Severe Storm Outlook Narrative (AC)
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000
ACUS02 KWNS 270538
SWODY2
SPC AC 270536

Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1236 AM CDT Thu Apr 27 2017

Valid 281200Z - 291200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM OKLAHOMA
INTO A PORTION OF THE MISSISSIPPI...TENNESSEE AND OHIO VALLEYS...

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM A PORTION OF
THE SOUTHERN PLAINS INTO THE OHIO VALLEY...

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS SURROUNDING THE
SLIGHT RISK AREA...

...SUMMARY...
Numerous severe storms remain possible on Friday from a portion of
the southern Plains into the lower to middle Mississippi, Ohio and
Tennessee Valleys.

...Southern Plains through lower Mississippi and Ohio Valleys...

Embedded within a broad synoptic trough, a lead shortwave trough
initially over the central Plains will deamplify and weaken as it
moves into the Great Lakes area. Farther upstream an upper trough
will amplify near the Four Corners region. At the surface a warm
front will develop northward through north TX and OK eastward into
the OH Valley, while a cold front advances south through the central
Plains. Dryline will evolve across west-central into northwest TX or
southwest OK during the afternoon where it will intersect the
warm/quasi-stationary front.

Height rises will occur from the southern Plains to the TN Valley in
wake of the lead shortwave trough that will move toward the Great
Lakes. Limited synoptic forcing for ascent and convective inhibition
resulting from eastward expansion of the EML should limit
thunderstorm initiation during the day over most of the warm sector.
Some chance for isolated thunderstorm initiation will exist at the
intersection of dryline and front over northwest TX into southwest
OK by late afternoon. Large CAPE and strong vertical shear will
favor a conditional risk for supercells with very large hail and a
few tornadoes should such initiation occur. Rich low-level moisture
with large CAPE but strong convective inhibition will reside south
of the warm/Quasistationary front. The best chance for widespread
thunderstorm initiation will occur during the evening and overnight
from OK into northern AR, MO and into the TN and OH valleys as a
strong, broad low-level jet enhances convergence and isentropic
ascent within the strengthening baroclinic zone. Strong vertical
shear profiles and instability will support organized storms
including supercells with large to very large hail and damaging wind
the main threats, though a few tornadoes may also occur with any
surface-based storms developing closer to the warm front.

..Dial.. 04/27/2017

$$


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