Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 110945

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
245 AM MST Mon Dec 11 2017

.DISCUSSION...(Today Through Sunday)
Issued at 241 AM MST Mon Dec 11 2017

Water vapor imagery depicts a strong circulation associated with
the upper wave moving through the Dakotas. A 120 kt jet is diving
south with the wave, over MT, northeastern WY, and western SD.
Mid/high clouds are streaming into the area with the jet, and an
area of lower ceilings is also pushing into SD from western ND.
Northwesterly winds are gusty across the western SD plains,
especially just east of the Black Hills, where sustained winds are
already 30-40 mph. Temperatures at 2 AM range from the 30s across
less windy northeastern WY, to the 40s and 50s across the western
SD plains.

Forecast soundings for HRRR, RAP, NAM, and GFS continue to show very
strong winds mixing down early this morning, especially east of the
Black Hills. NAM is still showing a 5-6 mb pressure difference
across the Hills through 15Z this morning. Sustained winds of 40+
mph with gusts of 60+ mph are expected for the plains east of the
Hills, so have issued a High Wind Warning. Have also expanded the
Wind Advisory to include the southeastern foothills and much of
southern SD. Winds across northwestern SD may reach warning criteria
at times, but for the most part expecting a high-end Wind Advisory
event. The strongest winds for northwestern SD and areas just east
of the Black Hills will be this morning, and gradually diminish
through the afternoon. Areas farther south will be gustiest during
the middle of the day. Wind-Advisory-criteria winds will be possible
across some locations until 00Z, so all headlines end then.

South central SD may see some light rain/snow today with the passing
wave, but most of the precip will stay to the east. Highs today will
be generally in the 40s.

Warm air will move into the area Tuesday, ahead of the next wave.
Highs will warm back into the 50s. The ECMWF and GFS are in better
agreement about the track and timing of the Tuesday night/Wednesday
wave, although the ECMWF is a bit stronger. NAM is showing another
tight pressure gradient over the Black Hills early Wednesday, so
more downsloping wind will be possible. Gusty northwest winds are
expected across the SD plains on Wednesday as well, and highs will
be in the 40s. A reinforcing shot of colder air and continued breezy
winds are expected for Thursday with another passing shortwave.
Upper ridging and a warm front will bring another mild day Friday,
but chances for precipitation increase for the weekend as a stronger
wave pushes through.


.AVIATION...(For the 06Z TAFS Through 06Z Monday Night)
Issued At 1016 PM MST Sun Dec 10 2017

VFR conditions will continue through Monday afternoon. Northwesterly
winds will become strong overnight as a cold front crosses the
region. Gusts over 45kts are possible over the plains of northwestern
South Dakota. Winds will diminish late Monday afternoon.


SD...Wind Advisory until 5 PM MST /6 PM CST/ this afternoon for

     High Wind Warning until 5 PM MST this afternoon for SDZ026-031-



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