Area Forecast Discussion
Issued by NWS Rapid City, SD

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000
FXUS63 KUNR 111930
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1230 PM MST Thu Jan 11 2018

.UPDATE...
Issued at 1053 AM MST Thu Jan 11 2018

Wind chills across northwest South Dakota still around -25F.
There will be a slight improvement this afternoon, with wind
chills dropping again tonight. Have extended the Wind Chill
Advisory through Friday morning.

&&

.DISCUSSION...(Today Through Wednesday)
Issued at 209 AM MST Thu Jan 11 2018

Latest upper analysis shows a trough over central North America
with the trough axis currently moving eastward and away from the
forecast area. At the surface, cold high pressure is moving into
the region from the northwest. A tight sfc pressure gradient is
producing gusty northwest winds over the South Dakota side of the
forecast area, which combined with the cold air, is producing very
cold windchill readings this morning. A Wind Chill Advisory has
been issued for far northeastern Wyoming, northwestern South
Dakota and the plains east of the Black Hills, until 1100 AM MDT
this morning. The winds will diminish some this afternoon but cold
temperatures will remain, with the afternoon highs ranging from
the lower 20s over parts of northeastern Wyoming and the Black
Hills, the the single digits above zero over northwestern South
Dakota.

The next shortwave system and a cold front will affect the area
tonight into Friday. Light snow or flurries will fall over much of
the area, however accumulations will be minimal, with less than an
inch at most locations. Cold weather will persist through Friday,
with a gradual warm up from Saturday into Sunday, ahead of the
next cold front. An upper shortwave trough on the west side of the
Hudson Bay low will swing southward across the northern plains
Sunday night bringing colder air back into the region and some
light snow or flurries. The colder air may be relatively short-lived
early next week before temperatures rise back to near average
levels by midweek.

&&

.AVIATION...(For the 18Z TAFS Through 18Z Friday)
Issued At 1229 PM MST Thu Jan 11 2018

VFR conditions are expected through this evening. MVFR conditions
will return after midnight across much of the area, as some light
snow moves through. The MVFR conditions with light snow will
persist through Friday morning.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...Wind Chill Advisory until 11 AM MST Friday for SDZ001-002-
     012>014-032-073.

WY...None.
&&

$$

Update...7
DISCUSSION...10
AVIATION...15



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