SPC AC 211245
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0745 AM CDT Thu Mar 21 2019
Valid 211300Z - 221200Z
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOUR CORNERS
AREA TO THE TRANS-PECOS OF FAR WEST TX...
Isolated, marginally severe wind gusts and hail are possible in the
early afternoon near the Four Corners and then around early evening
south into the Trans-Pecos of far west Texas.
...Four Corners to the Trans-Pecos...
Primary change is to expand the Marginal Risk south into the
Episodic thunderstorm events are expected through this evening in
association with an upper trough over the Southwest. Convection is
already ongoing owing to forcing for ascent associated with a lead
shortwave impulse over central AZ. This impulse should reach the
Four Corners by mid-afternoon before tracking towards southwest WY,
while an upstream impulse reaches the Lower CO River Valley by
evening. The early timing of the lead impulse will be unfavorable
for substantial destabilization in the Four Corners area. But meager
buoyancy (SBCAPE below 500 J/kg) may develop amid strong 0-3 km
shear to warrant a threat for a marginally severe storm or two.
A secondary corridor of marginal severe storm threat may exist
towards early evening as weak mid-level height falls occur with the
approach of the latter impulse. In conjunction with the opportunity
for recovery in the wake of early morning convection and greater
duration of boundary-layer heating, a confined plume of SBCAPE
around 500 J/kg may develop near the Rio Grande Valley from central
NM into far west TX. Along the southeast periphery of moderate
deep-layer shear, a couple mid-level rotating updrafts may form
capable of marginal severe hail and wind.
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