Severe Storm Outlook Narrative (AC)
Issued by NWS

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000
ACUS01 KWNS 271626
SWODY1
SPC AC 271625

Day 1 Convective Outlook
NWS Storm Prediction Center Norman OK
1125 AM CDT Thu Jul 27 2017

Valid 271630Z - 281200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS EASTERN WY
VICINITY...

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS NORTHERN/CENTRAL
HIGH PLAINS...

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS SOUTHERN
APPALACHIANS TO MID-ATLANTIC...

...SUMMARY...
Scattered large hail and isolated severe wind gusts are expected
late afternoon into this evening in the eastern Wyoming vicinity.
Locally damaging winds are possible this afternoon over the southern
Appalachians and Mid-Atlantic States.

...Northern/central High Plains...
Isolated to scattered storms will develop off the Front Range and
Big Horns late this afternoon with a few supercells likely evolving
in a north/south corridor across the eastern WY vicinity. In this
corridor, surface dew points in the upper 50s to lower 60s are
prevalent with robust insolation underway. This should result in
MLCAPE reaching 1000-1500 J/kg. With approach of a decaying
mid-level impulse from ID maintaining a belt of enhanced high-level
westerlies, effective shear of 30-40 kt will support updraft
rotation. While mid/upper-level lapse rates will not be particularly
steep, they should still be sufficient for a risk of large hail and
locally severe winds.

...Southern Appalachians to Mid-Atlantic States...
Non-severe multicell clusters are ongoing across parts of the
Cumberland to Allegheny Plateau of KY/WV. As pockets of moderate
diabatic heating occur from NC to Delmarva, this activity along with
additional widely scattered storm development may become weakly
organized amid 20-25 kt effective shear. The marginal mid-level
lapse rate environment suggests buoyancy should remain modest.
Primary hazard will be isolated strong wind gusts producing tree
damage.

...OK to OH Valley...
Extensive cloud cover and areas of stratiform rain are ongoing
along/ahead of a frontal boundary extending from northern OK to the
Midwest. This will limit destabilization near the front with
diabatic heating more pronounced farther south within a weak
mid-level lapse rate and shear environment. Sporadic downbursts are
possible where widely scattered pulse storms form late afternoon
into evening, but the risk for organized severe storms appears
minimal.

..Grams/Dial.. 07/27/2017

$$


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