887
FXUS65 KRIW 011531
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
931 AM MDT Mon Jun 1 2026

.KEY MESSAGES...

- Isolated showers and/or virga and a few rumbles of thunder are
  possible (20% to 30%) this afternoon across much of the area,
  with northwestern Wyoming and the Wind River Mountains having
  the greatest potential. Gusty 40 mph outflows are possible
  with showers/virga.

- Temperatures warm into the 70s and 80s each afternoon this
  week, with highs approaching 90s by Saturday. Isolated
  afternoon shower and thunderstorm chances on Thursday across
  northern Wyoming.

- Widespread elevated fire weather conditions are expected each
  day due to low relative humidity values around 10 to 15
  percent.

&&

.DISCUSSION...
Issued at 211 AM MDT Mon Jun 1 2026

The first lobe of the trough spinning across the NW US has
shifted northward into Montana, taking along with it the showers
from yesterday. Another shortwave rotates through during the
day today, getting pulled northward into yesterday`s wave. This
wave is already noted on local radars as high based
showers/virga moving into far SW WY this morning. Moisture will
be notably lower closer to the surface across the region, with
the only areas where humidity remains above 25% would be the
highest elevations of the NW mountain ranges. This combined with
today`s wave being weaker than yesterday`s will limit actual
accumulation chances to 20% or less, again focused exclusively
on the higher elevations.

Tuesday bears some more watching as short-range models have
been hinting at some thunderstorm activity with another weak
wave shifting through the state. The wave isn`t all that
notable, but a more defined moisture boundary across central WY
may become the focus for thunderstorms for greater Natrona and
Johnson Counties during the afternoon. With temperatures
jumping into the low to mid 80s, the strength of any capping
inversion would be the main factor on where thunderstorms would
initially fire before shifting into eastern WY. Right now the
placement of these features is not conducive at the same time
for convection for central WY, but any adjustments on timing may
need an increase of PoPs during the afternoon.

Wednesday sees weak ridging shift into western WY, settling
convection down for the day, and bringing temps back into the
70s and 80s. Another wave sweeping by across Montana brings
another chance for showers and thunderstorms across the
northern half of the state, before ridging return for late week
into the weekend.

&&

.AVIATION /12Z TAFS THROUGH 12Z TUESDAY/...
Issued at 516 AM MDT Mon Jun 1 2026

Cloud cover this morning remains mainly approaching midlevel
deck moving in from the southwest across KBPI/KPNA/KRKS, running
SCT to BKN around 6000 to 8000 feet. A couple of these clouds
are producing a brief raindrop or two, but are not expected to
have impacts this morning. Some isolated shower activity is
possible again this afternoon in the vicinity of western
mountains, but will be much more isolated than yesterday. Most
showers will have difficulty moving away from higher peaks, so
afternoon impacts at local airports either side of the Divide
will be minimal. Best chance for any precipitation would be in
the vicinity of KPNA late this afternoon. Any showers that do
form would produce locally gusty winds from the southwest.
Outside of any showers, southwest winds gusting 25 to 30 kts are
expected from KRKS to KCPR. Winds and any showers will decrease
quickly near sunset.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

DISCUSSION...Straub
AVIATION...Straub