Severe Storm Outlook Narrative (AC)
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ACUS02 KWNS 101812
SPC AC 101811

Day 2 Convective Outlook CORR 1
NWS Storm Prediction Center Norman OK
1211 PM CST Sat Dec 10 2016

Valid 111200Z - 121200Z



Thunderstorms will be possible across parts of the lower Mississippi
Valley to western Tennessee Sunday night.  Showers and a few
lightning strikes may also occur over portions of the coastal
Pacific Northwest.

As forecast for several days, the models indicate low-amplitude
cyclonic flow aloft across the contiguous United States through the
day 2/Sunday forecast period.  An embedded shortwave trough should
move through the Upper Midwest to Great Lakes.  Meanwhile, a weak
and sheared impulse should track quickly east, and potentially in
tandem with the Upper Midwest trough, through the southern Plains
and Ozarks region by late Sunday afternoon into the Tennessee Valley
Sunday night.

At the surface, an area of low pressure will develop through the
upper Mississippi Valley into the upper Great Lakes, while the
trailing cold front advances east and southeast through the Midwest,
mid-Mississippi Valley, Ozarks, and the southern Plains.

...Lower Mississippi Valley to western Tennessee...
Strong southwesterly low-level jet, attendant to the progressive
Upper Midwest shortwave trough, is expected to shift from eastern
portions of the southern Plains Sunday morning into the lower
Tennessee and Ohio Valleys Sunday afternoon.  The southern extent of
this low-level flow will allow moisture to return to the north-
northeast ahead of the cold front into the Ark-La-Tex region to
western Mississippi.  The eastern extent of an elevated-mixed-layer
spreading east into this region will inhibit deep-moist convection
from developing until Sunday night.  At that time, greater forcing
for ascent attendant to the southern Plains impulse and within the
frontal zone should allow for elevated storms.  While hail cannot be
ruled out, weak elevated instability and weak effective bulk shear
suggest the probability for hail exceeding 1 inch in diameter will
remain less than 5 percent.

Farther north, much weaker instability should preclude thunderstorm
development into the Ohio Valley Sunday night.

...Pacific Northwest coastal areas...
Cold air aloft located north of a strong westerly 500-mb jet
extending through OR to the northern Great Basin suggests showers
and occasional lightning strikes will be possible from coastal areas
to along the windward slopes of the higher terrain of western
WA/western OR.

..Peters.. 12/10/2016

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