Teton Village, Wyoming Weather Forecast Discussion

162
FXUS65 KRIW 071907
AFDRIW
Area Forecast Discussion
National Weather Service Riverton WY
107 PM MDT Sun Sep 7 2025
.KEY MESSAGES...
- Isolated to scattered showers and thunderstorms steadily
  increase in coverage through 4 PM Sunday and persist through
  much of Sunday evening. Locally heavy rain and wind gusts 35
  to 45 mph will be possible with the stronger (10% chance)
  storms, mainly along and west of the Continental Divide.
- Widespread elevated fire weather conditions are expected
  Monday through Thursday, with a focus on Wednesday and
  Thursday. Gusty southwest wind 20 to 35 mph is the primary
  hazard, mainly in southwest and central Wyoming.
- Afternoon and evening showers and thunderstorms are expected
  again Tuesday through Friday, with chances for widespread
  precipitation across the far west beginning Friday.
&&
.UPDATE...
Issued at 107 PM MDT Sun Sep 7 2025
Shortwave energy moving across northern Wyoming has kept extensive
cloud cover and a line of weak showers moving slowly northeast
Sunday morning and early afternoon. The loss of cloud cover behind
this shortwave has already allowed for scattered showers and
isolated thunderstorms to erupt over the northwest mountains as of 1
PM Sunday. Meanwhile to our west, early morning ACCAS has given way
to at least one robust thunderstorm in eastern Idaho. Convection is
expected to gradually fill-in across west-central Wyoming between 2
and 4 PM with enough instability, CAPE 1000 J/kg and LI`s -2 to -4,
to generate stronger convection until 6 PM. Upstream KSLC morning
sounding and early Sunday afternoon derived satellite data indicate
precipitable water values around 0.80 inches, so brief heavy rain is
possible. Storms will be moving easterly around 20kts, so resident
time over any given area should not be long. Otherwise, wind gusts
35 to 45 mph would also be possible. In general, isolated to
scattered showers and thunderstorms occur for all areas through
sunset Sunday. Another round of convection rotates through the
Tetons and Yellowstone between 7 and 10 PM Sunday before weakening
and moving east into the early morning hours Monday. For Monday
afternoon, there is enough mid-level moisture over the western
mountains to help produce isolated convection during daytime heating
late in the day. A few CAMs seem to be catching on to this
possibility, while others and the NBM are basically dry. Low PoPs
were introduced to account for the isolated afternoon convection,
mainly in the Absaroka and Wind River Ranges.
&&
.DISCUSSION...
Issued at 140 AM MDT Fri Sep 5 2025
A broad ridge will be over the Cowboy State today, with subtle
embedded shortwaves moving in from the southwest. These will provide
the necessary lift for more widespread shower and thunderstorm
activity across the CWA this afternoon and evening. High
temperatures this afternoon will be in the upper 70s to upper 80s,
with Johnson County being 10 degrees warmer. Thunderstorms are not
expected to be strong again today, but locally heavy rain could
occur as PWATs increase to around 0.6" to 0.85". This will translate
to dewpoints in the upper 30s to upper 40s across the forecast
area. This will be a 20 degree increase from Saturday for areas
east of the Divide. Additionally, MLCAPE values of 200-500 J/kg
will be in place. The one exception looks to be around the Star
Valley, where MLCAPE values around 1000 J/kg could occur. Any
areas of upper level diffluence are a bit isolated, but one area
looks to coincide over the Alpine-Bondurant area. As such, the
steering flow will remain light so the showers and storms will
be slow moving. This would add to the threat for locally heavy
rain. Wind gusts up to 30 mph are expected by mid to late
afternoon, with higher gusts of 35 to 45 mph occurring with any
outflow boundaries. Higher gusts up to 55 mph will not be out
of the question. The smoky/hazy conditions should begin to
improve from southwest to northeast due to the change in the
upper level flow pattern, as well as an increase in
moisture/clouds and mixing of the atmosphere from the showers
and storms. The exception looks to be Johnson County, which
will see an increase in the smoke as it gets pushed into this
area through the afternoon.
Conditions look to remain mostly dry Monday, as the ridge
reestablishes itself over the WY/ID border. Temperatures will be in
the upper 70s to upper 80s again, with drier air returning. This
will lead to elevated fire weather conditions across much of the
CWA. Wind gusts of 20 to 25 mph will occur by mid to late afternoon
for most locations. Any precipitation looks to be very isolated over
far southern portions of Sweetwater and Natrona counties.
Chances for precipitation do not look to be as widespread as
previously thought for Tuesday. A shortwave trough is still progged
to move over the Cowboy State, with diffluent flow occurring over
northwestern portions. Precipitation chances look to be in this
area, as well as Natrona/Johnson counties as the trough moves over
eastern WY. The upper level low will be stationary over the
PACNW Wednesday, allowing for additional shortwaves to move
through a southwest flow pattern aloft over the CWA. Isolated to
scattered showers and thunderstorms will remain possible, but
no signal for a widespread precipitation event. Similar
conditions look to return for Thursday, as the low begins to dig
southward over northern CA. This could lead to more widespread
precipitation, as the channel just around the low provides
better upper level diffluence. Precipitation chances are looking
good for western portions Friday, as the eastern periphery of
the upper low moves over this area. Temperatures will remain
largely unchanged during this time, with highs in the middle 70s
west of the Divide and middle to upper 80s east of the Divide.
Fire weather conditions will remain elevated, with attention
turning to Wednesday and Thursday as a result of the southwest
winds.
&&
.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 1136 AM MDT Sun Sep 7 2025
Smoke lingers across some terminals however visibility is expected
to remain >6SM, so have left smoke mentions out of the TAFs. A
shortwave moves across the state today, which will bring chances for
afternoon showers and thunderstorms to most terminals. BKN to OVC
high clouds this morning associated with the aforementioned shortwave
will continue to push northeast through the early afternoon. With
clearing behind that wave of high clouds, convective initiation is
expected by 19Z to 21Z west of the Divide and between 21Z and 00Z
east of the Divide. PROB30 and VCSH groups have been chosen
strategically to show confidence and most likely timing of potential
rain shower and thunderstorm impacts through the evening. Gusty
outflow winds around 25 to 35kts are expected to be the main threat
with the showers and thunderstorms through the evening. Note that a
few TEMPO groups have been included to cover most likely timing of
outflows in the evening from storms that are well away from the
terminals. Convective activity is expected to wane after 04Z to 06Z
with mostly light winds (less than 10kts) overnight through Monday
morning.
Please see the Aviation Weather Center and/or CWSU ZDV and ZLC for
the latest information on smoke, icing, and turbulence
forecasts.
&&
.RIW WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
UPDATE...CNJ
DISCUSSION...LaVoie
AVIATION...Hensley

NWS RIW Office Area Forecast Discussion