Day 1 Severe Weather Outlook

Valid 011300Z – 021200Z


A few thunderstorms are expected this evening into tonight across
the Mississippi Valley into the lower Ohio Valley. Isolated
thunderstorms may also occur this afternoon/evening across western
Colorado and the higher terrain of southern California.

A split flow regime is in place across the CONUS, with the primary
shortwave troughs moving from ND/MN to Lake Superior in the northern
stream, and southward along the CA coast in the southern stream.
Other more subtle speed maxima are embedded in the southern stream
and will move from NM/OK to the MS Valley overnight. In association
with the northern stream trough, a surface cold front will move
southeastward and be aligned from the I-44 corridor in OK/MO to
Lower MI by 02/12z.

South of the cold front, northward return of a modifying Gulf air
mass is underway, with boundary-layer dewpoints in the upper 50s to
lower 60s along the TX coast this morning. This moisture will
spread north-northeastward toward AR at the surface, and the more
substantial moistening will be above the surface farther northeast.
Above the moistening boundary layer, steep midlevel lapse rates will
spread eastward from OK toward AR. Convective inhibition will be
weaker along the northeast edge of the steeper lapse rates into
AR/MO this evening, when convective initiation is expected in the
warm advection regime from eastern AR into southeastern MO, and
along the front from central MO into central IL. Convection will
spread east-northeastward overnight. Since the more probable area
for storm initiation will be east of the steeper lapse rate plume,
and there will be a weakness in the 700-500 mb flow, will opt to not
add any large hail probabilities across eastern AR/southeastern MO.

Farther west, isolated thunderstorms will be possible across the
higher terrain of southern CA as the developing closed low moves
southward just offshore. However, buoyancy will likely remain weak
inland, and storm coverage will remain isolated at best.

..Thompson/Jewell.. 03/01/2020


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