Area Forecast Discussion
Issued by NWS Rapid City, SD

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000
FXUS63 KUNR 051714
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1014 AM MST Tue Dec 5 2017

.DISCUSSION...(This Afternoon Through Monday)
Issued at 636 AM MST Tue Dec 5 2017

Upper level analysis has a large trof across the north central
CONUS with large ridge off the West Coast. in between, very fast
northerly flow is present across the Northern Plains. Skies are
cloudy with a band of light snow present across the South Dakota
plains. At the surface, low pressure is located over the Great
Lakes region and high pressure remains across the Rockies.
Temperatures at 3am are mainly in the teens and 20s, with west to
northwest winds at 10 to 25 mph.

Strong northerly flow will continue over the area today, and with
decent low level mixing and weak shortwave moving through, very
strong winds will develop late this morning across the South
Dakota plains and persist through late this afternoon. A High
Wind warning will be in effect from northwest SD through west
central SD with 30 to 45 mph winds expected, with gusts to 65 mph
possible. Additionally, a weak shortwave will move through the
area, bringing some light snow to northwest SD and the northern
Black Hills. While accumulations will be minimal across northwest
SD, an inch or two of upslope enhanced snow is expected across the
northern Black Hills.

Strong northerly flow will persist through the week as the main
upper trof sets up across the eastern CONUS, and a ridge builds
over the west. North to northwest winds will stay windy during the
daytime hours for the next several days, and there will be daily
chances for light snow -- especially over the northern Black Hills
as weak shortwave energy crosses the area in the strong north
flow. The cold airmass will stick around through midweek, with
below average highs in the 30s. Towards the end of the week, a
gradual warming and drying trend is expected as the western upper
ridge shifts eastward into the Great Basin area.

&&

.AVIATION...(For the 18Z TAFS Through 18Z Wednesday)
Issued At 1007 AM MST Tue Dec 5 2017

Another fast moving weak weather system will move through the
area today. This will bring some light snow to the northern Black
Hills, parts of NE WY, and NW SD for much of the day, with MVFR
and local IFR conditions. Very strong NW winds will redevelop
this afternoon, especially on the SD plains, with wind gusts to 65
mph possible. This may support patchy blowing snow with reduced
visibilities across mainly NW SD. Conditions may improve briefly
this evening as snow decreases, but then ceilings and visibilities
will diminish again towards morning as snow redevelops across the
same areas.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...Wind Advisory until 6 PM MST /7 PM CST/ this evening for SDZ027-
     030-041>044-046-074.

     High Wind Warning until 6 PM MST this evening for SDZ001-002-
     012>014-025-026-031-032-072-073.

WY...High Wind Warning until 6 PM MST this evening for WYZ071.

&&

$$

DISCUSSION...15
AVIATION...Pojorlie



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