954
FXUS63 KUNR 190906
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
206 AM MST Sun Jan 19 2025

.KEY MESSAGES...

-Bitterly cold temperatures and wind chills into Tuesday morning
-Coldest wind chills late tonight/Monday morning
-Flurries possible northeastern Wyoming today


&&

.DISCUSSION...(Today Through Saturday)
Issued at 132 AM MST Sun Jan 19 2025

08Z analysis shows a Hudson Bay upper low swinging a broad/deep
trough through the Midwest early this morning. Cyclonic northerly
flow aloft continues over the forecast area. At the surface, an
elongated area of cold high pressure extends southward out of
Alberta/Saskatchewan east of the Rockies all of the way south into
Texas.

High temperatures today will mainly be in the single digits above
zero with breezy to windy northwest winds producing bitterly cold
wind chill readings. There is a slight chance for light snow
showers or flurries, mainly over northeastern Wyoming.

Another blast of arctic air will push into the region late
tonight/early Monday with winds increasing behind yet another
cold front. This will lead to the coldest wind chill readings of
this outbreak and an upgrade to an extreme cold warning may be
needed, especially over northwestern South Dakota where wind
chills colder than 40 below zero are possible. Northwest winds
gusting to around 40 mph are possible on the western South Dakota
plains on Monday, with high temperatures remaining below zero for
much of the area.

The winds will decrease on Monday evening and become southwesterly
overnight, as the arctic high shifts off to the south and a
surface trough forms over the western Dakotas. This trough will
mark the boundary between the coldest air to the east and the
warmer/downslope air to the west. Tuesday high temperatures will
vary greatly, being highly dependent on the location of the N-S
oriented surface trough.

The next shortwave/clipper type system will bring low chances for
light snow Tuesday night through Wednesday night along with
breezy to windy northwest winds.

Confidence in temps and weather drop off sharply toward the end
of next week due to high variability in model solutions. Negative
AO tendencies beyond next week tend to favor another possible
arctic outbreak toward the end of the month.

&&

.AVIATION...(For the 06Z TAFS Through 06Z Sunday Night)
Issued At 1017 PM MST Sat Jan 18 2025

VFR conditions are generally expected through the forecast period.
Some light snow showers/transient MVFR conditions are possible
across portions of NE WY after 15-17z as another quick moving
system drops through the region.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...Cold Weather Advisory until 11 AM MST /noon CST/ Tuesday for
     SDZ001-002-012>014-024>032-041>044-046-047-049-072>078.
WY...Cold Weather Advisory until 11 AM MST Tuesday for WYZ054>060.
&&

$$

DISCUSSION/KEY MESSAGES...10
AVIATION...SE