Severe Storm Outlook Narrative (AC)
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ACUS01 KWNS 200528
SWODY1
SPC AC 200527

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1127 PM CST Mon Feb 19 2018

Valid 201200Z - 211200Z

...NO SEVERE THUNDERSTORM AREAS FORECAST...

...SUMMARY...
Thunderstorms are expected from Texas to the Great Lakes today into
tonight. While a stronger storm or two may occur from the Arklatex
to the Ozarks, organized severe weather is not currently expected.

...Synopsis...
The large-scale mid/upper pattern will remain relatively unchanged
today, as the center of a strong ridge persists offshore the
Southeast US and a deep trough encompasses much of the western US.
Between the two, a broad corridor of strong mid-level
southwesterlies will exist from the Desert Southwest northeastward
to the upper Midwest. Within this regime, an elongated, diminishing
vorticity maximum will advance across the southern Plains, while
multiple weak, convectively augmented impulses eject north/northeast
in advance of this vorticity max. At the surface, a cold front will
accelerate southeastward across the southern Plains and mid
Mississippi Valley.

...Arklatex to the Ozarks...
Weak mid/upper ascent will approach the region during the afternoon
and evening hours. As it does so, a persistent low-level jet and
related convergence near/ahead of the advancing front are forecast
to foster an increase in convection. Heating will be limited during
the day, but northward moisture return should support upwards of 500
J/kg of MLCAPE by late afternoon. Aided by this buoyancy, shallow
thunderstorms should organize from northeast Texas to southern
Missouri through the evening hours. Forecast soundings suggest
low-level shear may be favorable for a localized wind/tornado threat
with any cells/segments ahead of the front. However, convection may
struggle to stay firmly rooted in the surface warm sector ahead of
the front, considering south/southwesterly cloud-layer flow, weak
buoyancy, and the southeastward push of the front. Therefore, have
opted against introducing marginal probabilities at this time,
although they could be added in later updates.

..Picca/Jirak.. 02/20/2018

$$



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