico. This feature will ensure favorable trajectories for maintaining seasonally high PW values across northern Mexico into the southern Rockies. While this higher moisture content necessitates weaker lapse rates across this region, CINH will remain low and even modest boundary-layer heating will lead to adequate instability for robust updrafts. Forecast soundings exhibit 1000-1500 J/kg MLCAPE by late afternoon as surface temperatures warm through the mid 70s to near 80F. Additionally, deep-layer shear should support the potential for organized updrafts, and a few supercells will likely evolve. At this time will maintain MRGL risk for hail/wind with this activity, but later outlooks could reflect higher probabilities if confidence increases regarding the coverage/intensity of convection.