Severe Storm Outlook Narrative (AC)
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ACUS02 KWNS 281742
SWODY2
SPC AC 281741

Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1241 PM CDT Tue Mar 28 2017

Valid 291200Z - 301200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS WEDNESDAY
AFTERNOON AND NIGHT OVER MUCH OF AR...NORTHWEST LA...EAST TX AND
EXTREME SOUTHEAST OK...

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS SURROUNDING THE
ENHANCED RISK FROM SOUTHEAST KS...SOUTHERN MO...AND SOUTHERN IL TO
THE MIDDLE TX COAST...

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PORTIONS
OF THE SOUTHERN PLAINS TO THE LOWER AND MIDDLE MS VALLEY...

...SUMMARY...
Severe thunderstorms are expected on Wednesday into Wednesday night
from parts of east Texas, eastern Oklahoma, and southeast Kansas
into the lower and middle Mississippi Valley.

...Synopsis...
A strong shortwave trough will move steadily east across the
southern half of the Great Plains on Wednesday into Wednesday night
toward the lower and middle MS Valley, while an embedded closed
midlevel cyclone tracks from northwest TX into OK and KS.  An
upstream shortwave trough is expected to dig southeastward from the
southwest states through northern Mexico toward the lower Rio Grande
Valley late Wednesday night.  At the surface, an elongated area of
low pressure is expected to extend from southwest OK to
south-central/southeast KS at 12Z Wednesday, with models suggesting
low pressure will tend to consolidate and reach southwest MO region
by 12Z Thursday.  A cold front/dryline is forecast to extend
southward through central OK to deep south TX at the start of day 2.
This front will shift slowly east into eastern OK and east TX by
Wednesday afternoon.  A warm front will move north across much of AR
and the Mid-South, reaching southeast KS, southern MO to western TN
by 30/00Z.  A secondary cold front surging to the east/southeast
across the southern Plains should overtake the lead cold front late
Wednesday night and extend from western AR to off the TX coast by
12Z Thursday.

...Southern Plains to lower-mid MS Valley...
Models continue to indicate the widespread thunderstorms across the
southern Plains tonight should diminish in intensity and severe
threat Wednesday morning over east TX, east OK into southeast KS to
southwest MO.  Midlevel impulses translating through the eastern
periphery of the closed low Wednesday morning and afternoon should
support renewed storm development/intensification from parts of
northeast TX through eastern OK to southeast KS along the first cold
front.  Greater destabilization on the northern extent has resulted
in a little northward expansion of the Slight risk area.  Although
strong shear vectors oriented nearly parallel to the cold front
suggest a linear storm mode, the strength of the bulk shear /50+ kt/
and moderate instability support embedded supercells.  Thus, all
severe hazards will be possible, except farther north into northeast
KS where storms should remain elevated.

Meanwhile, the next in a series of midlevel shortwave troughs will
move toward the Ark-La-Tex region Wednesday evening and night, and
strong 500-mb 2-hour height falls of 60-90 meters are expected
across the Ark-La-Tex and eastern OK to the lower and mid MS Valley.
Additional storms will develop across east TX Wednesday afternoon
where the environment will be moderately unstable with strengthening
effective bulk shear resulting in organized storms producing all
severe hazards.  A 50+ southerly low-level jet developing Wednesday
evening and shifting east after dark will increase the severe-
weather threat resulting in a risk of supercells and bowing
structures producing tornadoes (possibly strong), as well as large
hail and damaging winds.

...Middle TX Coast to Deep South TX...
The southern extent of the first cold front is expected to move
offshore Wednesday morning of the middle and southern TX coast,
though moisture return in expected Wednesday night with the approach
of the digging shortwave trough and the approach of the secondary
cold front.  Steep midlevel lapse rates spreading atop the moisture
return will support moderate instability, with a few strong to
severe storms possible late Wednesday night/early Thursday morning
as the cold front reaches the middle and south TX coastal region.

..Peters.. 03/28/2017

$$


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