Area Forecast Discussion
Issued by NWS Rapid City, SD

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000
FXUS63 KUNR 062346
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
446 PM MST Wed Dec 6 2017

.DISCUSSION...(This Evening Through Wednesday)
Issued at 250 PM MST Wed Dec 6 2017

Current surface analysis shows a Canadian cold front sliding
south of the forecast area now. Upper level analysis shows low
pressure over southern Hudson Bay, with large trough covering a
good portion of the US. A ridge lies along the west coast with
strong northwest flow remaining over the Northern Plains. Upslope
enhanced snowfall continues across the northern Black Hills. Any
snow elsewhere has mostly tapered off to a very light snow or
flurries. Snowfall totals on the plains today have mostly been an
inch or less, with local amounts closer to 2 inches. Snowfall
totals over the northern Hills area have been mostly in the 2 to 6
inch range since last night. Temps are generally in the mid teens
to mid 20s. Gusty winds have tapered off some and will continue
to gradually diminish late today, so have cancelled the wind
advisory. Will keep winter weather advisory for the northern Hills
going through at least the late afternoon, but conditions should
improve greatly there this evening.

After a cold night behind the passing front. A warmup will take
place for late week and into the weekend as the large upper trough
shifts a bit to the east, allowing warmer air under the western
ridge to gradually build in. Cold front will shift back north and
east as a warm front on Thursday, allowing highs to get back to near
average levels in most areas. A weak disturbance aloft will interact
with the eastward moving front Thursday morning to produce a period
of upslope snowfall over the northern Black Hills. Could see another
inch or two over favored areas during the morning. Brisk west to
northwest winds will develop during the day, especially across
northeast WY and northwest SD.

Temps will progressively get warmer each day from Friday through
Sunday, with highs over the weekend mostly in the upper 40s and 50s.
Breezy to windy conditions can be expected at times, especially
later Friday and Sunday. Dry weather is expected Friday through
Sunday. A backdoor front is progged to clip the area Sunday night,
with more seasonable temps returning for Monday. There could be some
showers with the front, but right now it looks like a mainly dry
passage. At this time, it looks like the front will shift back east
of the area Tuesday and Wednesday, with above average temperatures
in the forecast.

&&

.AVIATION...(For the 00Z TAFS Through 00Z Thursday Evening)
Issued At 439 PM MST Wed Dec 6 2017

MVFR-IFR conds as well as some light snow can be expected in a
frontal zone over western SD and NE WY this evening. This front
will begin to push back east with drier air working in from the
west. Conds will trend VFR over NE WY from west to east this
evening, with MVFR-IFR cigs spreading east onto the SD plains.
Conds at KRAP will be dependent on the amount of downsloping and
local drying, but attm will hold MVFR cigs at the terminal
through evening. This may need to be extended into Thur morning.
Otherwise, another weak impulse will advect through the area Thur,
possibly supporting some light snow and areas of MVFR cigs. Conds
should trend VFR all places Thur evening.

&&

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

WY...Winter Weather Advisory until 11 PM MST this evening for WYZ057.

&&

$$

DISCUSSION...26
AVIATION...JC



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