340
FXUS63 KUNR 102057
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
257 PM MDT Thu Sep 10 2026

.KEY MESSAGES...

- Hot and dry conditions continue for most of the region today and
  Friday, before trending cooler and more moist for the weekend.

- Elevated to near-critical fire weather conditions continue to
  result, with a RED FLAG WARNING now issued from Weston County
  down across the southwestern South Dakota plains/southern Black
  Hills Friday as increasing winds overlap the dry conditions.

- Next organized storm system remains expected this weekend, with
  the best chance of showers Saturday night through Sunday night.

&&

.DISCUSSION...(This Evening Through Thursday)
Issued at 257 PM MDT Thu Sep 10 2026

A focus on hot, dry, and breezy conditions with attendant fire
weather concerns today into Friday quickly switches over to a
fresh storm system for the weekend with increasing moisture and
decreasing temperatures. More on the fire side of things in the
FIRE WEATHER section below.

No risk of a shower anywhere today. High resolution models are
hinting at cloud buildups and perhaps a few showers as early as
late Friday afternoon into Friday night, but instability (outside
of DCAPE) will be extremely limited and the low-levels will still
lean quite dry per model forecast soundings and HREF means. It`s
possible this activity manifests as more virga than bonafide
showers with little rainfall reaching the ground. That said,
broadbrushed light PoPs across much of the CWA (especially west of
a line from Faith to Pine Ridge) Friday evening to cover any
development, with PoPs focusing more north of Gillette and Rapid
City up to the MT/ND borders overnight into Saturday morning.
Breezy conditions are also forecast Friday as the pressure
gradient tightens and a fairly diffuse cool front moves across the
region from the northwest, shifting winds from the west to north
with time. Gusts as high as 30-40 MPH will be possible across much
of the region.

The potential for showers will increase much more Saturday night
and Sunday...but as we often see with guidance on these systems
as they get closer in time, the potential for substantial
rainfall has trended down. Storm totals may only reach a few
hundredths of an inch across northeastern Wyoming...to 0.10" or
so across the Black Hills and Rapid City...to perhaps 0.50" in our
far eastern counties across the central South Dakota plains. The
magnitude of our cooldown has also moderated (sorry Fall
fans!)...with high temperatures Saturday, Sunday, and Monday now
expected to generally hold in the 70s (instead of 60s) outside of
higher terrain in the Black Hills. Breezy conditions are possible
Sunday and Monday, especially across the northwestern South Dakota
plains. Generally drier conditions are expected by Monday and
Tuesday, although broad troughing to our west/southwest and
precipitation forecast to our south across Nebraska suggest
somewhat low confidence at this juncture.

&&

.AVIATION...(For the 18Z TAFS Through 18Z Friday)
Issued At 1109 AM MDT Thu Sep 10 2026

VFR conditions are expected through the TAF period.

Gusty northwesterly winds will develop across western South
Dakota late Friday morning (~11/15z), with gusts up to 30 to 35
kts. These winds will impact KRAP late in the TAF period.

&&

.FIRE WEATHER...
Issued At 257 PM MDT Thu Sep 10 2026

The hottest and driest conditions of the week are in progress
today, with minimum afternoon relative humidity values now
approaching their forecast lows of 8-18 percent and high
temperatures reaching the low 90s. The limiting factor for
reaching critical thresholds today are the winds, with gusts
generally holding at 15-25 MPH. Very poor overnight RH recovery
remains expected tonight into Friday morning from the Black Hills
and Fall River County area westward across northeastern Wyoming,
with RHs only increasing to 25-35 percent. Friday...the hot
temperatures and low RH values will start to moderate a bit from
the northwest as a somewhat diffuse cool front crosses into the
region, but will remain similarly hot/dry south and east of the
Black Hills overlapping with winds increasing to 15-25 MPH with
gusts 30-40 MPH across most of the region...gradually shifting
from west to north over the course of the day due to the
aforementioned front. A RED FLAG WARNING has now been issued
where these winds will overlap with lingering driest conditions...
generally from Weston County down across the southwestern South
Dakota plains and southern Black Hills from 1 PM to 7 PM. NBM RH
values are running a bit high everywhere compared to nearly all
other sources of guidance including ensembles, in addition to some
uncertainty as to the exact timing and impact of the front coming
in from the northwest. Nudged the RH forecast a bit lower across
southern/eastern portions of the CWA with this in mind. Grassland
Fire Danger will range from Very High to Extreme across most of
the region, especially in response to the increased winds.

High resolution models are hinting at cloud buildups and perhaps
a few showers late Friday afternoon into Friday night, but
instability will be extremely limited and the low-levels will
still lean quite dry per model forecast soundings and HREF means.
It`s possible this activity manifests as more virga than bonafide
showers with little rainfall reaching the ground. Wetting rains
are certainly not expected at this time. That said, broadbrushed
light PoPs across much of the CWA (especially west of a line from
Faith to Pine Ridge) Friday evening to cover any development, with
PoPs focusing more north of Gillette and Rapid City up to the
MT/ND borders overnight. The potential for showers will increase
much more Saturday night and Sunday in association with our next
approaching low pressure system, with the weekend generally
trending cooler and more moist. That said, total weekend QPF
totals are currently only expected to range from a few hundredths
of an inch across northeastern Wyoming to perhaps 0.50" over the
central South Dakota plains. Watch for potentially breezy
conditions looking ahead to Sunday and Monday...especially across
the northwestern South Dakota plains.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...Red Flag Warning from 11 AM to 7 PM MDT Friday for SDZ321-322-
     325-326-332-333.
WY...Red Flag Warning from 11 AM to 7 PM MDT Friday for WYZ317.

&&

$$

DISCUSSION...KSmith
AVIATION...Schultz
FIRE WEATHER...KSmith