Severe Storm Outlook Narrative (AC)
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ACUS03 KWNS 230828
SWODY3
SPC AC 230828

Day 3 Convective Outlook
NWS Storm Prediction Center Norman OK
0228 AM CST Thu Feb 23 2017

Valid 251200Z - 261200Z

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FOR A LARGE PART
OF VIRGINIA AND THE DELMARVA NORTHWARD INTO NEW
JERSEY...PENNSYLVANIA...AND WESTERN NEW YORK...

...SUMMARY...
Thunderstorms potentially capable of isolated damaging winds are
possible from the Mid-Atlantic states northward through western New
York on Saturday.

...Synopsis...
A very strong and negatively tilted shortwave trough is forecast to
move from the central Great Lakes and Upper Ohio Valley through the
Mid-Atlantic states and much of the Northeast Saturday and Saturday
night.  An occluded surface low will develop northeastward from
northern Michigan into northern Quebec while a cold front pushes
eastward and southeastward across the Northeast through the
Southeast and into the western Atlantic.  Farther west, a mid-level
low/shortwave trough will move southward along the CA coast and into
the Mojave Desert.

...Mid-Atlantic states and western NY...
A squall line or convective line will likely be ongoing Saturday
morning over the central Appalachians northward into western
portions of PA/NY.  Very strong lower-tropospheric wind fields (60
kt at 700-mb) and weak buoyancy (100-500 J/kg MUCAPE) that can aid
in sustaining a squall line may result in a scenario with
quasi-horizontal momentum transport in the form of isolated damaging
gusts.  Farther south near the Mason-Dixon line, models indicate
greater destabilization may occur during the day as a convective
line reinvigorates or new storms develop within a low CAPE/high
shear environment. The strong forcing for ascent (i.e., 500-mb 12-hr
height falls 90-150 m) will likely aid in sustaining this activity
as it moves eastward to the coast and perhaps maintains a
strong/severe risk, primarily in the form of damaging gusts, to
DelMarVa and the New Jersey coast.

..Smith.. 02/23/2017

$$



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