498
FXUS63 KUNR 110413
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1013 PM MDT Wed Jun 10 2026

.KEY MESSAGES...

- Very windy conditions behind a cold front for Thursday

- Unsettled weather through the weekend per a series of fronts
  with up/down temperatures trending coolish for the weekend.

- Near critical fire weather conditions Friday.

&&

.UPDATE...
Issued at 1013 PM MDT Wed Jun 10 2026

Clouds are increasing as a strong vort lobe moves in from the west.
Surface obs show temps in the 60s across the western SD plains...and
40s/50s over NE WY through NW SD where a cold front has pushed
through. The front will continue through the CWA overnight, bringing
cooler max temps on Thursday. Radar shows light post-frontal showers
across NW SD, and more extensive shower development is expected late
tonight through Thursday morning as the next strong wave moves in.
Increasing winds are also expected late tonight through Thursday.
Latest guidance shows the strongest gusts early in the morning when
boundary layer winds peak at 45kt before gradually decreasing
through the early/mid afternoon. Downsloping across the southern
Black Hills (primarily Fall River County) may allow these gusts to
reach foothills locations earlier in the morning before the rest of
the western SD plains mix out enough. Will keep the Wind Advisory
going with no changes needed.

&&

.DISCUSSION...(This Evening Through Wednesday)
Issued at 1228 PM MDT Wed Jun 10 2026

18z surface analysis had weak high over the CWA. 0.5km visible
satellite loop had CU field starting to increase in size per
daytime heating/weak buoyancy. Might see a few shra/TS during peak
heating this afternoon/early evening. Water vapour loop had mean
upper trough over central Canada, extending into the northern
Plains. Distinct shortwave trough rotating southeast into MT per
water vapour, which is the main forecast concern.

Shortwave trough whips through the northern plains overnight into
Thursday morning pushing a cold front through the CWA. Decent QG-
forcing should assist shra/isolated TS moving across the area.
Isallobaric forcing modest, but it will be accompanied by steep
low-level lapse rates and good subsidence for Thursday which
should tap into 25-40kt mixed boundary layer. Showers could
enhance. NBM looks rather strong for peak wind gusts (~60mph)
given forecast Bufkit momentum transfer. Have shaved some speed
from prescribed forecast wind elements. Still, very good chances
(50-90% chance >45mph gusts) for Wind Advisory gusts behind the
cold front for the usual areas from K2WX-KRAP and far southwestern
SD. ECMWF EFI guidance paints 80th percentile wind gusts with a
shift of tails contour. Temperatures will be near guidance.

Rest of the forecast looks unsettled as a series of disturbances
traverse the northern plains per northwest flow aloft. Deeper
trough brings PoPs/cooler temperatures for the weekend. Each
front/disturbance will bring gusty winds. There are hints that an
upper ridge may develop for the middle of next week, but
increasing ensemble spreads portend lower confidence.

&&

.AVIATION...(For the 06Z TAFS Through 06Z Thursday Night)
Issued At 1013 PM MDT Wed Jun 10 2026

MVFR/IFR CIGS will move in early Thursday morning across NE WY,
along with rain showers. These showers/low CIGS may reach into the
northern/western Black Hills and NW SD, as well. Showers will end
in the mid/late morning hours, and VFR conditions will move back
in by around 18z. Northwesterly winds will also increase
overnight, and persist into the early afternoon before decreasing.
Gusts up to 45 kt are possible across the NE WY plains and much of
the western SD plains.

&&

.FIRE WEATHER...
Issued At 921 PM MDT Wed Jun 10 2026

Elevated to near-critical fire weather conditions are expected
Friday due to very dry air. Minimum relative humidities in the
teens are expected over northeast Wyoming and much of western
South Dakota south of I-90. At this time where the humidity will
be most critical, winds are not expected to be strong enough to
reach critical fire weather thresholds.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...Wind Advisory from 3 AM to 5 PM MDT Thursday for SDZ001-002-012-
     013-027-031-041-072-073-075-078.
WY...None.
&&

$$

UPDATE...13
DISCUSSION/KEY MESSAGES...Helgeson
AVIATION...13
FIRE WEATHER...13