935
FXUS63 KUNR 281711
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1011 AM MST Fri Nov 28 2025

.KEY MESSAGES...

- Slick travel due to snow/blowing snow expected from two rounds
  of snow through Saturday morning with the highest impacts
  tonight
- 10-20F below normal temperatures this weekend
- Light snow Tuesday/Wednesday

&&

.DISCUSSION...(Today Through Thursday)
Issued at 219 AM MST Fri Nov 28 2025

09z surface analysis had stationary front from central MT through
central CO with weak low over WY. Water vapour loop had upper
trough moving into the northern Rockies with lead 90kt jet streak
zipping across WY. Lift ahead of jet streak over frontal boundary
causing a north/south- oriented band of radar returns over western
SD per KUDX radar loop. Some flurries/light snow reaching the
ground. Effect of upper trough the main concern.

Today/Saturday, upper trough moves east/southeast across the
plains. Surface low moves southeast and deepens as inverted trough
feature slides through the CWA. Initial band of snow per
frontogenesis/moderate 800-600mb theta-e advection will intensify
as it moves east. Not much moisture behind first band with a lull
in precipitation expected, but this will change as upper trough
moves through tonight per moderate QG- forcing/frontogenesis
behind developing cold front trailing surface low. Latest guidance
has upped the ante with regard to forcing/mass output along with
isallobaric forcing behind the cold front. Result is an uptick in
QPF/snow amounts and gusty northerly winds. ECMWF EFI depicts
50-80th percentile snowfall with SPC HREF mean QPF rising compared
to previous ensemble guidance. Not a huge fan of advisory creep,
but feel combination of increased snow on the plains (1 to locally
4 inches) and stronger winds will create a hazardous snow/blowing
snow combination tonight into Saturday morning. Have raised
Winter Weather Advisories to account in collaboration with
surrounding offices. Froude number >1/0-2km RH ~90% for the
northern Black Hills tonight, so will continue headlines there,
but have pushed back timing to be more in sync with latest
guidance and warmish temperatures this afternoon. Speaking of
temperatures for today, didn`t stray too far from guidance over
the southern half of the CWA near warm front, but did drop MaxTs
over northwestern SD. Saturday looks chilly with highs 10-20F
below normal. Sunday will be relatively dry and cold. Some
deterministic guidance depicts snow showers Sunday afternoon, but
ensemble guidance not on board. Left forecast dry for now. Warmer
temperatures are expected Monday ahead of next upper trough that
zips through bringing a chance of light snow Tuesday/Wednesday.
The end of next week will be unsettled with temperatures near
normal.

&&

.AVIATION...(For the 18Z TAFS Through 18Z Saturday)
Issued At 1004 AM MST Fri Nov 28 2025

VFR conditions will become MVFR and IFR late this afternoon and
evening as a storm system moves into the area. Widespread
IFR/MVFR conditions due to snow will be common across the entire
area after 29/03Z.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...Winter Weather Advisory until 11 AM MST Saturday for SDZ001-002-
     014-078.
     Winter Weather Advisory from 5 PM this afternoon to 11 AM MST
     Saturday for SDZ012-013-024>026-031-032-043-072-073.
     Winter Weather Advisory from 8 PM MST /9 PM CST/ this evening to
     11 AM MST /noon CST/ Saturday for SDZ027-030-041-042-044-
     046-047-049-074>077.
WY...Winter Weather Advisory from 5 PM this afternoon to 11 AM MST
     Saturday for WYZ057-060.
     Winter Weather Advisory from 5 PM this afternoon to 8 AM MST
     Saturday for WYZ054>056-058-059.
&&

$$

DISCUSSION/KEY MESSAGES...Helgeson
AVIATION...Smith