Area Forecast Discussion
Issued by NWS Rapid City, SD

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000
FXUS63 KUNR 051751
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1051 AM MST Mon Dec 5 2016

.UPDATE...
Issued at 1050 AM MST Mon Dec 5 2016

Current surface analysis shows arctic cold front now clearing
south central SD, with gusty northwest winds and dropping
temperatures behind it. Upper level analysis shows low over south
central Canada, with broad trof sweeping across the Northern
Rockies and northern high plains right now. Areas of snow continue
to cover much of northeast WY and western SD now, with the heavier
areas of snow now mostly to the east and southeast of the Black
Hills in area of convergence. Snow is moving rather quickly to the
east, but areas of snow will continue through the midday hours
before dissipating in the afternoon. Snowfall amounts of 2 to 4
inches have been reported across much of northeast Wyoming as well
as portions of the northern Black Hills area, with mostly an inch
or less elsewhere. Wind gusts to around 50 mph across northwest
and west central SD is producing some areas of blowing snow and
reduced visibilities at times where snow has fallen.

Forecast has been updated to raise pops east of the Black Hills
through the early afternoon. Additional snowfall will generally be
greatest over parts of far southwest SD into the Pine Ridge,
around an inch, with up to an inch elsewhere mainly to to the east
of the Black Hills. Conditions will gradually improve over
northeast WY and the Black Hills this afternoon. Temps will
continue to drop this afternoon, with teens and 20s by around
sunset. Winds will gradually taper off after sunset, but remain
breezy overnight.

&&

.SHORT TERM...(Today Through Tuesday Night)
Issued at 343 AM MST Mon Dec 5 2016

Upper level analysis shows broad troughing over much of the
northern CONUS, with closed lows over Mexico and Saskatchewan.
Clouds and snow are pushing into the northern plains with the
next wave associated with the Canadian low. At the surface, low
pressure and the cold front are moving into far western SD.
Temperatures are in the 20s and 30s across much of the area.

Today...Upper trough will move across the Dakotas today. Snow
has begun across northeastern WY and the Black Hills this
morning, and will expand into the western SD plains as the cold
front moves through. Snow amounts of 2 to 4 inches are expected
across northeastern WY and the northern Hills, with a half inch
or so across the northwestern SD plains.

Another factor with this system will be gusty northwest winds, which
will be aided by cold air advection and pressure rises around 5
mb/3hr. ECMWF and GFS have 850 mb winds around 40 kts over the
western SD plains, but only 15-20 kts over northeastern WY. Expect
some areas of blowing snow over northeastern WY,  with some patchy
blowing snow over the windier but less snowy western SD plains.
A Wind Advisory is in effect for northwestern SD through this
evening. Some brief reductions in visibility will be possible
across western and northwestern SD with any snow showers that move
through.

Today will begin a very cold week as arctic air begins sinking
into the region. Most areas will see falling temperatures by mid
morning to early afternoon. Temperatures will range from the low
20s across northeastern WY and northwestern SD, to the 30s
across south central SD. Some places in the Hills may remain in
the teens. Wind chill readings will approach zero by late this
afternoon. Lows tonight will be mainly in the single digits with
wind chills from zero to 10 below zero.

Tuesday...Upper level trof will shift east as cold surface high
pressure settles into the forecast area. Skies will be variably
cloudy. High temperatures will only be in the teens to low 20s
with bitter wind chills remaining across much of the area. By
Tuesday night, temperatures will range from 5 above to 5 below
zero, with wind chill readings from 10 to 25 degrees below zero.

.LONG TERM...(Wednesday Through Sunday)
Issued at 343 AM MST Mon Dec 5 2016

Deep trof covering the cntrl conus will keep temps very cold
across the nrn plains through Thursday. Zonal flow then sets up
for the end of the week into the weekend, allowing slightly warmer
air to work back into the region beginning Friday. Dry conditions
are expected through Friday, then as the flow becomes a bit more
disturbed over the weekend expect a few chances for light snow to
return.

&&

.AVIATION...(For the 18Z TAFS Through 18Z Tuesday)
Issued At 1014 AM MST Mon Dec 5 2016

Cold front will cont to move across the area today bringing gusty
northwest winds, in excess of 40 knots on the SD plains. Area of
snow along and behind the front will result in IFR/LIFR
visibility across northeast Wyoming and the Black Hills, with
MVFR/IFR visibility across the plains of western South Dakota.
Snow will decreases across the area early this afternoon with
improving conds west to east through afternoon. However areas of
MVFR/IFR ceilings will persist into the afternoon and evening with
sct snsh.


&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...Wind Advisory until 9 PM MST this evening for SDZ001-002-012>014-
     025-026-031-032-072-073.

WY...Winter Weather Advisory until 5 PM MST this afternoon for
     WYZ054>058.

&&

$$

Update...26
SHORT TERM...15
LONG TERM...Johnson
AVIATION...JC


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