Severe Storm Outlook Narrative (AC)
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000
ACUS03 KWNS 190736
SWODY3
SPC AC 190735

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0135 AM CST Fri Jan 19 2018

Valid 211200Z - 221200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR PORTIONS OF
EAST TX...FAR SOUTHEAST OK AND WESTERN AR...

...SUMMARY...
Isolated severe thunderstorms are possible Sunday afternoon and
evening from east Texas northeastward into western Arkansas.

...Synopsis...
Shortwave trough over the Four Corners region at the beginning of
the period is expected to progress northeastward into the central
Plains while deepening and maturing. Southwesterly winds aloft
preceding the system will strengthen while overspreading the
southern/central Plains and lower/mid MS Valley. Surface reflection
of this system will move quickly northeastward from the TX Panhandle
into the lower MO Valley. Moisture return ahead of this system will
likely result in enough instability to support thunderstorms,
include the potential for a few severe storms (discussed in more
detail below).

Farther northwest, a progressive shortwave trough will move through
the Pacific Northwest during the afternoon/evening. A few lightning
strikes will be possible across the region, particularly after the
initial frontal band as temperatures aloft cool and cellular
convection persists.

...East TX...Far southeast OK...Western AR...
Moisture return is expected to result in dewpoints in the upper 50s
to low 60s from the lower TX coast northward through the Ark-La-Tex.
Daytime heating will be limited by considerable cloudiness,
tempering the development of much surface-based instability. Current
guidance suggests SBCAPE values will remain below 500 J/kg.
Additionally, expected progression of the upper system will result
in a displacement between the strongest forcing for ascent (across
eastern KS and MO) and the best low-level moisture/instability. Even
so, a line of showers and thunderstorms is expected to develop
during the afternoon as the Pacific front/dryline associated with
the system encounters the marginally unstable environment across
east/northeast TX. Continued thunderstorm development is possible
farther north through western AR during the evening.

Strong wind fields will favor fast-moving storms and the potential
for a few strong wind gusts, particularly during the late afternoon
and evening from east TX into western AR where the greatest
potential for surface-based convection exists. Despite strong
forcing for ascent, northern extent of the severe threat will be
limited by meager instability. Farther south, warm temperatures
aloft will likely keep afternoon and evening convection shallow.

..Mosier.. 01/19/2018

$$



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