Winner, South Dakota 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

031
FXUS63 KUNR 042355
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
555 PM MDT Mon Aug 4 2025

.KEY MESSAGES...

- Severe storms possible this afternoon and evening across the
  Black Hills area and portions of southwestern South Dakota.

- Warming temperatures Tuesday and Wednesday, hot temperatures
  Thursday. Highs in the mid 90s to low 100s Thursday.

- Cold front moves through late Thursday and Thursday night.

&&

.DISCUSSION...(This Evening Through Monday)
Issued at 225 PM MDT Mon Aug 4 2025

Upper level analysis has a ridge centered over the western High
Plains with a trough over the Pacific Northwest and down through
the Mississippi River Valley, resulting in a southwest flow
pattern across the forecast area. At the surface, a trough
extends down the east side of Bighorns and a boundary is oriented
east to west across northwestern South Dakota. Radar is showing
some storms firing over the Bighorns with some high based
convection over the boundary in northwestern South Dakota, while
latest satellite imagery has some congested CU along the west side
of the Black Hills.

For this afternoon and evening, expect to see some storms develop
over the Black Hills and across the higher terrain in Wyoming.
Dew points are mainly 50 to 55 degrees, with temps in the 80s.
Thus, storms will likely be high based. CAMs are all over the
place, but with moderate deep layer shear, CAPE of 1500-2500 J/kg,
and Bulk Shear greater than 40kts, could have a few isolated
supercells anywhere from southeast Montana down through
southwestern South Dakota. Main threat for the storms would be
strong winds and hail.

Another round of nocturnal convection is possible across the
western South Dakota Plains tonight as positive theta-e advection
develops ahead of the next shortwave coupled with the low level
jet. Showers/storms will linger into Tuesday morning.

On Tuesday the surface low over southeastern Montana will shift
into southwestern/south central South Dakota as a strong upper
wave pushes across Montana and clips the northern portion of the
forecast area. A few storms will be possible and any storm that
does develop could be strong to severe.

For Wednesday, the ridge continues to build, but models show a
wave trying to initiate convection across southwestern South
Dakota. Have added some low end pops to account for this.
Temperatures will be warm, with highs ranging from the mid 80s to
mid 90s.

Thermal ridge passes over the area Thursday, leading to hot
temperatures in the 90s to low 100s. A cold front will push
through Thursday afternoon and overnight, leading to a good
chance for storms late Thursday and Friday.

&&

.AVIATION...(For the 00Z TAFS Through 00Z Tuesday Evening)
Issued At 544 PM MDT Mon Aug 4 2025

We`ve seen some high based showers move into Campbell county out
of north central WY, so did add a vcsh mention to the first few
hours of the TAF at GCC. This isn`t the greatest TS environment
out there, so we`re not expecting anything significant out of
those radar returns moving into northeast WY. Over southwest
SD/northwest Neb we`ve seen a couple of stronger cells develop
this afternoon. The HRRR has been hinting at storms becoming more
widespread over southeast WY (coming off the Laramie Range), with
a forward propagating MCS going across northern Neb this evening,
but this would stay south of RAP. Otherwise, for the rest of the
night we will see the LLJ increase in strength over western SD, so
this could help spark a shower or two, but confidence in showers
occurring is too low at the moment to include that threat in
either TAF. Overnight, we will see low level moisture increase,
with a threat of some low level stratus developing with upslope
flow coming into the Black Hills. For now, added a SCT030 group to
RAP to cover this potential and is something we`ll have to keep
an eye on tonight. For Tuesday, there will be a surface trough and
convergence zone across western SD, but h7 temps will be up
around 12C, so there will be capping issues to contend with. With
the HRRR and RRFS not developing any convection Tuesday afternoon,
kept any precip potential out of RAP for Tuesday afternoon, but
this will also be something that can`t be ruled out.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...None.
WY...None.
&&

$$

DISCUSSION/KEY MESSAGES...Smith
AVIATION...MPG