Severe Storm Outlook Narrative (AC)
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000
ACUS11 KWNS 140039
SWOMCD
SPC MCD 140038
MNZ000-IAZ000-NEZ000-SDZ000-KSZ000-COZ000-140215-

Mesoscale Discussion 1490
NWS Storm Prediction Center Norman OK
0738 PM CDT Sun Aug 13 2017

Areas affected...Eastern CO...Northwest KS...Southwest and Central
NE...Southeast SD...Southwest MN...Northwest IA

Concerning...Severe Thunderstorm Watch 451...

Valid 140038Z - 140215Z

The severe weather threat for Severe Thunderstorm Watch 451
continues.

SUMMARY...The threat for widely scattered severe thunderstorms will
continue into the evening, with a primary threat of large hail and
damaging wind. A gradual decreasing trend is expected later this
evening.

DISCUSSION...Widely scattered strong-to-severe thunderstorms are
ongoing across WW 451 as of 0015Z. In the short term, the greatest
severe threat will likely exist across central NE with the supercell
cluster over Custer County near Broken Bow, where moderate buoyancy
and effective shear are in place per the 00Z LBF sounding. This
cluster will continue to be capable of large hail (potentially
greater than 2 inches in diameter) and locally damaging wind.

Further north, supercells noted over northeast NE and southeast SD
(west of Sioux Falls) will also continue to pose a localized wind
and hail risk, though buoyancy is somewhat weaker across this area
and very dry midlevel air wrapping into the backside of the vort max
may tend to limit updraft intensity to some extent. To the
southwest, a weaker thunderstorm cluster over eastern CO may have
some potential to intensify as it moves southeastward into a more
unstable environment.

A modest increase in the low-level jet will support some increase in
convective coverage by mid-evening. This may support one or more
upscale growing clusters, which could pose a somewhat greater risk
of damaging wind. Eventually, increasing SBCINH will result in a
decreasing severe threat by late tonight.

..Dean.. 08/14/2017

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

ATTN...WFO...FSD...OAX...GID...LBF...GLD...BOU...

LAT...LON   38830294 39830310 43959789 44029524 42349666 40349883
            38800083 38830294




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