159
FXUS63 KUNR 052304
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
404 PM MST Wed Feb 5 2025

.KEY MESSAGES...

- Areas of light snow this afternoon and early evening, little to
  no accumulations expected.

- Winter system moves in late Thursday, bringing widespread snow
  accumulations through Saturday morning.

&&

.DISCUSSION...(This Evening Through Wednesday)
Issued at 208 PM MST Wed Feb 5 2025

Current Water Vapor and upper air models show southwest flow with
a weak wave over the Dakotas this afternoon. Surface analysis
shows low pressure over eastern Wyoming, with frontal boundary
stretching east along the SD/NE border. Temperatures currently
range from around 10 in northwestern SD to the mid 40s in
southwestern SD.

Frontal boundary today has set up a bit further south than
originally expected, resulting in the sharp temperature gradient
in southern SD. Temperatures in the 40s to low 50s over fall river
and Oglala counties, while Pennington county is seeing
temperatures in the teens to upper 20s. Shortwave energy has
sparked some light snow in northwestern SD that will migrate east
through early this evening. Dry conditions are then expected
until this larger system moves into the region later Thursday.

Upper low moves over the Rockies and into the northern plains
later Thursday into Friday. Southwest flow ahead of it will promote
increasing isentropic lift along tight low level baroclinic zone.
QG/frontogenetic forcing line up nicely supporting west/east
banded snow field. Still some guidance discrepancy, with the NAM
and European trending further north, while the GFS paints the
highest QPF over the northern third of SD. Ensemble guidance
trends a bit further north as well, with a bit smaller amounts
forecast than previous runs. Current LREF probability of 4" or
more snowfall shows a wide swath of 40-60% chance for areas north
and east of the Black Hills, whereas the probability of 6" or more
drops down to 10-20%. Still enough uncertainty and after
collaborating with neighboring offices, will hold off on potential
Watch for the overnight shift.

Not much of a pattern change as we move into next week, with highs
over the weekend into early next week generally below normal and
periodic chances for some light snowfall over the area.

&&

.AVIATION...(For the 00Z TAFS Through 00Z Thursday Evening)
Issued At 402 PM MST Wed Feb 5 2025

AREAS of MVFR ceilings will persist across parts of northeastern
Wyoming and western South Dakota through tonight. Local IFR
ceilings are possible near the Black Hills. VFR conditions
expected for the area on Thursday. .

&&

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

$$

DISCUSSION/KEY MESSAGES...Dye
AVIATION...7