684
FXUS63 KUNR 070441
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1041 PM MDT Sun Sep 6 2026

.KEY MESSAGES...

- Critical fire weather conditions over parts of northeastern
  Wyoming and extreme southwestern South Dakota late Monday
  morning through early Monday evening

- Above average temperatures remain in the start of the forecast.
  Afternoon temps will be in the upper 80s to 90s for Monday but
  cooler temps expected midweek.

- Elevated to potentially critical fire weather conditions linger
  for much of next week

- Isolated to scattered thunderstorms are expected through Monday
  morning.

&&

.UPDATE...
Issued at 948 PM MDT Sun Sep 6 2026

03z surface analysis had low over southeast MT with a warm front
into southern ND and a trough into ID. Water vapour loop had deep
southwest flow from the southwest CONUS into the northern Plains.
Several impulses wiggling along the edge of a 130kt jet. Next
impulse traveling through eastern WY, assisting convection as a
forecast 20-35kt low level jet develops ahead of surface low.
Starting to see evidence of that per regional radar loop and KUDX
VWP. Isolated/scattered TSRA will move northeast through the CWA
overnight into Monday morning with general CAM agreement.

Surface low will deepen Monday as upper trough translates
eastward. Cold front trailing low will invade the CWA late with
deep southwest boundary layer mixing ahead of it over northeastern
WY/southwestern SD. Expect very dry to develop ahead of the cold
front with gusty west/southwest winds. Combination will create
critical fire weather conditions, so have issued a Red Flag
Warning to account.

Rest of forecast in decent shape for now with a somewhat cooler
temperatures making an appearance for a couple of days next week.

&&

.DISCUSSION...(This Evening Through Sunday)
Issued at 1202 PM MDT Sun Sep 6 2026

A change in the winds is coming to the area this week. The last
couple of days, we have been under the influence of a large upper
level ridge that has been giving us southwest flow in the higher
parts of the atmosphere. Through tomorrow, an upper level low
spinning over the pacific northwest will kick eastward. This
low will shift upper level winds over the CWA from the southwest
to west. This means passing storm chances, then slightly cooler
temps. And the longer term forecast is hinting at bigger swings in
temps that could mean bigger breaks from the heat.

At the surface, an area of low pressure will develop near north
central Wyoming later today. This low is expected to track
northeast tonight through tomorrow. And as it moves east
tomorrow, north of the CWA, it will swing a cold front through the
area.

Showers and thunderstorms are likely as these changes happen
through tomorrow. For today, storms are expected to pop up over
the Black Hills during the heat of the day and these storms will
move east-to-northeast through the afternoon and evening. At the
same time, more storms are likely to develop to our south and
those will drift northwards later this evening and overnight.
Severe weather can`t be ruled out with hail and strong winds being
the main concerns. The SPC has placed a Marginal risk centered
over the Black Hills and the surrounding plains. Machine learning
severe weather models are also highlighting the same area.

Late tonight into early Monday, the previously mentioned cold
front will slide west to east over the area. pushing any
lingering precip, or new rain/storm development, eastward. Based
on current projections though, the bulk of any rain and showers
tomorrow will be gone by midday with mostly sunny to partly cloudy
skies Monday afternoon. The rest of the week looks dry with the
next round of rain possible next weekend. Once the front pushes
through, westerly winds will pick up some speed. Monday afternoon
winds will be strongest in NE WY at upwards of 20 to 25 mph, gusts
over 30 mph. Then Tuesday, the strongest winds will shift to the
NW SD plains at around 20 to 30 mph, gusts nearing 40 mph.

Lastly, the temperature outlook for this week has some big swings.
Afternoon highs take a dip after today and tomorrow`s highs in
the upper 80s to 90s with Tuesday and Wednesday`s highs in the 70s
to 80s. Highs in the 80s and 90s return Thursday and Friday. Next
weekend could see temps below normal, stay tuned.

&&

.AVIATION...(For the 06Z TAFS Through 06Z Monday Night)
Issued At 1040 PM MDT Sun Sep 6 2026

Isolated/scattered thunderstorms will slowly move northeast across
portions of northeastern WY/western SD tonight, waning from
southwest to northeast Monday. Local MVFR conditions may occur
with any thunderstorm along with gusty, erratic winds. Have added
a PROB30 for KRAP from 07/08-10z as a cluster of storms come out
of eastern WY. Outside of thunderstorms, VFR conditions are
expected with gusty southerly winds, especially on the open
plains.

&&

.FIRE WEATHER...
Issued At 1202 PM MDT Sun Sep 6 2026

Fire weather continues to be a concern with elevated to near
critical conditions likely. Afternoon temperatures in the 80s to
90s to start the week. And very dry weather lingers with minimum
relative humidity down to 10 to 20 percent for the western zones.
And once a cold front pushes through, westerly winds will pick up
with gusts upwards of 25 to 40 mph at times for Monday and
Tuesday. Lighter winds expected for the second half of the week.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...Red Flag Warning from 11 AM to 7 PM MDT Monday for SDZ322.
WY...Red Flag Warning from 11 AM to 7 PM MDT Monday for WYZ314>317.
&&

$$

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