Winner, South Dakota 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

602
FXUS63 KUNR 220459
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
959 PM MST Sat Dec 21 2024

.KEY MESSAGES...

- Mild temperatures (~5-20 degrees above average) and mostly dry
  weather will persist this weekend through Christmas.

&&

.DISCUSSION...(This Evening Through Saturday)
Issued at 1245 PM MST Sat Dec 21 2024

Upper level analysis shows upper ridge axis centered over the
Northern Rockies with dry westerly flow across the forecast area.
Infrared imagery shows stout shortwave trough pushing through
central WA/OR with Pacific moisture streaming into the western third
of the U.S. A surface stationary front is analyzed from eastern MT
through central SD into eastern NE with well above normal
temperatures across the forecast area - highs pushing 60F in NE WY
and far western SD with 30s to 40s as you move east.

The shortwave trough currently in WA/OR will push through the
Northern Rockies and into the Northern Plains Sunday with a weak
surface cool front to follow. Relatively dry mid-levels and boundary
layer will limit precipitation potential, with best chance of
rain/snow north of the forecast area. Given the decent
Q-vector convergence over the area, the LREF grand ensemble
does highlight a narrow band of 25-35% probs of QPF >0.01" across
far northern Harding and Perkins counties through Sunday night
(HREF has <5% probs, with precipitation chances north of the
forecast area). Given the ingredients (or lack thereof), have
decided to keep precipitation out of the forecast with this
package. Expect increased cloud cover and gusty NW winds as the
main sensible weather impacts with this system. Winds will gust to
40 mph across western SD through the afternoon hours, gradually
tapering off with the loss of daytime heating/mixing and the
trough axis shifting east.

Another quick moving shortwave will push through the forecast area
late Monday into early Tuesday morning. Again, moisture will be
lacking with this system: spotty light rain/snow is possible across
NE WY and the Black Hills late Monday, but NBM/LREF indicate a
low probability of measurable precipitation (generally less than
10-15% of QPF >0.05" Monday night). Again, the main weather
impacts will be increased cloud cover and breezy westerly winds.

Dry weather will persist through at least Christmas Day with good
ensemble agreement in above normal temperatures. Expect temperatures
in the upper 30s to into the 50s each day.

&&

.AVIATION...(For the 06Z TAFS Through 06Z Sunday Night)
Issued At 959 PM MST Sat Dec 21 2024

VFR conditions will continue through the period. Gusty northwest
winds will be found across the plains of western South Dakota on
Sunday.

&&

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

$$

DISCUSSION/KEY MESSAGES...SE
AVIATION...7