SPC MD 1166


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Mesoscale Discussion 1166
NWS Storm Prediction Center Norman OK
0210 PM CDT Thu Jul 26 2018

Areas affected...Portions of south-central MT

Concerning...Severe potential...Watch unlikely 

Valid 261910Z - 262145Z

Probability of Watch Issuance...20 percent

SUMMARY...Thunderstorms capable of severe hail and severe wind gusts
will evolve through the area this afternoon but are expected to be
isolated enough to preclude a Watch.

DISCUSSION...A subtle perturbation in relatively moist mid-to-upper
level flow rounding the top of the western ridge, sufficient
mid-level lapse rates, and surface heating within low 50s dewpoints
has contributed to isolated thunderstorms early this afternoon. 
Continued heating should contribute to further destabilization ahead
of the storms moving off the Big Snowy Mountains, as well over the
higher elevations to the west and northwest of there.  

An additional storm or two is expected to emerge from the decaying
storms currently over Musselshell county as a corridor of increasing
MLCAPE and steepening low-level lapse rates becomes established over
the area.  Effective shear in the 35-45 kt range should allow for
supercell structures and severe hail/wind potential as these storms
respond to the increasing CAPE.  Additional thunderstorms should
develop off the Little and Big Belt Mountains to the north and west
into the Glacier National Park area, where a similar environment
will also support a severe hail/wind threat.  However, given the
weak large-scale forcing for ascent and somewhat limited
instability, the coverage of storms/severe weather is expected to
remain low enough to preclude a Watch, but the area will be
monitored throughout the afternoon for signs of a more widespread
severe threat.

..Coniglio/Hart.. 07/26/2018

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


LAT...LON   45130893 45241010 45841194 46961336 47621375 48251393
            48791351 48771306 48201179 47500999 47040881 46460782
            45870748 45480754 45010773 45120883 45130893 

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