RSS Mesoscale Discussions from Storm Prediction Center

SPC MD 1676

MD 1676 Image

Mesoscale Discussion 1676
NWS Storm Prediction Center Norman OK
0737 PM CDT Fri Aug 12 2022

Areas affected...West-central MT

Concerning...Severe potential...Watch possible 

Valid 130037Z - 130200Z

Probability of Watch Issuance...40 percent

SUMMARY...Strong to locally severe gusts will be possible this
evening. Watch issuance is possible if observational trends support
a more organized severe wind risk.

DISCUSSION...A loosely organized storm cluster has emerged from the
higher terrain of western MT and is now approaching Great Falls and
vicinity. The KTFX sounding was only weakly unstable (MLCAPE less
than 500 J/kg), but large temperature/dewpoint spreads will support
some threat for strong to severe wind gusts as this cluster moves
eastward this evening, even if individual convective elements within
the cluster are not particularly intense. 

The relatively limited intensity of this cluster renders the need
for a watch uncertain, but if short-term observational trends
support a more organized severe-wind risk through the evening, watch
issuance for parts of central MT will be possible.

..Dean/Goss.. 08/13/2022

...Please see for graphic product...


LAT...LON   47741266 48161206 48371118 48281031 47670988 47220994
            46861001 46781036 46721072 46611110 46551165 46821197
            47131229 47741266 

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SPC MD 1675

MD 1675 Image

Mesoscale Discussion 1675
NWS Storm Prediction Center Norman OK
0652 PM CDT Fri Aug 12 2022

Areas affected...portions of eastern Montana

Concerning...Severe potential...Watch unlikely 

Valid 122352Z - 130115Z

Probability of Watch Issuance...20 percent

SUMMARY...An isolated severe wind/hail threat may persist across
eastern MT over the next few hours with thunderstorm clusters. A WW
issuance appears unlikely given the isolated nature of the more
intense storms.

DISCUSSION...A modest uptick in the severe threat has been noted
across eastern Montana over the past hour, both with a supercell
crossing the U.S. border from Saskatchewan, and with loosely
organized convection near Billings, MT. Despite the presence of a CU
field beneath the anvils of ongoing convection across eastern MT,
buoyancy is scant given the presence of a dry boundary layer
extending to nearly 500 mb (per latest RAP forecast soundings). More
appreciable flow is confined well above 500 mb, contributing to bulk
effective shear values at/below 30 kts. The overall mediocre
CAPE/shear parameter space suggests that storms should remain
isolated and loosely organized over the next couple of hours, with
an isolated severe gust or hailstone possible with the ongoing
storms given steep low and mid-level lapse rates. It is not entirely
out of the question for storms in western MT to grow upscale and
approach eastern MT with a severe gust threat, but the confidence in
this scenario is low. As such, the expected sparse nature of the
severe threat suggests that a WW issuance is not currently

..Squitieri/Goss.. 08/12/2022

...Please see for graphic product...


LAT...LON   48930973 49160938 49250811 49060742 48190579 46560453
            45870432 45430470 45210579 45190692 45250782 45470874
            45790954 46720981 47650979 48930973 

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