Gillette, Wyoming 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

145
FXUS63 KUNR 160451
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
1051 PM MDT Fri May 15 2026

.KEY MESSAGES...

- Warm and breezy with near-critical fire weather conditions
  through Saturday
- Pattern change Saturday night through Monday will result in
  showery, cooler weather with potential active/severe
  thunderstorms over south-central South Dakota Sunday
  afternoon/early evening

&&

.UPDATE...
Issued at 934 PM MDT Fri May 15 2026

03z surface analysis had weak high from MT into the Dakotas with
weak return flow starting across the far southwest given
increasing easterly component to winds. Few radar returns have
popped up over northwestern SD with a few bumps per IR satellite
loop (under right entrance region of 100kt jet), so have added
isolated sprinkles for late this evening. Water vapour loop has
westerly flow aloft over the northern Plains with jet
streak/trough starting to amplify flow over the northwest CONUS.
This will be the main weather maker into early next week.

Broad strokes of current forecast in decent shape. Another warm
day tomorrow as thermal ridge changes little and upper trough
develops over the northern Rockies. Initial impulse ahead of it
saunters into the plains with 35-45kt low level jet Saturday
night over western SD. Low level theta-e advection fairly robust
with weak MUCAPE developing. Showers/TS will breakout Saturday
evening, moving northeast through Sunday morning. As first
impulse departs, it will push a cold front through the CWA.
Position of cold front Sunday afternoon/evening will determinate
where moderate buoyancy/strong shear regime and resultant severe
thunderstorm potential develops. SPC HREF only out to early
Saturday morning right now, but some of the 00z CAMS suggest main
action will be east of the CWA. Confidence in frontal position is
low, however, with Saturday night convection playing a big role in
how fast/slow the cold front moves through. Upper trough then
approaches for Sunday/Monday with modest QG-forcing, increasing
PWATs, and bands of 800-600mb frontogenesis. Good setup for
beneficial rains for parts of the CWA. Latest ensemble guidance
trend has been further east for heaviest QPF band, which is
reflected in latest QPF forecast. Cold enough in the Black Hills
for some refreshing snow up high.

&&

.DISCUSSION...(This Evening Through Friday)
Issued at 1230 PM MDT Fri May 15 2026

A pattern change is still expected this weekend. For now, we are
still holding on to near-critical fire weather through Saturday.
Saturday night into early next week, the rain chances return to
the area with cooler temps sliding in from the north.

To start the forecast, zonal flow in the upper levels will give
very little change to our weather. So highs in the 70s and 80s are
expected Saturday, overnight lows tonight through Saturday night
will be in the 30s to 40s. Skies will be clear to mostly clear
with clouds increasing from the west Saturday. And with not much
moisture in the area, afternoon relative humidities will be low,
at around 10 to 20%. Sustained winds will top out around 10 to 25
mph and gusts will reach near 20 to 40 mph, strongest winds in the
SD plains northeast of the Black Hills. Decided to hold off on
issuing a Red Flag Warning because the strongest wind speeds look
to happen where relative humidity will be near 20%. And where the
RH values bottom out near 10 to 15%, winds are forecast to be on
the lighter side. These forecast conditions will be monitored
closely and if needed, warning products will be issued.

Sunday and early next week, a passing upper level trough and
surface cold front will bring some very different weather to NE WY
and W SD. For starters, Saturday night into Sunday, showers and
thunderstorms are likely. Some of those thunderstorms have the
possibility to be strong to severe in south-central SD. The SPC
has highlighted this area with a Marginal risk.

Sunday could play out to be an interesting weather day. It`s
looking like a surface low will develop near the NE-WY-to-Black-
Hills area Sunday morning and track eastward. As it does, it will
develop a cold front that will swing to the southside of the low.
As the cold front slides east, thunderstorm development is
possible. The timing of the cold front will highly influence where
the strongest storms will be. A slower moving front will lead to
more storms in western SD while a quicker moving front will lead
to most of the thunderstorm action happening to the east of the
CWA. For now, it`s looking like a quicker moving front is the most
likely scenario but uncertainty is high at this time.

As the cooler air slides into the area behind the cold front,
most of the area has a decent chance of seeing rain but higher
elevations of the Black Hills have a good chance of seeing
accumulating snow Sunday night into Monday. At this times, upwards
of 3 to 6 inches is possible. Stay tuned for updates.

For the rest of next week, PoPS diminish and temps warm back to
the 60s and 70s for highs.

&&

.AVIATION...(For the 06Z TAFS Through 06Z Saturday Night)
Issued At 1050 PM MDT Fri May 15 2026

Conditions will remain VFR through tonight. Gusty southerly flow
will ramp up Saturday afternoon ahead of elevated storms moving
through the area around 02Z Sunday. These scattered showers may
have gusty and erratic outflows.

&&

.FIRE WEATHER...
Issued At 1230 PM MDT Fri May 15 2026

Warm, dry, and windy conditions with receptive fuels will
continue to support near-critical conditions to most of western
SD through Saturday.

The gusty winds from today will weaken this evening but RH values
will see poor overnight recovery. Dry and breezy weather will
stick around through Saturday. That being said, as of now, it`s
looking like the winds will be below thresholds where RH is low
enough, so decided to hold off on issuing red flag warning for
now.

Cooler with shower chances early next week, leading to a break in
fire weather concerns although the best chance for wetting rains
will be east of the area.

&&

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

$$

UPDATE...Helgeson
DISCUSSION/KEY MESSAGES...GS
AVIATION...Schweigert
FIRE WEATHER...GS