Severe Storm Outlook Narrative (AC)
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ACUS03 KWNS 091630
SPC AC 091630

Day 3 Convective Outlook RESENT 1
NWS Storm Prediction Center Norman OK
1030 AM CST Fri Dec 09 2016

Valid 111200Z - 121200Z


Thunderstorms may occur across parts of the lower and mid
Mississippi and Ohio Valleys Sunday.  Showers and a few/occasional
lightning strikes may also occur over portions of the coastal
Pacific Northwest.

While solutions continue to differ -- both between the various
models and also from run to run within the same model, some
amplification of the upper flow field across the U.S. appears likely
to occur Sunday, as short-wave troughing embedded in the
fast/cyclonic westerlies moves quickly out of the Rockies and across
the north-central portion of the country.  As this occurs,
cyclogenesis is forecast as a lee low -- initially over the central
high Plains vicinity -- moves northeastward toward the Ohio
Valley/upper Great Lakes while deepening.  A trailing cold front is
forecast to shift southeastward across the southern Plains and
mid-Mississippi Valley overnight.

...mid and lower Mississippi/Ohio Valleys...
While warm-sector thunderstorms appear unlikely at this time across
the Sabine River Valley area of east Texas and western Louisiana
during the day, isentropic ascent/warm advection atop a cool
continental boundary layer will occur ahead of the developing
surface low and associated frontal system on Sunday.  Moistening
aloft is expected to result in eventual elevated destabilization
sufficient for development of showers and scattered thunderstorms --
from roughly the mid Mississippi to the mid Ohio Valleys.  While
uncertainty remains regarding pattern evolution, and thus details of
convective potential, thunder risk apparent at this time warrants
inclusion of a 10% area, but with destabilization likely
insufficient to support appreciable hail potential.

...coastal Pacific Northwest...
Fast west-northwesterly upslope flow in the lower and middle
troposphere combined with a pocket of cold mid-level air (-34 C at
500 mb) spreading across the area will support showers -- and
occasional lightning -- across coastal mountain ranges of WA and OR
Sunday.  Lack of sufficient CAPE for robust updrafts will preclude
any appreciable severe risk.

...southeast U.S. coastal areas...
Scattered showers, and possibly a couple of thunderstorms, may occur
across FL through the day, and could spread northward into the
coastal Carolinas overnight.

..Goss.. 12/09/2016

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