Valid 222000Z – 231200Z
…THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS THIS
AFTERNOON/EVENING FOR PARTS OF THE CENTRAL/SOUTHERN CA COAST…
Isolated strong storms may produce gusty winds over parts of coastal
central/southern California this afternoon and evening.
No changes were required to the existing Day 1 outlook.
.PREV DISCUSSION… /ISSUED 0125 PM CDT Sun Mar 22 2020/
A largely zonal flow regime persists across the CONUS, with multiple
embedded shortwave troughs (in both a northern and southern stream)
moving generally eastward from the Rockies to the MS Valley. A few
elevated thunderstorms could persist through the day from southern
AL to GA in the zone of ascent preceding a shortwave trough now over
MS/AL. Other widely scattered thunderstorms are expected this
afternoon from the central High Plains into NE. Surface heating and
steep lapse rates will support high-based convection along a surface
trough preceding a shortwave trough moving eastward from CO, but
weak buoyancy will limit any severe threat, despite sufficient
deep-layer shear for organized/supercell storms across western KS.
Overnight, some increase in low-level warm advection is expected
from the lower MS Valley into the TN Valley, where elevated
thunderstorms will be possible in a band immediately north of the
residual baroclinic zone that is now near the Gulf coast.
…Parts of the central/southern CA coast this afternoon/evening…
A closed midlevel low will move inland across the central/southern
CA this afternoon, while gradually evolving into more of an open
wave. Focused ascent in the left-exit region of the mid-upper jet
combined with steepening lapse rates below 500 mb will result in a
threat for a broken arc of showers/thunderstorms along the coast
this afternoon/evening. Buoyancy will likely remain weak, but
veering low-level winds and substantial speed shear aloft will be
sufficient for some embedded/organized storms with an accompanying
threat for isolated damaging gusts and small hail.