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Severe Storm Outlook Narrative (AC)
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960
ACUS11 KWNS 272004
SWOMCD
SPC MCD 272004
NEZ000-SDZ000-WYZ000-272230-

Mesoscale Discussion 1163
NWS Storm Prediction Center Norman OK
0304 PM CDT Tue Jun 27 2017

Areas affected...Eastern WY...Western SD...NE Panhandle

Concerning...Severe potential...Watch possible

Valid 272004Z - 272230Z

Probability of Watch Issuance...60 percent

SUMMARY...The area is being monitored for an increase in storm
coverage. Watch issuance is possible later this afternoon, with a
primary threat of large hail and damaging wind.

DISCUSSION...Thunderstorms have recently intensified across
southeast WY, with cumulus development noted further north near DGW,
and additional storm development noted upstream across
central/western WY. The environment across the MCD area is
characterized by a very warm/well-mixed boundary layer and very
steep midlevel lapse rates. Moisture is rather sparse across
portions of eastern WY and increases further east into the NE
Panhandle into western SD, resulting in a range in SBCAPE of
500-2000 J/kg from west to east. Moderate westerly flow in advance
of a compact vort max moving into western/central WY is resulting in
effective shear of 30-40 kt, which will support the potential for
organization with the strongest updrafts.

Some uncertainty remains in the short term regarding storm coverage,
given some remnant SBCINH across the central and eastern portions of
the MCD area. However, continued heating will weaken the cap
strength with time, and some severe threat will likely persist with
the cells moving into the NE Panhandle. With time, with the approach
of the vort max from the west, convective coverage is expected to
increase, with a mixed mode of discrete rotating cells and
larger-scale line segments possible. Steep midlevel lapse rates will
favor a hail risk with any discrete cells, while some damaging wind
threat will evolve with time as cold pools begin to consolidate.
Watch issuance is possible sometime later this afternoon to cover
these threats, though the timing of any watch remains uncertain.

..Dean/Guyer.. 06/27/2017

...Please see www.spc.noaa.gov for graphic product...

ATTN...WFO...LBF...UNR...CYS...

LAT...LON   41060493 41470550 42080596 43910598 44890444 44870279
            44800268 43830208 42190204 41050216 41060493

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