SPC MD 1745



MD 1745 CONCERNING HEAVY SNOW FOR SOUTHEAST MONTANA…PORTIONS OF NORTHERN WYOMING…EXTREME WESTERN SOUTH DAKOTA

MD 1745 Image


Mesoscale Discussion 1745
NWS Storm Prediction Center Norman OK
0948 PM CST Sun Dec 30 2018

Areas affected...Southeast Montana...portions of northern
Wyoming...extreme western South Dakota

Concerning...Heavy snow 

Valid 310348Z - 310845Z

SUMMARY...Heavy snowfall (up to 1 in/hr rates in the lower terrain
and 2 in/hr rates in the higher elevations) is expected for at least
the next few hours. With strong sustained northwesterly winds
accompanying the cold front, a few brief instances of blizzard
conditions cannot be ruled out.

DISCUSSION...A relatively strong, deep cold front (extending up to
700 mb) is rapidly progressing across portions of the northern
Rockies, providing strong low-level convergence and deep-layer CAA
(through at least 850 mb) across complex terrain. Frontal
convergence, combined with orographic lift, will help to induce
vigorous rising motion through a near-saturated 700 mb layer, and a
very deep (1000-1500 m) dendritic-growth zone, promoting very
efficient dendrite production and associated snowfall accumulations.
Up to 1 in/hr snowfall rates are likely in the lower terrain, but
higher rates (2 in/hr) may be common in the higher terrain, where
upslope flow and subsequent orographic lift may enhance snowfall
production.

In addition, strong northwesterly surface winds are accompanying the
cold front, with up to 30 knot sustained winds (with higher gusts)
recently observed by the Johnson City/Buffalo WY ASOS. As such, a
few instances of blizzard conditions may be observed over the next
few hours as the cold front passes.

..Squitieri.. 12/31/2018

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

ATTN...WFO...UNR...CYS...BYZ...RIW...

LAT...LON   43630715 44560855 45240917 45740906 45980870 46050784
            45910624 45710526 45470422 45250360 44720326 44100324
            43560386 43390488 43400580 43630715 

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