Area Forecast Discussion
Issued by NWS Rapid City, SD

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000
FXUS63 KUNR 041728
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1028 AM MST Sun Dec 4 2016

.SHORT TERM...(Today Through Monday Night)
Issued at 306 AM MST Sun Dec 4 2016

Upper low continues to spin over the Gulf of California, with
northern trough moving through the central CONUS. Skies are partly
cloudy across the area, with a patch of mid level clouds over
northeast WY. Radar indicates a few light echoes associated with
the mid clouds with Gillette reporting a light snow shower in the
past 2 hours. Temperatures at 3am are in the 20s and lower 30s.

Today...Mild weather will continue today as a weak upper trough
passes over the northern plains. Surface winds will become
southwesterly ahead of an approaching trough, and temperatures
will warm into the mid 30s and 40s.

Tonight...The next upper trough will begin moving into the region
late, bringing snow after midnight across far northwestern SD,
northeastern WY, and the Black Hills. Arctic air and gusty
northwesterly winds will follow a strong cold front that will
enter northeast WY after midnight. Snow and blowing snow will be
on the increase after the frontal passage, with visibilities being
reduced to less than half a mile at times. Temperatures in the 30s
will quickly fall into the 20s as the front moves through. A
winter weather advisory will be in effect for much of northeast
WY after midnight.

Across the remainder of western and central SD...mild temperatures
will continue through the night time hours just ahead of the
arctic front. Low temperatures will be in the mid 20s to mid 30s.

Monday...Arctic front will be through much of northeast WY and
northwest SD by morning...and will cross the remainder of the
forecast area during the day. The best chances of accumulating
snow will remain across northeast WY and the Black Hills, but most
locations will see at least a light dusting of snow as the arctic
front moves through. Gusty northwest winds of 20 to 25 mph will
continue across northeast WY...with winds increasing to 20 to 30
mph across the SD plains by mid morning. The winter weather
advisory for snow and blowing snow will continue across northeast
WY through late afternoon. Morning temperatures in the 20s across
northeast WY and northwest SD will continue to slide during the
day, falling into the teens by the afternoon. Wind chills will
fall to near zero by late afternoon.

Further south and west across SD, temperatures will start falling
by mid morning with the exception of far south central SD. High
temperatures will climb into the mid to upper 30s by noon before
the cold front finally moves through. Wind chill readings across
the SD plains east and south of the Black Hills will fall into
the teens by late afternoon.

Monday night...Broad upper trough will continue to sink south
across the area overnight...with surface arctic high pressure
settling across the northern High Plains. Light snow will
diminish early with skies remaining variably cloudy. Temperatures
will continue to fall through the night, with lows ranging from 5
to 15 degrees. Wind chill readings will fall to below zero across
much of the area.

.LONG TERM...(Tuesday Through Saturday)
Issued at 306 AM MST Sun Dec 4 2016

Significant upper trough hangs out over the northern Plains
Tuesday through Thursday as 1048mb arctic high slowly settles into
the area. As arctic high settles in, modest gradient expected
Tuesday and Wednesday on the western SD Plains which will result
in breezy / windy areas and bitterly cold wind chills. Suspect
wind chill advisory will be needed for western SD later Tuesday
into Thursday. Temperatures will be 20-30F below normal.

Surface high shifts east Friday into next weekend as upper level
trough moves east. Warmer air will invade southwest portions of CWA,
but low level easterly component to wind over western SD may keep
the arctic air longer east of the Black Hills. Easterly component to
wind will be created by low pressure moving along edge of arctic air
across WY into NE Friday night and Saturday. Strip of -SN expected
across CWA and pops reflect this thinking.

&&

.AVIATION...(For the 18Z TAFS Through 18Z Monday)
Issued At 1024 AM MST Sun Dec 4 2016

VFR conditions are expected through this evening. An arctic cold
front, followed by gusty northwest winds, will move into
northeastern Wyoming and western South Dakota late tonight/early
Monday morning. Areas of MVFR/IFR conditions will develop with low
stratus, -SN and possibly areas of blowing snow.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...None.
WY...Winter Weather Advisory from midnight tonight to 5 PM MST Monday
     for WYZ054>058.

&&

$$

SHORT TERM...15
LONG TERM...Helgeson
AVIATION...10



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