Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 271122
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
422 AM MST Fri Jan 27 2023

.DISCUSSION...(Today Through Thursday)
Issued at 310 AM MST Fri Jan 27 2023

Current surface analysis shows low pressure along the
MN/Canadian border, with warm front well east of the forecast area
and arctic front from central ND to northeast MT. Upper level
analysis shows broad trough covering the central and eastern US,
with ridge remaining off the west coast. Active and fast
northwesterly flow continues from southwest Canada into the northern
Rockies and Great Plains. A tight pressure gradient over the Dakotas
is resulting in gusty west to northwest winds to over 50 mph across
much of the plains. Winds are starting to gradually decrease across
far western SD and will continue to decrease through the early
morning hours from west to east. Light snow is tapering off over the
Black Hills, with isolated rain and snow showers over the southwest
SD plains as the current disturbance starts to slide southeast of
the area. Temps are mild early this morning, mostly in the 30s.

Active weather will continue into the weekend, with much colder air
arriving late today and tonight as the arctic front to the north
slides through the area. The next shortwave disturbance to pass
through our area is located over southern British Columbia and
Alberta and will race quickly southeast across MT today. As this
disturbance interacts with the southward moving front across our
area late today and tonight, a band of light to moderate snow will
develop from southeast MT/northeast WY to the Black Hills and
southern SD. The models are in general agreement on where and when,
but still off a bit on the exact location and timing across the
area. EC and Canadian ensembles are a bit farther north, with the
NAM even farther north, compared to the GFS ensemble, but all have
drifted farther north in the last couple of runs. There could be a
bit of upslope enhancement during the evening across the
northeastern and eastern slopes of the Black Hills as northeasterly
winds develop. A heavier band of snow will then set up near the
south central SD/north central NE border and slide east later this
evening and overnight. Winds will not be too gusty as colder air
moves in, but some blowing and drifting of snow is possible toward
south central SD tonight into Saturday morning. With probabilities
of 3 inches or more of snow relatively high late today into Saturday
morning from northeast WY to the Black Hills and much of
southwest/south central SD, winter wx advisories have been expanded
across these areas and a warning has been issued for Tripp County
where 6+ inches is likely tonight into early Saturday. There could
still be some additional adjustments to headlines today, depending
on any changes with placement of snowfall.

As the front slides south of the area by Saturday morning, arctic
air will filter in, with well below average temperatures continuing
into early next week. The coldest air will be in place Sunday and
Monday, when highs will only be in the single digits and lower
teens, with lows below zero and wind chills as low as 20 below to
around 30 below. Weak disturbances aloft will bring continued
chances for light snow Saturday into Sunday, especially from
northeast WY into southwest SD, with additional light accumulations
likely through that period.

Medium range models have been consistent for the last day or two
with warmer air moving into the area toward midweek, with near to
above average temps looking more likely late week. At this point, it
looks mostly dry for next week, with a weak disturbance or two
possibly bringing a few showers with the milder air later in the
week.

&&

.AVIATION...(For the 12Z TAFS Through 12Z Saturday Morning)
Issued At 418 AM MST Fri Jan 27 2023

LCL MVFR conditions in -SHSN are possible this morning. A large
band of snow with widespread IFR conditions will move into
northeastern Wyoming and northwestern South Dakota later this
afternoon and will spread southeastward across the rest of the
area this evening/overnight.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...Winter Weather Advisory from 5 PM this afternoon to 5 PM MST
     Saturday for SDZ012-026-030-031-042-072>074.
     Wind Advisory until 5 AM MST /6 AM CST/ early this morning for
     SDZ014-032-043-046-047-049.
     Winter Weather Advisory from 3 PM this afternoon to 5 PM MST
     Saturday for SDZ024-025.
     Winter Weather Advisory from 5 PM this afternoon to 11 PM MST
     Saturday for SDZ027>029-041.
     Winter Weather Advisory from 5 PM MST /6 PM CST/ this afternoon
     to 11 AM MST /noon CST/ Saturday for SDZ032-043-044-046-047.
     Winter Storm Warning from 6 PM this evening to noon CST Saturday
     for SDZ049.
WY...Winter Weather Advisory from 5 PM this afternoon to 5 PM MST
     Saturday for WYZ071.
     Winter Weather Advisory from 3 PM this afternoon to 5 PM MST
     Saturday for WYZ054-056-057.
     Winter Weather Advisory from 5 PM this afternoon to 11 PM MST
     Saturday for WYZ055-058.
&&

$$

DISCUSSION...26
AVIATION...10


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