SPC AC 191940
Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
0140 PM CST Thu Jan 19 2017
Valid 192000Z - 201200Z
...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS LATE THIS
AFTERNOON AND EVENING ACROSS PARTS OF FAR SOUTHEASTERN
LOUISIANA/MISSISSIPPI...SOUTHERN ALABAMA AND THE WESTERN FLORIDA
...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS
SURROUNDING PORTIONS OF THE EASTERN GULF STATES...
An evolving cluster of thunderstorms may be accompanied by a risk
for potentially damaging wind gusts, and perhaps a tornado or two,
particularly across southeastern Alabama and portions of the western
Florida Panhandle by late this evening.
...20Z Outlook Update...
Based on latest observational data and model output, potentially
cool/stable near surface air may remain entrenched near/just south
of the higher terrain of northern Georgia into northeastern Alabama.
However, increasing insolation and low-level moistening appear to be
contributing to at least weak boundary layer destabilization to the
south, ahead of slowly strengthening thunderstorm activity on the
leading edge of convective outflow. This boundary has progressed
into western Alabama/far southeastern Mississippi and Louisiana, and
is expected to gradually advance eastward through early evening.
Aided by strengthening large-scale ascent associated the lower/mid
tropospheric warm advection, beneath increasingly difluent and
divergent upper flow, the evolution of an intensifying and
increasingly organized mesoscale convective system appears possible
by early evening. Latest model guidance, including the Rapid
Refresh and ECMWF, suggests that a 850-700 mb speed maximum (40-60+
kt) associated with this feature may develop inland across coastal
areas, through southeastern Alabama, by 03-06Z. It seems probable
that this will be accompanied by the risk for potentially damaging
surface gusts, which could continue into parts of west central and
southwestern Georgia overnight.
.PREV DISCUSSION... /ISSUED 1030 AM CST Thu Jan 19 2017/
...Portions of LA/MS/AL and the FL Panhandle...
While considerable cloud cover persists over much of
central/northern portions of MS into AL, modest
moisture/destabilization could allow for a low-end isolated damaging
wind and/or brief tornado risk through the afternoon/early evening.
Farther south, a somewhat more focused severe risk may exist along
the immediate Gulf Coast this afternoon into this evening, including
parts of southeast Louisiana to far southern portions of MS/AL and
the FL panhandle. While existing cloud cover and ongoing inland
convection cast some uncertainty regarding the effective northward
extent of appreciable destabilization inland, considerable mass
response should occur in tandem with an amplifying upstream trough
over the southern Plains to ARKLATEX. Accordingly, as gradual/modest
destabilization occurs especially immediately near the coast,
increasing forcing for ascent and strengthening deep-layer/low-level
winds could support semi-organized storms modes near the coast later
this afternoon into tonight. At least a localized damaging wind and
a brief tornado threat will exist in these areas.
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