Severe Storm Outlook Narrative (AC)
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ACUS02 KWNS 250547
SWODY2
SPC AC 250546

Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1246 AM CDT Thu May 25 2017

Valid 261200Z - 271200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF
THE CENTRAL PLAINS...

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE CENTRAL
HIGH PLAINS EAST TO PORTIONS OF THE OHIO VALLEY...

...SUMMARY...
Severe thunderstorms will be possible Friday across the central High
Plains eastward into the middle Mississippi and Ohio Valley region.
The greatest coverage of severe storms will be from northeastern
Colorado into western and central Kansas.

...Synopsis...
An upper-level low over the northeast states will lift northeast
while another upper low over Manitoba/Saskatchewan Provinces moves
little.  Within the relatively low-amplitude flow that will evolve
south of these features, a shortwave trough will move across the
central High Plains late in the day.  A cold front will extend south
from the upper Midwest across Kansas/eastern Colorado Friday
afternoon, while a second cold front extends from the southern High
Plains across Oklahoma to a weak surface low near the
Missouri/Illinois border.  A warm front will extend east from the
low across the Ohio Valley.

...Central Plains...
An increasingly moist southeasterly low-level flow (upper 40s/near
50 deg F surface dew points) will develop across the higher terrain
of northeast Colorado/southeast Wyoming on Friday, with mid/upper
50s farther east across Kansas. This will result in MLCAPE of
750-1500 j/kg by late afternoon, and mid-level flow of 35 kts will
contribute to deep-layer shear of around 40 kts. Thunderstorms
should develop across the high terrain as the upslope flow is
augmented by ascent with the approaching upper-level impulse.
Initial storm mode will include a few supercells capable of very
large hail given steepening mid-level lapse rates. Damaging gusts
will also be possible, and forecast soundings depict low-level
hodograph curvature that suggests at least some risk for a tornado.
A developing 30-35 kt low-level jet/warm advection regime should
result in one or two clusters eventually evolving and moving east
overnight across western/central Kansas. A continued risk for large
hail and strong winds will exist with these storms.

...Missouri east to the Ohio Valley...
Substantial variability exists with latest guidance regarding
thunderstorm development along the frontal boundary across Missouri
Friday afternoon, and potentially just north of the warm front over
the Ohio Valley Friday night. Convective inhibition will likely hold
through much of the day, but frontal convergence may result in
isolated thunderstorm development in the 21z-03z time frame along
the cold front. Strong surface-based buoyancy and 35-40 kts of
deep-layer shear would support severe storms with any sustained
updrafts. Given uncertainty regarding development, will retain the
Marginal Risk with this outlook.

Developing warm advection Friday night and lift with a mid-level
impulse may result in thunderstorm development north of the warm
front. Guidance remains divergent regarding the location of the
front and the potential for development, but believe sufficient
confidence exists to maintain Marginal Risk across portions of the
Ohio Valley. Moderate elevated buoyancy and 45 kts of westerly
mid-level flow would be sufficient for a severe hail and wind risk.

...Southern Plains...
Despite intense diurnal heating, strong capping is expected to
suppress convective development along a dryline extending from
south-central Oklahoma into southwest Texas.

..Bunting.. 05/25/2017

$$



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