Winner, South Dakota 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

460
FXUS63 KUNR 060814
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
214 AM MDT Fri Jun 6 2025

.KEY MESSAGES...

- Some dense fog this morning mainly east of the Black Hills
- Isolated/scattered showers/thunderstorms this afternoon/evening
  and Saturday afternoon/evening
- Warmer/drier Sunday through Tuesday
- Active southwest flow developing Wednesday through the end of
  next week

&&

.DISCUSSION...(Today Through Thursday)
Issued at 208 AM MDT Fri Jun 6 2025

08z surface analysis had weak high over the CWA with
light/variable winds. Antecedent moisture and mostly clear skies
allowing fog/stratus (per METARs/nighttime microphysics RGB) to
develop early this morning, particularly east of the Black Hills
where a Dense Fog Advisory has been hoisted through 15z. Water
vapour loop had upper trough from Hudson Bay to CA with a
shortwave over the ID/MT/WY border, which will affect the area
later today.

Early this morning, areas of Dense Fog will affect the western SD
plains east of the Black Hills. Will continue to monitor if
expansion is needed.

Rest of today/tonight, ID/MT/WY shortwave slides southeast into
the central plains. Main forcing southwest of the CWA, but diurnal
heating will support 250-500J/kg mean SBCAPE from the Black Hills
south/southwest. North end of shortwave combined with terrain
will be enough for isolated/scattered afternoon/evening
convection. Shear is relatively weak with CAMs not painting any
concerning strength to updrafts. Temperatures will be near
guidance.

Saturday, fast-moving upper low over central Canada drags a cool
front through the CWA with 2-4mb/3hr pressure rises and 20-40kt
850mb winds. Breezy/windy spots (NBM 20-40% chance >45mph gusts)
foreseen. Mean SBCAPE along cool front ~500J/kg with increasing
0-6km bulk shear. Wouldn`t be surprised to see a few strong storms
over the far northern reaches of our CWA, but best combination
further northeast, which is inline with SPC HREF portrayal/Day 2
Outlook. Temperatures will be near guidance and much closer to
summer than recent days.

Sunday through Wednesday, upper ridge builds from the Rockies
into the northern Plains. Thermal ridge perks up for
Tuesday/Wednesday with highs careening into the 80s. Upper trough
develops over the western CONUS for the end of the week creating
southwest flow over the northern Plains. If enough moisture
becomes available, suspect active/severe weather season will
begin given subjective pattern recognition and a hint from CSU MLP
guidance. Most ensemble guidance supports temperatures slightly
above normal.

&&

.AVIATION...(For the 06Z TAFS Through 06Z Friday Night)
Issued At 952 PM MDT Thu Jun 5 2025

In the wake of afternoon/evening showers, areas of BR/FG are
developing over the western/central SD plains and far
northeastern WY. MVFR to localized LIFR conditions have already
materialized, with these conditions expected to expand through the
night. Dense fog and accompanying VLIFR conditions may develop
over portions of the west central SD plains by 09z and persist for
several hours. Most significant reductions to vsbys are expected
to remain east of KRAP, and upper-level clouds arriving from the
west may disrupt fog disruption entirely in and around the TAF
site. However, a brief period of LIFR conditions cannot be ruled
out.

Improvement to VFR conditions is expected area-wide by around 15z,
but additional SHRA/TSRA may lead to reduced cigs/vsbys again
tomorrow morning and afternoon.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...Dense Fog Advisory until 9 AM MDT /10 AM CDT/ this morning for
     SDZ002-013-014-030>032-042>044-046-047-049-073-076>078.
WY...None.
&&

$$

DISCUSSION/KEY MESSAGES...Helgeson
AVIATION...Sherburn