Farlow Trail, Wyoming Weather Forecast Discussion

652
FXUS65 KRIW 160340
AFDRIW
Area Forecast Discussion
National Weather Service Riverton WY
940 PM MDT Mon Sep 15 2025
.KEY MESSAGES...
- Shower and thunderstorm chances (40-60%) exist across the Wind
  Corridor and far northwest Wyoming beginning Tuesday morning.
  Chances spread mainly along and east of the Divide Tuesday
  afternoon.
- Cooler air brings the potential for frost in western valleys
  and basins tonight. Freeze Warnings are in effect. These
  temperatures are again likely the next few nights.
- Daily shower and thunderstorm chances again on Wednesday.
  Drier and warmer air moves in late this week.
&&
.UPDATE...
Issued at 1221 PM MDT Mon Sep 15 2025
The main consideration for this update is freezing temperature (32F
or less) potential tonight across western valleys and basins. Models
are in good agreement with a dry slot moving into the area as the
upper low moves over Wyoming tonight. If that happens, the drier air
should limit clouds across central areas, including Star Valley,
Jackson Valley, and the Green River Basin. Therefore, confidence is
fairly high (70%) that widespread temperatures of 32 degrees or
lower will occur. This is very dependent on cloud cover decreasing,
however. Freeze Warnings have been issued to cover the likelihood of
frost formation. Cold prone locations, like along rivers and near
Bondurant will see the coldest lows, potentially in the mid-20s.
As the aforementioned low moves over Wyoming tonight, the drier air
should limit precipitation chances across central areas, with
chances continuing across portions of northern and southern Wyoming
through Tuesday. Central areas could see better storm chances pick
up Tuesday afternoon as moisture fills in. Snow levels could be as
low as about 9000ft at times through Tuesday.
&&
.DISCUSSION...
Issued at 200 AM MDT Mon Sep 15 2025
The next trough is moving into western WY as I type this, with
showers and thunderstorms on the increase. These showers and
thunderstorms will continue to spread to the northeast
generally across the northern half of the state through this
afternoon. Midlevel support will peak during the mid afternoon,
which, along with dry air near the sfc, will lead to some gusty
winds from stronger storms this afternoon, mainly across central
WY. The midlevel trough stalls around northern WY tonight,
leading to continued showers and thunderstorms for northern WY.
This will also bring a band of showers across southern WY
increasing after midnight tonight. The trough continues to spin
across the state on Tuesday, leading to another round of showers
and thunderstorms for most of western and central WY. As the
trough slowly drifts to the east Wednesday morning, rain
chances will finally start to decrease, with central WY being
the final area to see an end to precip. While most of western WY
is settling into total accumulations of 0.10" to 0.25", Johnson
and Natrona Counties are seeing an increasing probability of
0.50" (currently near 40% chance).
The cold pool associated with this wave will also bring some
cooler temperatures overnight tonight and Tuesday night, mainly
for lower elevations west of the Divide. Probabilities of
temperatures below freezing remain modest (20-30%), the most
likely locations would be the upper Green River Basin (Hoback
to Bondurant), and across most of Yellowstone NP.
The latter half of the week will be a return to more stable
conditions. Models are differing on the final wave rotating
around the main trough moving east. If this wave stays far
enough west, then Thursday may see one more day of showers for
the I-25 corridor. Once this is through, a more stable regime
sets up, with warmer temps and minimal rain chances.
&&
.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 932 PM MDT Mon Sep 15 2025
Skies are expected to gradually clear overnight. There remains a 20%-
30% chance of fog development along the Jackson Hole Valley (KJAC).
Confidence is not high enough to include vsby/cig reductions at KJAC
but the potential is reflected as a FEW002 cloud group beginning
at 10Z Tuesday morning. If fog develops, there is a 30% chance
it could linger through at least 17Z Tuesday. There is a 15%-20%
chance of low VFR to MVFR clouds developing at KCOD, KRIW, and
KLND after 10Z/12Z Tuesday morning. This lower cloud development
is reflected in a FEW020 or FEW040 cloud group.
Rain showers are forecast to develop across southern Wyoming
around 10Z at KRKS and push into KCPR by 14Z. Showers are
forecast to prevail for a few hours at both KRKS and KCPR.
Scattered low clouds around FL015 are possible at KCPR with
these showers and this potential is reflected by a FEW015 cloud
group. Scattered showers and thunderstorms are forecast to
develop along and east of the Divide after 21Z Tuesday with
PROB30 groups covering most likely timing. Conditions are
expected to stay VFR with any showers and thunderstorms;
however, a brief period of reduced flight conditions cannot be
ruled out in a heavy shower or thunderstorm.
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...
Freeze Warning from 1 AM to 7 AM MDT Tuesday for WYZ013-023-
025-026.
&&
$$
UPDATE...Wittmann
DISCUSSION...Straub
AVIATION...Gerhardt/Hensley

NWS RIW Office Area Forecast Discussion