667
FXUS63 KUNR 031122
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
422 AM MST Sat Jan 3 2026

.KEY MESSAGES...

-Frontal boundary will sag back south into the region after a
 brief push of warm air this morning

-Some fog expected across NW SD today

-Mild to start next week, with windy conds across the southwest
 Sunday

&&

.DISCUSSION...(Today Through Friday)
Issued at 1234 AM MST Sat Jan 3 2026

Western CONUS ridge will shift east in the period, supporting
mild and dry weather to start next week. However, one more day of
cool temps can be expected on the SD Plains today before warming
finally spreads east. Weak impulse topping the ridge is supporting
WAA aloft this morning, with warmer air mixing down into the
eastern BH foothills. Another day of mild weather in the west,
with cool, cloudy, and foggy weather in the east, esp NW SD.
Frontal boundary will shift back south later this morning, with NE
upslope flow supporting another round of fog and low clouds
across NW SD today. Current hires guidance stops the southern push
of fog/low clouds just north of I90, however, it could certainly
end up farther south, possibly impacting Rapid City. Most places
on the SD Plains will see highs this morning before the front
moves back through, esp in the eastern BH foothills. Further west
across northeast WY and the BH, expect a mild day with highs in
the 50s. Main surge of WAA will ensue tonight as stronger WSW flow
spreads east. Dry downslope flow will spread east with many
locations in the west remaining quite mild over night. However, it
will become breezy to windy, esp across southern Campbell and
Weston Counties where gusts over 45 mph are expected. In addition,
downslope winds are likely along the eastern foothills Sunday
morning, with winds potentially gusting over 45 mph in some areas.
A wind adv may be needed if this signal continues. Much warmer
all places Sunday with highs in the 50s and 60s, warmest in the
lee of the BH where a few mid 60s are possible. Breezy west winds
will also be present, esp across the southern half. Mild and dry
conds will persist through mid next week, until the ridge
flattens some per northern stream troughing. A deeper trough will
move into the west toward the end of the week, with cooler conds
expected and some chances for snow.

&&

.AVIATION...(For the 12Z TAFS Through 12Z Sunday Morning)
Issued At 418 AM MST Sat Jan 3 2026

MVFR/IFR conditions from low clouds and fog will develop across
northwestern SD this morning as a backdoor cold front sags into
the region. The southern extent of these conditions should remain
north of I90, but could clip KRAP for a few hours late this
morning. Winds will turn back southerly with low clouds and fog
pushing back northeast in the afternoon. Fog and low clouds will
linger through tonight over portions of NW SD. Otherwise, VFR
conditions expected through the TAF period over the southwest
half.

&&

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

$$

DISCUSSION/KEY MESSAGES...JC
AVIATION...JC