Severe Storm Outlook Narrative (AC)
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000
ACUS02 KWNS 260437
SWODY2
SPC AC 260436

Day 2 Convective Outlook
NWS Storm Prediction Center Norman OK
1136 PM CDT Sun Jun 25 2017

Valid 271200Z - 281200Z

...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS FROM WESTERN INTO
CENTRAL NEBRASKA AND SOUTH DAKOTA...

...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM YELLOWSTONE
N.P. EASTWARD INTO THE NORTHERN PLAINS AND INTO PARTS OF THE CENTRAL
HIGH PLAINS...

...SUMMARY...
Areas of severe thunderstorms capable of large hail and damaging
wind are expected over much of central and western Nebraska as well
as South Dakota during the late afternoon and evening on Tuesday.
Isolated severe storms are also possible from eastern Colorado into
central Kansas, and from Yellowstone N.P. into North Dakota.

...Synopsis...
A low pressure trough will deepen over the northern and central High
Plains with southerly surface winds bringing 50s to lower 60s
dewpoints as far north as SD by 00Z. By late in the day, shortwave
ridging will give way to height falls as a shortwave trough moves
eastward across WY and MT, with storms forming near the wind shift
and eventually along the cold front. A southerly low-level jet will
strengthen to around 50 kt during the evening ahead of this activity
which will maintain favorable shear profiles and moisture transport.


To the east, cold temperatures aloft will exist courtesy of a large
upper trough over the Northeast, with areas of thunderstorms
possibly producing small hail into New England.

Elsewhere, sporadic afternoon thunderstorms are possible from TX to
FL near a stalled front.

...Western into central SD and NE...
Storms are expected to form by 21Z from near the Black Hills
southward into CO where strong heating will exist and near the low
pressure trough/wind shift. Storms will move into a slightly capped,
but more unstable air mass farther east, where wind profiles will
support supercells. Moderate levels of instability and steep lapse
rates aloft will further support very large hail. Storms are
expected to merge into one or more MCS`s during the evening, with
damaging winds possible. Capping will eventually become a concern,
and will limit the eastward progression of the stronger storms into
Wed morning.

...Yellowstone N.P. area eastward to the Black Hills...
A shortwave trough will move over western areas during the day, with
cooling aloft and daytime heating making the most of minimal
moisture content to produce sufficient instability for a few strong
storms. Storms are expected to form relatively early, between 18-21Z
around the Yellowstone area, and then continue eastward across
southern MT and northern WY during the evening. Locally severe hail
or wind will be possible.

..Jewell.. 06/26/2017

$$



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