867
FXUS63 KUNR 161116
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
516 AM MDT Thu Jul 16 2026

.KEY MESSAGES...

- Hot temperatures continue through the weekend with elevated to
  near critical fire weather conditions.

- Isolated thunderstorms Thursday and Friday - mainly Black Hills
  and northeast Wyoming - with scattered thunderstorms this
  weekend across the entire area.

- Unsettled and cooler next week.

&&

.UPDATE...
Issued at 1015 PM MDT Wed Jul 15 2026

A couple of isolated showers/storms have tried to develop along a
sfc trof currently located across NE WY this evening. Can`t rule
out isolated shower activity overnight across NE WY but confidence
too low to include in PoPs at this time. Otherwise, the extended
period of very hot conditions continues to be the main forecast
concern over the next few days. Highs in the upper 90s to 100s
expected across much of western SD and northeastern WY through the
weekend as upper level ridge dominates the upper level pattern
into the weekend.

&&

.DISCUSSION...(This Evening Through Wednesday)
Issued at 1243 PM MDT Wed Jul 15 2026

High pressure continues to be centered over the Central Great Plains
with water vapor imagery showing moisture streaming into the Desert
Southwest up into the Rockies. At the surface, an area of low
pressure is centered over southeast Montana with a warm front
extending through southern North Dakota, a lee trof along the
Bighorns, and a cold front extending into northwest Wyoming.
Temperatures at 19Z are in the 90s, with a few spots around 80 in
the higher Black Hills. Winds are generally south to southeast at
5 to 15 mph.

The cold front will slowly slide into the forecast area tonight
as the surface low pushes into southwestern North Dakota and
eventually into south-central North Dakota by Friday morning. The
main impacts with the cold front will be limited. Winds behind the
front will be northerly, high temperatures will be a degree or
two cooler, and there will be a chance for afternoon and evening
thunderstorms.

Low level moisture begins to increase Thursday morning as the upper
ridge begins to slowly break down. The increase in moisture combined
with an increase in instability may allow for isolated thunderstorms
behind the cold front on Thursday and Friday. There will be greater
chances for storms this weekend as the upper ridge shifts eastward,
monsoonal moisture streams into the area, some small vorticity maxes
move through the flow, and modest ascent along the frontal
boundary.

Models differ slightly on how fast the upper ridge collapses and the
positioning of the surface fronts this weekend. However, the overall
pattern will lead to a chance for scattered storms this weekend,
with unsettled weather and cooler temperatures next week.

&&

.AVIATION...(For the 12Z TAFS Through 12Z Friday Morning)
Issued At 514 AM MDT Thu Jul 16 2026

VFR conditions expected through the period. Isolated/scattered
gusty thunderstorms may occur over the Black Hills/northeastern
WY this afternoon/evening, but not enough confidence they`ll hit
the TAF sites, so have not introduced to the forecast.

&&

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

$$

UPDATE...Wong
DISCUSSION...MLS
AVIATION...Helgeson