575
FXUS63 KUNR 171120
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
520 AM MDT Fri Jul 17 2026

.KEY MESSAGES...

- It will remain hot through the weekend with elevated to near
  critical fire weather conditions.

- Chance for isolated to scattered thunderstorms Friday, mainly
  across the Black Hills and parts of northeast Wyoming.
  Thunderstorms become a little more numerous this weekend.

- Slightly cooler conditions finally look to return for next
  week.

&&

.UPDATE...
Issued at 939 PM MDT Thu Jul 16 2026

Hot weather continues with temperatures across much of the CWA in
the mid to upper 90s to low 100s through this weekend. Have opted to
extend Heat Advisory through Sunday evening due to the prolonged
nature of the heat. With temperatures each night staying in the
upper 70s to low 80s until well into the overnight hours, not much
relief expected overnight.

Isolated/scattered shower and storm activity along a stationary sfc
front/trof draped across northeastern WY into northwestern SD will
diminish through the late evening hours. This boundary will slowly
push to the south through the day tomorrow with enough instability
for scattered storms to develop over the Black Hills and
northeastern WY in the afternoon. Deep layer shear is lacking with
the sluggish upper flow so while a few strong storms can`t be ruled
out, organized severe weather isn`t expected.

&&

.DISCUSSION...(This Afternoon Through Wednesday)
Issued at 1135 AM MDT Thu Jul 16 2026

18Z upper level analysis has persistent ridge across the central
CONUS with upper low spinning off the Pacific Northwest coast.
Skies are mostly clear across the forecast area, with some
isolated thunderstorm development occurring over the Black Hills.
At the surface, there is a weak cool front that has moved into
northwestern SD and northeastern WY, evident by a shift to light
northerly winds in those areas. Temperatures at noon across the
forecast area range from the 80s along and west of the cool front,
to the low to mid 90s east of the front.

Temperatures are still expected to top out in the mid 90s to low
100s across the area this afternoon, warmest east of the Black
Hills. Isolated storms are expected across the Black Hills and
parts of northeast Wyoming this afternoon, with some storms
persisting into the evening hours. Lows tonight will be in the 60s
to lower 70s.

Upper ridge remains nearly stationary through Friday with
temperatures similar to today. Weak cold frontal boundary will
slowly drop through the area, with light northeast to east winds
expected across the area. Models/CAMS are showing a little better
chance for scattered thunderstorms over the Black Hills and
northeast Wyoming Friday afternoon, with mainly dry conditions
persisting across the SD plains. Very mild temperatures persist
into the overnight hours.

Upper ridge shifts a bit east over the weekend. Very warm
temperatures will persist across the area, but storm chances
become a little better as upper flow becomes more westerly with
some weak impulses crossing the Northern Plains.

West to northwest flow becomes a little stronger early next week.
This will lead to slightly cooler conditions and a little more
unsettled weather for next week.

&&

.AVIATION...(For the 12Z TAFS Through 12Z Saturday Morning)
Issued At 518 AM MDT Fri Jul 17 2026

Mainly VFR conditions are expected through the TAF period.
Isolated/scattered TSRA will develop this afternoon/early evening
over the Black Hills into northeastern WY. Any storm may contain
local IFR conditions and gusty, erratic winds. Confidence too low
to mention at terminals right now.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...Heat Advisory until 9 PM MDT /10 PM CDT/ Sunday for SDZ001-002-
     012>014-025>027-030>032-041>044-046-047-049-072>078.
WY...Heat Advisory until 9 PM MDT Sunday for WYZ054>056-058>060.
&&

$$

UPDATE...Wong
DISCUSSION...15
AVIATION...Helgeson