SPC MD 1008


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Mesoscale Discussion 1008
NWS Storm Prediction Center Norman OK
0254 PM CDT Thu Jun 06 2019

Areas affected...Portions of southwestern and central Montana

Concerning...Severe potential...Watch possible 

Valid 061954Z - 062200Z

Probability of Watch Issuance...40 percent

SUMMARY...Storm initiation is likely in the next hour or two.
Scattered severe thunderstorms will be possible with an attendant
risk of large hail and damaging wind gusts. Storms may grow upscale
into an MCS and pose more of damaging wind gusts threat later this
afternoon. A WW is possible in the next two hours.

DISCUSSION...Visible satellite shows increasing cumulus development
across the Bitterroot and vicinity with a couple upstream mid-level
waves approaching southwestern Montana on water vapor imagery. While
moisture will be limited (dewpoints in the mid 40s to perhaps near
50 F), strong surface heating has pushed temperatures into the mid
to upper 80s F across portions of southwestern and central Montana.
A modestly buoyant (MLCAPE of 500-1000 J/kg, greater values with
eastward extent) airmass and steep mid-level lapse rates of 7.5-8.5
C/km will support storms capable large hail. Storms should initially
be discrete with 40-55 kts of effective deep-layer shear. Inverted V
low-level thermodynamic profiles will also support the threat for
damaging wind gusts. Given how efficient outflow production will
likely be as well as a tendency to have several splitting storms
interact (long, generally straight hodographs), upscale growth into
an MCS later this afternoon will be possible. Should an MCS develop,
strong deep-layer flow parallel to storm motion would support a
wider threat of damaging wind gusts. A WW may be needed in the next
two hours.

..Wendt/Hart.. 06/06/2019

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


LAT...LON   45641403 47601159 48820976 48810851 48090782 46700866
            45441009 44961148 44611315 44801382 45231419 45641403 

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