Grand Targhee

000
FXUS65 KRIW 261050
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
450 AM MDT Mon Oct 26 2026

.KEY MESSAGES...

- Any showers ending early, then a somewhat warmer and mainly
  dry day today with more sunshine.

- An approaching weather system will bring a period of snow to
  western Wyoming tonight, and strong to potentially high wind
  East of the Divide on Tuesday.

- Another fast moving system may bring some snow to southwestern
  Wyoming later Tuesday night.

- Mainly dry and somewhat warmer from Wednesday through most of
  Friday.

&&

.DISCUSSION...
Issued at 232 AM MDT Mon Oct 26 2026

I have to apologize for the forecast yesterday, the rain showers 
reached a bit further north than I or most of the guidance thought. 
However, most areas need rain so complaints were few. And, many 
areas will an additional couple of chances of precipitation over 
the next week or so.

We still have a few light showers out there early this morning, but 
these should be gone by sunrise, which is getting rather late (after 
7:30 am). All in all, today looks like a fairly low impact day as 
shortwave ridging should bring a mainly dry and somewhat warmer day 
to the area. We have a couple of small concerns. The first is that 
maybe the fog monster could come crawling out of his lair and bring 
some reduced visibility. He is still sleeping at this time but we 
will see if he wakes up. The other will be some gusty wind 
developing in the favored Muddy Gap to Casper area, but nothing 
unusual through around midnight. There should be more sun today as 
well, and this should allow for temperatures to be a bit warmer than 
over the weekend.

The first weather maker, an area of low pressure now moving onshore 
in the Pacific Northwest, will be the first concern of the forecast. 
Concerns remain the same as yesterday, with a period of snow, 
potentially heavy in western Wyoming, and potential strong to high 
wind in areas East of the Divide. We will start with the snow. Snow 
should hold off until after sunset this evening. We also have decent 
model agreement in having the heaviest precipitation between 9 pm 
and 3 am tonight, when the trough axis and cold front move through 
the area. Snow levels will start fairly high, above 8500 feet, as 
700 millibar temperatures are expected to be at 0 celsius or above. 
These will quickly drop to around minus 4 to minus 6, dropping snow 
levels to the valley floors. There will also be an approaching 100 
knot jet streak, enhancing lift. The limiting factor will be speed 
of the system, as the heaviest precipitation should only last at 
most six hours, possibly as few as three. This should limit amounts 
somewhat. Most areas should see at least a coating in the west. 
However, the area that has a greater than 1 out of 2 chance of 3 
inches or more is largely restricted to areas above 9500 feet. As 
for areas with advisory level amounts (6 inches in the mountains), 
this is largely restricted to areas above 10500 feet and in places 
like southwestern Yellowstone Park, where impacts would be minimal. 
So, we will not issue advisories at this time. However, there could 
be a period of a few hours later this evening when there could be a 
period of heavy snow and gusty wind that could make travel 
difficult, especially over the mountain passes. The steadiest snow 
should end by sunrise, with only a few leftover showers after 
sunrise Tuesday.

The other concern is strong to potentially high wind. It will be a 
decent setup for strong wind with an 100 to 110 knot jet streak 
moving across the area and a trough to help mix strong wind to the 
surface. There is also a decent area of 50 to 55 knot wind at 700 
millibar wind in the favored southwest flow areas, mainly from Muddy 
Gap through Natrona County, with the strongest wind between 6 am and 
noon on Tuesday. Probabilistic guidance is still borderline though. 
There is a 1 in 2 chance of wind gusts past 55 mph in portions of 
the area. However, much of this area is over areas that have higher 
thresholds (65 mph for East Casper, 75 mph for the higher 
elevations). So, we will continue the watch for now and let the day 
crew take one more look at it. Wind should decrease late Tuesday 
into Tuesday night as the low moves away and the pressure gradient 
decreases.

There is one more concern for Tuesday night, especially late in the 
form of a trailing shortwave that would mainly impact southwestern 
Wyoming. There is not a ton of moisture with it. However, there will 
be some right rear quadrant jet energy to produce more lift. The 
current forecast may be too dry. This will be another quick system 
which should limit amounts but the potential for an inch or two of 
snow in places like Kemmerer, Farson, Pinedale or even Rock Springs 
later Tuesday night. Again, with the fast movement of the system, 
all precipitation should end by sunrise Wednesday.

Flat ridging should then bring mainly dry weather Wednesday through 
most of Friday. My gut feeling is that the forecast for Friday looks 
to wet. The next system in the form of a low moving in from the 
southwest will bring the next chance of showers for next weekend. 
There are still differences in the details, with some models showing 
a deep trough developing across the western United States and others 
showing the trough flatter and further north. So, details are still 
difficult to hash out at this time. Southwest should bring near to 
somewhat above normal temperatures through the end of the workweek 
and possibly to Saturday as well.

&&

.AVIATION /12Z TAFS THROUGH 12Z TUESDAY/...
Issued at 443 AM MDT Mon Oct 26 2026

Areas of low clouds will persist into the morning for portions
of the area, with the highest likelihood in vicinity of KCPR,
KBPI, KPNA and KRIW. At KRIW, areas of fog have formed and will
be around from time to time through around 16Z with periods of
IFR to LIFR conditions before it gradually burns off. Largely
VFR conditions are then expected at all TAF sites from around
16Z Monday through 04Z Tuesday. Wind should remain under 11
knots at all terminals through 06Z tonight, with the exception
of KCPR which will see a gusty wind develop this afternoon and
persist through the night, with gusts over 30 knots likely (70
percent chance) after 08Z Tuesday.

A weather system will move into western Wyoming after 04Z
tonight and bring a period of snow and rain changing to snow.
The rain and snow will mainly impact KJAC, KPNA and KBPI between
05Z and 12Z, with the highest chance of IFR conditions (around 
50 percent) in vicinity of KJAC. Mountain obscurations are 
expected during the time of this period of rain and snow.

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

.RIW WATCHES/WARNINGS/ADVISORIES...
High Wind Watch from late tonight through Tuesday afternoon 
for WYZ019-020.

&&

$$

DISCUSSION...Hattings
AVIATION...Hattings