Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 222332
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
432 PM MST Mon Jan 22 2018

.DISCUSSION...(This Evening Through Monday)
Issued at 1258 PM MST Mon Jan 22 2018

Water vapor shows upper low over northern IA with narrow upper
ridge over the far western Dakotas, and weak upper trof over the
Northern Rockies. At the surface, low center nearly stacked with
upper low...and N/NW winds across much of our cwfa. Wrap around
clouds extend into Tripp county, with mainly clear skies westward.

Weak trof over the Northern Rockies will quickly move into the
Northern Plains tonight, with brief light snow expected from NE WY
into far SW SD and a very small window of upslope in the northern
Black Hills. Moisture very limited so any accumulations will be
minimal. Skies will clear from west to east Tuesday behind
departing trof with highs in the 30s to lower 40s and some breezy
northwest winds.

Progressive upper-level flow is expected to continue through the
extended period, with ridging over the Northern Plains late
Wednesday into Thursday transitioning to troughing by Friday.
Thursday should be unseasonably warm and a bit breezy, particularly
in favored downslope regions east of the Black Hills, as strong west-
to-southwest flow develops ahead of an approaching trough. An
associated cold frontal passage on Friday is expected to be mostly
dry as better upper-level forcing does not materialize until the
system is to our east. However, a quick shot of light snow remains a
possibility late Thursday night into Friday across northeast WY.
Breezy conditions should continue behind the front on Friday, esp.
over the Plains.

Beyond Friday, dry and gradually warming conditions are anticipated
as broad upper-level ridging builds over the central U.S.

&&

.AVIATION...(For the 00Z TAFS Through 00Z Tuesday Evening)
Issued At 430 PM MST Mon Jan 22 2018

VFR conditions expected through the forecast period. Only
exception will be brief MVFR/IFR conditions associated with light
snow showers developing tonight across northeast WY and the Black
Hills tonight and stratus/possible fog in central SD also
tonight. Conds will trend back to VFR all places Tuesday.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...None.
WY...None.
&&

$$

DISCUSSION...Johnson/Sherburn
AVIATION...JC



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