Area Forecast Discussion
Issued by NWS Rapid City, SD

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438
FXUS63 KUNR 012131
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
231 PM MST Thu Dec 1 2016

.SHORT TERM...(This Evening Through Friday Night)
Issued at 231 PM MST Thu Dec 1 2016

Deep and broad upper trough continues across much of the CONUS with
NW flow aloft persisting over the northern plains. Water vapor shows
a series of upper waves from Alberta to Montana and Wyoming. Cloud
cover remains across the much of the CWA with some breaks in the
deck near the eastern Black Hills and portions of northeast Wyoming.
Temperatures are generally in the 30s across much of the area.
Tonight...low clouds now over central South Dakota will develop back
westward across the western SD plains. Areas of fog are also
expected to develop later this evening and remain into the morning
hours Friday. Some areas could see visibility restrictions under a
half mile at times. Forecast soundings show it within the realm of
possibility that some flurries could develop from these clouds...but
thinking areas of fog will be the more likely scenario. Lows tonight
will drop into the teens to low 20s. Fog will dissipate later Friday
morning with some sunshine returning...however wouldn`t be surprised
if fog/low clouds persisted into the afternoon across central SD.
Highs Friday will again reach the 30s across most locations and low
will again drop down into the teens. Some locations may hit the
single digits if radiational cooling is strong enough.

.LONG TERM...(Saturday Through Thursday)
Issued at 231 PM MST Thu Dec 1 2016

Another shortwave trough will cross the forecast area on Saturday
afternoon and evening, creating a slight chance of snow over small
parts of northeastern Wyoming and northwestern South Dakota, and
also over the northern Black Hills. WAA in westerly flow aloft
will bring slightly warmer, though still near average temperatures
on Sunday.

On Monday, a low pressure center crossing North Dakota will swing a
cold front across the forecast area followed by very cold air
flowing southward out of Canada. Expect a chance of light snow as
the cooler air flows in from Monday afternoon through Tuesday.

Latest extended model runs continue to vary greatly with the
location of the various forecast features and possibility of
precip but agree on the much colder than average temperatures on
Tuesday and Wednesday with slightly warmer air pushing in from the
west on Thursday.

&&

.AVIATION...(For the 00Z TAFS Through 00Z Friday Evening)
Issued At 231 PM MST Thu Dec 1 2016

Areas of MVFR/LCL IFR CIGS across parts of northwestern and
central South Dakota will continue into the evening. VFR
conditions will occur over most of northeastern Wyoming into the
evening and local MVFR conditions are expected over the Black
Hills. Widespread IFR conditions will develop over western and
central South Dakota this evening and over parts of northeastern
Wyoming toward Friday morning. The IFR conditions will continue
through Friday morning.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...None.
WY...None.
&&

$$

SHORT TERM...13
LONG TERM...10
AVIATION...10



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