Severe Storm Outlook Narrative (AC)
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000
ACUS01 KWNS 281600
SWODY1
SPC AC 281558

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1058 AM CDT Sun May 28 2017

Valid 281630Z - 291200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PARTS OF
TX/LA...

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM PARTS OF
LOWER MI/IN/OH INTO THE CAROLINAS...

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE
SOUTHERN PLAINS INTO THE GREAT LAKES...OHIO VALLEY...AND
CAROLINAS...

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER PARTS OF
THE NORTHERN HIGH PLAINS...

...SUMMARY...
Severe thunderstorms capable of large hail and damaging winds will
be possible this afternoon and tonight over portions of
southern/central Texas northeastward into Louisiana.  Other severe
storms may occur over parts of the upper Ohio Valley, central
Appalachians, and Carolinas.

...TX/LA...
After a very convectively active Saturday, the reservoir of extreme
CAPE values is now restricted to portions of TX/LA.  Dewpoints in
the 70s and strong daytime heating will yield a corridor of 4000+
J/kg CAPE by mid/late afternoon across central and northeast TX,
into western LA.  12z model solutions are consistent in the
development of scattered thunderstorms along this corridor - mainly
focused along a weak surface boundary evident in observations and
satellite imagery.  Low-level shear is rather weak in this area, and
deep-layer effective shear is marginal for supercell structures.
Nevertheless, slow-moving severe multicell to occasional supercell
storms are expected with a risk of large hail and damaging winds.
This threat will last through most of the evening hours.

...IN/OH/Lower MI...
A progressive mid-level shortwave trough is currently moving
eastward across WI, and will affect the central Great Lakes region
later today.  Scattered thunderstorms are forecast to develop from
western Lower MI into northern IN by mid afternoon, with other
storms building eastward along a weak warm front into northern OH.
CAPE/shear combinations are not particularly strong in this region,
but cool temperatures aloft and the approaching shortwave trough may
be sufficient for a few severe storms capable of hail and damaging
winds.  The activity may develop eastward into western PA and
northern WV before weakening.

...VA/NC...
Visible satellite imagery shows strong heating is occurring over
much of NC and south-central VA this morning.  Ample low level
moisture remains in place across this area, leading to a moderately
unstable air mass later today.  Scattered thunderstorms are expected
to develop during the max heating period, with a few of the storms
posing a risk of damaging wind gusts and perhaps hail.

...WY/SD/NE...
Scattered thunderstorms will develop later this afternoon and early
evening within a northwest flow regime over the Black Hills and
surrounding region.  Steep mid-level lapse rates and sufficient CAPE
suggest some risk of hail and gusty winds in the stronger cells.

..Hart/Cook.. 05/28/2017

$$


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