Severe Storm Outlook Narrative (AC)
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000
ACUS11 KWNS 271808
SWOMCD
SPC MCD 271808
MTZ000-WYZ000-272015-

Mesoscale Discussion 1424
NWS Storm Prediction Center Norman OK
0108 PM CDT Thu Jul 27 2017

Areas affected...extreme southeast Montana through northeastern
Wyoming

Concerning...Severe potential...Watch possible

Valid 271808Z - 272015Z

Probability of Watch Issuance...40 percent

SUMMARY...A few strong to severe storms are possible from southeast
MT into northeast WY this afternoon. Isolated large hail and locally
strong to damaging wind gusts will be the primary threats through
early evening. Trends will continue to be monitored for a possible
WW.

DISCUSSION...Visible satellite imagery shows a corridor of enhanced
cumulus along a surface trough from southeast MT through northeast
WY. Modified continental-polar air with low 60s F dewpoints has
advected into this region beneath modest (6.5-7C/km) mid-level lapse
rates, resulting in moderate instability with 1000-1500 J/kg MLCAPE.
Strong diabatic warming and forcing for ascent associated with an
MCV located over southeast MT will foster thunderstorm initiation
this afternoon. A slight enhancement of the flow aloft might occur
south of the vorticity maximum over southeast MT with effective bulk
shear from 30-40 kt. This environment will promote both multicell
and some supercell structures as storms intensify during the
afternoon.

..Dial/Grams.. 07/27/2017

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

ATTN...WFO...UNR...CYS...BYZ...

LAT...LON   45440493 44930453 44100419 43150421 42690451 43000506
            43810533 44960531 45440493




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