Spearfish, South Dakota 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

110
FXUS63 KUNR 221103
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
403 AM MST Sun Dec 22 2024

.KEY MESSAGES...

- Warm temperatures and mostly dry conditions are expected for
  this weekend through next week.

&&

.DISCUSSION...(Today Through Saturday)
Issued at 212 AM MST Sun Dec 22 2024

Water vapor imagery depicts moisture associated with upper level
wave trekking east across MT/WY. The upper level ridge over the
western US has largely flattened out as the shortwave makes its
way over the Rockies. The Northern Plains sits under zonal,
westerly flow with sfc lee trough stretching from southern AB into
northeastern CO. Mid-level moisture is contributing to increasing
mid to high level cloud cover over the CWA. Temperatures across
northeastern WY into far western SD remain relatively warm (in the
upper 30s to 40s) at this hour thanks to downsloping.

Shortwave trough will and attendant cool front/sfc trof will
traverse the Northern Plains today. The strongest forcing and best
moisture will stay to our north with the majority of the CWA
remaining dry. Most recent HRRR and NAM NEST runs do show a narrow
band of precip associated with the front grazing far northwestern
SD this morning (in the ~15-18z time frame), though chances of
getting anything measurable out of that band are pretty much 0%.
As the front crosses the region, winds will shift to the northwest
and slightly strengthen. Pressure rises aren`t too exciting,
around 1-2 mb/3hr and 850-700mb winds will barely get above 40kt.
So while it will be seasonably breezy this afternoon, any kind of
advisory level winds will be unlikely (HREF grand ensemble paints
0-10% probs of gusts exceeding 45 mph today).

Our next chances for precip will arrive with a shortwave trough
pushing across the region late Monday into early Tuesday. This
system won`t be too strong but the most recent NAM run does depict
weak Q-vector convergence and some moisture over northeastern WY
into western SD. This could be enough to support a few light
rain/snow showers over northeastern WY and the Black Hills.
Chances for anything measurable, however, are pretty low (LREF
grand ensemble paints 0-30% probs for greater than 0.01" QPF and
0-10% probs for greater than 0.05" QPF).

Split flow pattern will continue through the week with the active
southern stream remaining far to our south. With Euro/GEFS/GEPS
ensembles continuing to paint 80-100% probs of 2-m temperature
anomalies exceeding 10F through the late week, we can expect a
warm and dry Christmas.

&&

.AVIATION...(For the 12Z TAFS Through 12Z Monday Morning)
Issued At 403 AM MST Sun Dec 22 2024

VFR conditions are expected to persist through the period. Breezy
northwest winds will likely develop in the 15-18z time frame
across western and south central SD, with some gusts to around
30-35 kt possible through 22z. Winds will diminish by around 00z.

&&

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

$$

DISCUSSION/KEY MESSAGES...Wong
AVIATION...Sherburn