617
FXUS63 KUNR 091711
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1111 AM MDT Fri Oct 9 2026

.KEY MESSAGES...

- Above normal high temperatures continue through Saturday
  afternoon.

- Elevated to near-critical fire weather conditions, especially
  Friday and Saturday.

- Pattern change early next week, resulting in much cooler
  temperatures and chances for precipitation.

&&

.UPDATE...
Issued at 941 PM MDT Thu Oct 8 2026

03z surface analysis had frontal boundary over eastern MT/WY.
Water vapour loop had flat ridge over the Rockies, which will
amplify slightly for Friday/Saturday. This will push frontal
boundary east as a warm front late tonight/Friday with deep
boundary layer mixing behind it. Result will be gusty
southwesterly winds over the southern half of the CWA Friday and
perhaps Saturday. Temperatures will approach record highs both
Friday and Saturday given forecast soundings and downslope lower
tropospheric flow. Cold front slips in Saturday night with much
cooler temperatures for Sunday along with some PoPs.

&&

.DISCUSSION...(This Afternoon Through Wednesday)
Issued at 1143 AM MDT Thu Oct 8 2026

The current forecast has a little bit for everyone. For those who
like the summer-time weather, you`ll enjoy the first part of the
forecast. For those who are looking forward to fall-like weather,
you will like the second part of the forecast.

Friday and Saturday will continue the sunny skies and warm, well
above normal high temps. Expected highs are in the 80s to low 90s
with gusty southwest winds. Elevated to critical fire weather
conditions are likely through Saturday due to low RH and gusty
winds, more information can be found in the FIRE WEATHER section
below.

After Saturday, a change in the weather pattern will happen. Upper
level winds will swing to the west/southwest as a trough of low
pressure deepens over the Pacific northwest. And that low is
projected to track southward along the coast before kicking
eastward toward the the central US. That pattern change will bring
much cooler weather to the area, high temps will drop to the 50s
and 60s and low temps will drop to the 30s and 40s.

This change will also bring back the rain chances. The first
round will begin to move into the far western CWA zones late
Saturday with PoPS lingering into Monday night for the entire CWA.
If the previously mentioned low`s track doesn`t change, then a
break in the rain is likely Tuesday before another round of rain
moves into the area from the southwest Tuesday night with chances
lasting through next Thursday. While model ensembles are still
trying to hint at the snow potential with each round of precip,
the bulk of the model evidence shows that rain is the more likely
precip type.

&&

.AVIATION...(For the 18Z TAFS Through 18Z Saturday)
Issued At 1109 AM MDT Fri Oct 9 2026

VFR conditions are expected through the TAF period.

Gusty southwest winds will persist through the period for
northeast Wyoming and portions of southwest and south-central
South Dakota, with gusts reaching 25-35kts.

&&

.FIRE WEATHER...
Issued At 1143 AM MDT Thu Oct 8 2026

Elevated fire weather conditions are being reported over
northeastern Wyoming into western South Dakota as of this writing
around midday. This afternoon, minimum RH values down to 10-20%
are likely but wind speeds will be on the lighter side.

Near-critical to critical fire weather conditions are expected
Friday over the southwestern reaches of the CWA with Min RH values
down to 10-20% with gusty west/southwest winds upwards of 30 to 35
mph. The Fire Weather Watch has been upgraded to a Red Flag
Warning for the northeastern WY plains, far southwestern SD, and
the foothills.

Saturday will bring near-critical fire weather conditions again
with afternoon RH`s drop to 15-20% and gusty southwest winds.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...Red Flag Warning until 8 PM MDT this evening for SDZ320>327-329-
     332.
WY...Red Flag Warning until 8 PM MDT this evening for WYZ314>318.
&&

$$

UPDATE...Helgeson
DISCUSSION...GS
AVIATION...Schultz
FIRE WEATHER...GS