Severe Storm Outlook Narrative (AC)
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572
ACUS02 KWNS 280557
SWODY2
SPC AC 280556

Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1256 AM CDT Wed Jun 28 2017

Valid 291200Z - 301200Z

...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS EASTERN
NE AND KS...SOUTHWEST IA...AND NORTHWEST MO...

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS ACROSS MUCH OF NE
AND KS AND EXTENDING EASTWARD TOWARD THE LOWER GREAT LAKES....

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE CENTRAL
HIGH PLAINS EASWARD INTO UPSTATE NY...

...SUMMARY...
Scattered significant severe thunderstorms are most likely Thursday
across the central Plains, with areas of hail and damaging wind.
Isolated strong storms are also possible across the Midwest eastward
into western Pennsylvania and New York with localized severe wind
gusts.

...Synopsis...
A shortwave trough will move from the central Rockies Thu morning to
the lower MO Valley by Fri morning, with relatively strong flow
aloft for the time of year. At the surface, a diffuse boundary
(possibly aided by storm outflow) will extend from the upper MS
Valley southwestward into KS, with eventual deepening of a low over
KS later in the day. Moderate instability will develop across much
of the central Plains, which when combined with strengthening wind
fields aloft, will result in severe storms most numerous from NE/KS
into IA and northern MO.

...Central Plains...
Early day storms are expected to be ongoing from eastern NE into
northern IL, near the trailing front extending from the upper Great
Lakes low. Some marginal hail risk may exist Thu morning, as lapse
rates aloft will be steep, and storms may be elevated.

Capping will be eroded near the stationary front by around 21Z from
near the KS/NE border into IA as the moist boundary layer deepens.
Indications are that numerous storms could form in this region, and
this would also suggest some MCS potential. Conditionally, a few
early supercells are possible given the increasing low-level jet and
increasing cyclonic flow aloft. Activity could form a bit earlier
across northern MO or IA if early storms produce any substantial
outflow boundaries.

To the west, strong heating will occur from central NE/KS westward,
with low pressure developing over central KS. Here, low-level
convergence will be on the increase, with a cold front eventually
overtaking the area late in the day. Models such as the NAM show
initial development over eastern CO or western KS where MUCAPE will
be marginal but lapse rates very steep. This suggests an eventual
MCS developing with damaging winds during the evening.

...Midwest into western PA and NY...
Southwesterly 850 mb flow in excess of 30 kt will help transport
moisture toward the lower Great Lakes by late afternoon, with a warm
front lifting northeast across western NY. Midlevel winds will be
relatively strong, on the order of 40-50 kt, which will favor
forward-propagating storms capable of gusty winds. The most
favorable area for severe storms is likely to be coincident with the
strongest instability which will extend from IL/IN toward Lake Erie,
with storms moving mostly in an eastward direction.

..Jewell.. 06/28/2017

$$



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