ZCZC SPCSWOMCD ALL
ACUS11 KWNS 102304 
SPC MCD 102304 
NDZ000-MTZ000-110300-

Mesoscale Discussion 1874
NWS Storm Prediction Center Norman OK
0504 PM CST Sat Dec 10 2016

Areas affected...Portions of northeast MT and western ND

Concerning...Heavy snow 

Valid 102304Z - 110300Z

SUMMARY...A band of moderate to locally heavy snow will spread
eastward into the evening hours, capable of producing local snowfall
rates to 1 inch per hour.

DISCUSSION...Modest ascent associated with warm advection and
frontogenetic processes -- accompanying a relatively fast-moving
midlevel trough -- will continue to foster the eastward spread of a
band of snow. While liquid-equivalent precipitation will be limited
in magnitude given the relatively low PW in place, deep dendritic
growth zones associated with the very cold air mass will support
large snow:liquid ratios (20:1 to 30:1). As a result, snowfall rates
locally reaching 1 inch per hour may accompany this band of snow,
which could persist as long as a few hours in any given location.
Steeper midlevel lapse rates on the upshear side of the snow band
may also provide a slight convective enhancement to snowfall rates,
and related shallow turret structures have been noted with cloud
fields west of the Glasgow, MT area per visible imagery. However, a
longer-duration snowfall event is not likely given the progressive
nature of the open wave. Heavy snow has already been reported at the
ASOS in Glasgow, MT. Heavier snow should enter western ND by around
00-02Z, and then spread east of the discussion area by late evening.

..Cohen/Picca.. 12/10/2016

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

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

LAT...LON   47270483 47890687 48520620 48360156 47580109 47210247
            47270483 

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