601
FXUS65 KRIW 061907
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
107 PM MDT Sat Jun 6 2026

.KEY MESSAGES...

- Widespread critical fire weather conditions continue through the
  weekend given low humidity, gusty wind, and hot temperatures.

- Chances (10-15%) for very isolated showers and thunderstorms today
  and tonight mainly across northern and western Wyoming.

- Thunderstorm chances become more widespread Sunday (15-40%),
  with a couple of stronger storms possible across the eastern
  Bighorn Basin and Johnson County.

&&

.UPDATE...
Issued at 105 PM MDT Sat Jun 6 2026

Today`s forecast of hot and dry conditions is on track, though
scattered high clouds have delayed heating slightly. Still, peak
temperatures should reach near 100 degrees in portions of the
Bighorn Basin, as well as northeastern Johnson County. There are
currently some weak, isolated showers across northwestern Wyoming,
and there are still indications that there may be additional
development later today as cyclonic flow increases. Critical fire
weather conditions are the more widespread impact given the elevated
southwest wind. Similar concerns will be noted for Sunday, with the
additional threat of more widespread and robust convection as the
trough begins swinging in.

&&

.DISCUSSION...
Issued at 206 AM MDT Sat Jun 6 2026

The long-awaited buckling of the midlevel flow has begun to
strengthen across the western US, and will bring the warmest
day of 2026 to most of the state. H7 temperatures are already
running 12-14C, and will be peaking this afternoon between 16
and 18C, which translates to the sfc as highs in the upper 80s
to the upper 90s. Isolated readings at 100 degrees may be noted
along the lowest elevations of the Bighorn Basin for a few
hours this afternoon. Temperatures aloft will be cooler for NW
WY, which is closer to the incoming trough, which will keep
temps more modest in the 70s this afternoon.

The southwest flow around the approaching trough will be very
dry, and with dry air already at the sfc, will mix well down to
the sfc this afternoon. Wind gusts will reach 35 to 50 mph
through the afternoon, picking up around noon and continuing
into the early evening. Humidity levels will also crash down
this afternoon, staying below 10 percent through the afternoon.
This leads to critical fire weather concerns all day.

Tonight, the advancing trough moves off the PacNW coast into the
Northern Rockies, pushing the heat ridge eastward and opening
up most of the state for increased moisture. There is a hint in
some of the convective models that today`s heating may be enough
to tap the leading edge of the trough to spark a few showers
even into central WY this afternoon, but this will be battling
against the subsidence with the ridge, so this area may be
limited to some increased CU. The better chances for showers
first builds into the NW Parks this evening and overnight as
the first lobe of the trough passes through. The next band then
sets up somewhere in central WY during Sunday afternoon,
influenced by an instability axis aloft. As the trough moves
east, an enhanced area of shear builds into northern WY, which
will also be influenced by terrain shear off the Bighorn Range.
Strongly sheared environment and instability could lead to
thunderstorms quickly strengthening across Johnson County during
the afternoon, with a quickly increasing threat for hail and
very strong winds. SPC has this areas in a slight risk on
Sunday, and will need to monitor for final timing.

Into early next week, the main trough shifts east, putting the
axis along the Rockies for the first half of the week. Right
now, this puts the northern half of the state in a more showery
pattern through most of the upcoming week.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 1114 AM MDT Sat Jun 6 2026

Mostly VFR flight conditions are forecast at all terminals through
at least 18Z Sunday. Winds will quickly increase from the southwest
by 20Z with frequent 25kt to 35kt gusts. The strongest gusts are
forecast at KRKS, KPNA, and KWRL and these three terminals could see
occasional gusts around 40kts. Gusty winds at all terminals will
begin to diminish between 00Z and 03Z Sunday and be 11 kts or less
overnight. Wind quickly increase again from the southwest after 14Z
Sunday at all terminals.

There is 10% chance of a shower at KRKS and KCPR from roughly 23Z
today to 03Z Sunday. Low light rain chances exist across western
Wyoming between 04Z and 09Z Sunday and brings a 30 percent chance of
light rain to KJAC. Isolated to scattered shower and thunderstorm
chances are forecast on Sunday, with a 30 percent chance at KJAC as
early as 15Z Sunday. A heavier shower could result in brief periods
of MVFR visibilities at KJAC. There is potential that KRKS and KWRL
sees an isolated thunderstorm after 18Z Sunday.

Please see the Aviation Weather Center and/or CWSU ZDV and ZLC for
the latest information on icing and turbulence forecasts.

&&

.FIRE WEATHER...
Issued at 105 PM MDT Sat Jun 6 2026

Critical/near-critical fire weather conditions will be widespread
across the area through at least early next week. An incoming system
will also increase the lightning and outflow wind threat starting
Sunday as isolated thunderstorms move northeast across the area. The
near-surface conditions will remain dry, so much of this may be
virga. In addition to the background gusty southwest wind, this
activity could produce strong and erratic wind gusts of 50 to 60
mph.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning until 8 PM MDT this evening for WYZ280.

&&

$$

UPDATE...Myers
DISCUSSION...Straub
AVIATION...Gerhardt
FIRE WEATHER...Myers