016
FXUS63 KUNR 301724
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1124 AM MDT Fri Oct 30 2026

.KEY MESSAGES...

-Cloudy and cool Friday with fog possible on the SD Plains

-Mild and dry most of this weekend

-Unsettled and cooler to start next week with a good chance of
 rain Sunday night into Tuesday, some high elevation snow is
 possible as well

&&

.UPDATE...
Issued at 941 PM MDT Thu Oct 29 2026

Latest nighttime microphysics RGB showed two areas of stratus.
One over NE which is heading north toward the CWA. Another over
central ND, which will expand southwest into the Black Hills
foothills as T/Td spreads converge overnight. This will lead to
patchy/areas of fog primarily on the SD plains. Previous forecast
had things well depicted. Made some minor updates for the latest
timing/coverage. Did lower MaxT for Friday where stratus is not
expected to scatter. Perennially insightful NAM guidance has a
high of 43F for KRAP Friday. NBM guidance 5-10F higher, so didn`t
go wild with lower temperatures. Something to be aware of,
however.

&&

.DISCUSSION...(This Afternoon Through Wednesday)
Issued at 1141 AM MDT Thu Oct 29 2026

Deep upper trough over the PAC NW and western Canada will support
general SW flow into the weekend. Departing impulse giving way to
clear skies today as winds shift easterly behind the sfc
reflection. Expect highs in the 50s and 60s. Southerly flow will
develop tonight and support a push of low level moisture into the
region. This will support low clouds and areas of fog over most of
the SD Plains. Temps will struggle to rise Friday on the SD
Plains with 40s and 50s expected for highs. With clear skies and
better mixing, expect 60s over northeast WY. There is a low chance
for a few showers Friday night toward central SD as a disturbance
skirts the region to the south and forces pos theta-e adv in the
Northern Plains. Low clouds and fog are likely to stick around on
the SD Plains as southerly flow persists Friday night. Winds will
veer in the low levels Sat and allow mix out of low clouds and fog
as drier are mix in. However, mid and upper level clouds look to
increase which could hold temps down a bit. Western CONUS upper
trough will lift out of the western Pac early next week, with
broad lift spreading into the region starting Sunday night. Ample
low level moisture will advect ahead of this system which will
allow for a decent chance of precip on the SD Plains, esp toward
central SD. The best chance for precip will be Monday when the
main trough passes over the region. Very warm system for early
Nov, with mainly rain expected. However, enough cold air may
entrain into the back of the system Monday to allow for some
higher elevation snow across northeast WY and the Black Hills.
This could some support some light snow accums there, esp in the
northern Black Hills. Things will dry out west to east Tues with
cooler conds expected for the rest of the week as NW flow becomes
established.

&&

.AVIATION...(For the 18Z TAFS Through 18Z Saturday)
Issued At 1115 AM MDT Fri Oct 30 2026

Fog will continue to burn off across northwestern SD. A low cloud
deck will remain in place for most of western SD through the day,
as well as portions of northeast WY excluding KGCC. Conditions
will remain mostly unchanged going into tonight. Fog is expected
to develop over parts of western SD Saturday, bringing LIFR
conditions. Clouds decks will drop after about 03Z, followed by
visibilities 1-2 hrs later. These conditions are expected to stay
in western SD, however WY may see cloud bases drop to near MVFR
cigs. For now, have left out low clouds from KGCC but will update
pending future model guidance.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...Dense Fog Advisory until noon MDT today for SDZ001-002-012-078.
WY...None.
&&

$$

UPDATE...Helgeson
DISCUSSION...JC
AVIATION...Schweigert