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ACUS11 KWNS 231232
SPC MCD 231231

Mesoscale Discussion 0199
NWS Storm Prediction Center Norman OK
0631 AM CST Thu Feb 23 2017

Areas affected...Portions of western and northern Nebraska...and
extreme south-central South Dakota

Concerning...Heavy snow

Valid 231231Z - 231700Z

SUMMARY...Heavy snowfall rates around 1 inch/hour are expected
through the morning from part of north-central NE (in vicinity of
Keya Paha County through Cherry and Sheridan Counties, and perhaps
into western parts of the NE Panhandle).  This snowfall rates should
also develop into extreme south-central SD (primarily from Bennett
to Tripp Counties).

DISCUSSION...Trends in mosaic radar imagery indicated mesoscale
banding developed around 09Z, and has persisted through 12Z so far
across mainly northern Cherry County to Sheridan County.  Surface
observations show this precipitation is in the form of snow, with
this region located north of the wet-bulb 0C line which at 12Z
extended from northeast to southwest NE.  Northeasterly surface
winds are expected to increase some this morning into the afternoon,
as an area of low pressure forms across eastern CO and deepens,
tracking into west/southwest KS this afternoon.  This indicates
cooler temperatures should be maintained across the discussion area
today to sustain the precipitation type as snow.

Trends in mosaic radar imagery indicated some increase in intensity
within the snow bands.  This trend should persist through this
morning, as height falls/DPVA spread into western and central NE,
with the approach of the Great Basin trough, further enhancing
midlevel frontogenesis within the 600-700-mb layer.  In addition,
11Z RAP forecast soundings indicated the upward vertical motion in
the 600-700-mb layer will occur within the favorable dendritic
growth zone this morning, supporting the heavier snowfall rates.

..Peters.. 02/23/2017

...Please see for graphic product...


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