SPC AC 230055
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0755 PM CDT Wed Mar 22 2017
Valid 230100Z - 231200Z
...NO SEVERE THUNDERSTORM AREAS FORECAST...
The risk for severe thunderstorms tonight appears generally
negligible across the U.S., but areas of scattered thunderstorm
activity remain possible, particularly across parts of the
Southwestern deserts into southern Great Basin, portions of the
lower Missouri Valley, and near the Florida Atlantic coast.
...Pacific Coast into Rockies and high Plains...
Upper troughing within the southern branch of split westerlies
emanating from the mid-latitude Pacific is forecast to continue to
progress inland of the California coast, and across the Sierra
Nevada and lower Colorado Valley, tonight. As it does, weak
destabilization associated with a southerly influx of low/mid-level
moisture and large-scale forcing for ascent probably will maintain
scattered thunderstorm activity spreading across much of Arizona and
southern/eastern Utah tonight.
Otherwise, thunderstorm activity elsewhere to the west of the
Rockies appears significantly tied to daytime heating and seems
likely to diminish through the 02-04Z time frame. At the same time,
lower/mid tropospheric warm advection to the east of the Rockies
could maintain isolated to widely scattered thunderstorm activity
across parts of the northern high Plains this evening.
Isolated thunderstorm activity has formed off the higher terrain of
southwest Texas and the adjacent Mexican Plateau region. While the
environment across this region may be marginally conducive to
supercells, it appears that any window of opportunity for
substantive intensification will be short-lived, as
cooling/decoupling of the boundary layer progresses through the
01-02Z time frame.
...Lower Missouri Valley...
Mid-level moistening and destabilization, within a strengthening
zone of lower/mid tropospheric warm advection (east of stronger
mid-level capping associated with elevated mixed layer air now
overspreading the central/southern Plains) may be sufficient to
support scattered weak thunderstorm activity tonight. This could
initiate as early as 05-07Z, but seems more probable in the 09-12Z
Forcing to maintain ongoing thunderstorm activity near Orlando
remains unclear. However, a plume of relatively steep mid-level
lapse rates, associated with elevated mixed layer air emanating from
the Plains, is contributing to considerable potential instability,
and further steepening of lapse rates is possible this evening in
association with mid-level cooling accompanying large-scale
troughing now shifting across/east of the Atlantic seaboard. Aided
by forcing associated with a short wave impulse digging through the
southern portion of this trough, additional thunderstorm activity
appears possible overnight near or just east of east central Florida
coastal areas, where an easterly component to the low-level flow
will focus low-level convergence.
NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0600Z