SPC MD 1473

MD 1473 CONCERNING SEVERE POTENTIAL...WATCH POSSIBLE FOR EASTERN MONTANA/WESTERN NORTH DAKOTA

Mesoscale Discussion 1473
NWS Storm Prediction Center Norman OK
0616 PM CDT Wed Aug 12 2020

Areas affected...eastern Montana/western North Dakota

Concerning...Severe potential...Watch possible 

Valid 122316Z - 130115Z

Probability of Watch Issuance...40 percent

SUMMARY...Isolated storm development is expected to continue over
the eastern Montana vicinity, though more widespread convection
should remain north of the international border.  Locally damaging
winds will accompany any stronger storm, though need for a WW
remains questionable due to the rather isolated nature of the risk
that is expected this evening.

DISCUSSION...Latest visible satellite and radar loops show storms
developing convection across east-central and northeast Montana at
this time, with more widespread convection north of the U.S./Canada
border into southern Saskatchewan.  The storms are initiating in
response to increasing ascent/uvv -- per WV imagery -- as a
short-wave trough centered over western Montana continues shifting
east-northeastward.

Greater instability is indicated over southern Saskatchewan --
coincident with more robust/widespread storm development.  Farther
south, some capping issues are noted in model data -- particularly
eastward into North Dakota -- likely limiting storm coverage at this
time.  Additionally, shear remains rather modest across the area,
with only around 20 kt westerly flow at mid levels.  While flow
aloft -- both low-level and deep-layer -- will increase somewhat
this evening, capping will also reassert itself as the boundary
layer cools.  These factors continue to cast uncertainty with
respect to degree of severe risk, and any corresponding need for
potential WW issuance.  While locally damaging winds can be expected
with any stronger storm, given the deep/dry mixed layer, we will
continue to evaluate the environmental evolution and related trends
in convective development, to further assess the need for watch
issuance.

..Goss/Guyer.. 08/12/2020

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

ATTN...WFO...BIS...BYZ...GGW...

LAT...LON   48790485 49000407 48970039 47060085 46600216 46560420
            47130475 48790485 

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