Area Forecast Discussion
Issued by NWS Rapid City, SD

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000
FXUS63 KUNR 060536
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1036 PM MST Tue Dec 5 2017

.DISCUSSION...(This Evening Through Tuesday)
Issued at 225 PM MST Tue Dec 5 2017

Broad upper trough is persisting across the eastern half of the
CONUS while upper ridging/Rex blocking pattern has set up over the
western CONUS and Pacific Coast. Deep northwest flow continues
across the Canadian Rockies into the northern Plains with areas of
snow across the CWA. Surface obs show strong northwest winds with
gusts to 50 kts mostly over the northwest to west central SD plains.
Temps are in the 30s to low 40s. Winds will decrease tonight but
remain breezy overnight. Next upper wave near the MT/Canadian border
will swing through late tonight bringing a reinforcing cold front to
the area. Winds behind the front late tonight and Wednesday will be
borderline advisory criteria. Lower atmosphere favorable for upslope
enhanced snow across the usual locations in the northern/Wyoming
Black Hills. Models have generally good agreement on gradually
increasing accumulations through late tonight and Wednesday...with
most areas seeing 2 to 5 inches. Some of the more favorable
locations toward Four Corners, Deerfield, to Cheyenne Crossing could
see higher amounts closer to 5 to 8 inches. Have issued a Winter
Weather Advisory for these areas and through the Wyoming Black Hills
from 06z tonight to 06z Thu. Minor accumulations will be possible
across the plains. Little change to the overall pattern is expected
through the rest of the week into the weekend. A slight eastward
shift of the upper ridge will bring warmer temperatures to the
region with highs reaching into the 50s by the end of the week.

&&

.AVIATION...(For the 06Z TAFS Through 06Z Wednesday Night)
Issued At 1034 PM MST Tue Dec 5 2017

A series of disturbances will move through the region in the next
24 hours, bringing some snow and flight restrictions to parts of
the region. An arctic front will push back to the west and
support snow showers over much of the area late tonight into Wed,
esp the northern Black Hills. Expect flight conds to trend low
MVFR-IFR over much of the area Wed morning, with local LIFR
around the Black Hills and NE WY. It will also be windy across
most of the FA with gusty NW winds, esp in the lee of the Black
Hills.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...Winter Weather Advisory until 11 PM MST Wednesday for SDZ024-028.

WY...Winter Weather Advisory until 11 PM MST Wednesday for WYZ057.

&&

$$

DISCUSSION...13
AVIATION...JC



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