Latest ZFP from WFO RIW

		
National Weather Service Local Forecast for Star Valley Ranch
Updated: Thu Feb 06  1:17 pm MT

This Afternoon... Scattered snow showers after 3pm.  Cloudy,
with a high near 30. South southeast wind around 6 mph.  Chance of
precipitation is 40%. Total daytime snow accumulation of less than a
half inch possible. 

Tonight... Snow showers before 3am, then rain and snow showers.
 Temperature falling to near 27 by 8pm, then rising to around 32
during the remainder of the night. South southeast wind 6 to 14 mph,
with gusts as high as 20 mph.  Chance of precipitation is 80%. New
snow accumulation of 1 to 2 inches possible. 

Friday... Rain and snow showers, becoming all snow after 11am. 
Areas of blowing snow after noon. High near 33. Windy, with a south
southeast wind 14 to 19 mph becoming west 21 to 26 mph in the
afternoon. Winds could gust as high as 40 mph.  Chance of
precipitation is 90%. New snow accumulation of 1 to 2 inches possible.


Friday Night... Scattered snow showers, mainly before 11pm. 
Mostly cloudy, with a low around 15. North northwest wind 8 to 14 mph
becoming south southeast after midnight. Winds could gust as high as
20 mph.  Chance of precipitation is 50%. New snow accumulation of less
than one inch possible. 

Saturday... A 40 percent chance of snow showers.  Mostly
cloudy, with a high near 22. West wind around 7 mph.  Little or no
snow accumulation expected. 

Saturday Night... Mostly cloudy, with a low around 4. Light and
variable wind. 

Sunday... A 40 percent chance of snow showers.  Mostly cloudy,
with a high near 22. Calm wind becoming west around 5 mph in the
afternoon. 

Sunday Night... Partly cloudy, with a low around 0.

Monday... A 30 percent chance of snow showers after 11am. 
Partly sunny, with a high near 22.

Monday Night... A 20 percent chance of snow showers before
11pm.  Mostly cloudy, with a low around 4.

Tuesday... A chance of snow showers.  Mostly cloudy, with a
high near 16.

Tuesday Night... A chance of snow showers.  Mostly cloudy, with
a low around -4.

Wednesday... A chance of snow showers.  Partly sunny, with a
high near 15.

		

Latest AFD from WFO RIW

		
129 
FXUS65 KRIW 061915
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
1215 PM MST Thu Feb 6 2025

.KEY MESSAGES...

- Weather system impacts the area Thursday night through
  Saturday morning. Widespread snow and snow/rain chances 
  Friday.

- Gusty winds Friday, strongest across southern Wyoming.

- Colder temperatures Saturday behind the cold front.

&&

.DISCUSSION...
Issued at 1215 PM MST Thu Feb 6 2025

Not much to note for the remainder of today. Lesser winds will keep 
temperatures on the lower side compared to yesterday. Highs do still 
have quite the range though, ranging from the low 40s for southern 
areas to low 20s across the north. Attention is focused on the next 
weather system moving into western Wyoming tonight.

Snow chances will begin to increase across the western mountains for 
the latter half of this afternoon, with the main push coming in 
after 5pm. Zonal flow aloft will keep ample moisture (PWATs up to 
175% of normal) advecting into the area. The western mountains 
(focused on the Tetons, southern Absarokas, Wyoming/Salts, and Wind 
River Ranges) are the primary moisture receivers of this storm, but 
enough moisture will be around that all locations will have a 
chances to see precipitation through Friday. Downsloping will likely 
keep precipitation totals less for central basins (Bighorn/Wind 
River).

Friday is a bit of a mess. The first factor is precipitation type. 
By the afternoon, warmer temperatures across southern portions of 
the area will allow rain/snow (and even primarily rain) mixes to 
occur. It is difficult to know exactly where this will occur, but 
current models and trends have this line roughly from Cokeville in 
Lincoln County northeast to about Kaycee in Johnson County. South of 
this line will be the most likely areas to see rain or rain/snow 
mixes. Green River and Wind River Basins may also see this rain/snow 
mix occur as far north as Pinedale and Crowheart, respectively. 
Modeled snow levels keep South Pass in snow, so these rain chances 
are primarily for the lower elevations. As the cold front moves 
southward through the area Friday afternoon, additional chances of 
snow/rain showers occur. This will likely be the best chance for 
precipitation for the Bighorn and Wind River Basins as downsloping 
limits chances the rest of the day.

Though snow will linger past sunrise Saturday, a majority of 
precipitation will have fallen by then. Snow totals over the western 
mountains range from 1 to 2 feet where current Winter Storm Warnings 
are, with totals 6 to 12 inches for Yellowstone and the Absarokas 
where Winter Weather Advisories are. The Bondurant area is around 8 
inches, dropping to about 3 inches near Pinedale, so a Winter 
Weather Advisory is there too. Outside these highlights, lower 
elevations are generally less than an inch. The exception is the 
western valleys (Jackson and Star Valley) where 3 to 8 inches may 
fall. However, with warmer afternoon temperatures, actual 
accumulations may be more limited. Given the amounts, plus the winds 
Friday, have hoisted a Winter Weather Advisory for these valleys as 
well.

The other element to this storm is wind. Winds will begin to 
increase across western Wyoming and the Wind Corridor (roughly South 
Pass to Casper) around sunrise Friday. Southwest winds will be 
strongest ahead of the frontal passage mid-afternoon across southern 
Wyoming. Widespread gusts 30 to 55 mph occur from southern Lincoln 
County eastwards to the Casper area. There is about a 30% chance for 
winds of 55 mph or more for southern Lincoln County into the 
southern Green River Basin. Western Wyoming will also be windy, with 
gusts 25 to 35 mph for lower elevations. Winds decrease a little 
after frontal passage in the afternoon, but will still be gusty 
until Friday night.

There is some concern for blowing snow. However, with the strongest 
winds across southern Wyoming, this will coincide with the rain/snow 
mix, and therefore will limit the blowing snow threat. This could 
still occur though, especially Friday evening when rain/snow mix may 
become more snow than rain. Western mountain passes, however, will 
be impacted (blowing snow, limited visibilities) by periods of 
moderate to heavy snow and gusty winds.

Much cooler temperatures follow for Saturday, continuing into next 
week. Long range models are showing multiple systems move through 
next week, so continued precipitation chances.

&&

.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...
Issued at 1128 AM MST Thu Feb 6 2025

West of the Divide...KBPI/KJAC/KPNA/KRKS Terminals.

The next winter storm is quickly approaching western Wyoming. This 
will bring snow and rain impacts beginning after 00Z this evening. 
MVFR conditions are likely at KBPI, KPNA, and KJAC after 02-03Z. IFR 
conditions are most likely to prevail at KJAC tonight, with lower 
confidence at KBPI and KPNA. The bulk of the storm will be after 
sunrise Friday, and accordingly MVFR to IFR conditions will continue 
through the end of the period. This will also be a windy storm with 
gusts of 20 to 30 knots at KJAC/BPI/KPNA after around 13Z. KRKS will 
be the outlier and remain VFR, with a gusty southwest wind picking 
up toward the end of the period.

East of the Divide...KCOD/KCPR/KLND/KRIW/KWRL Terminals.

Terminals east of the Divide will not be as widely impacted from the 
incoming storm. Confidence is highest at KCOD for prevailing MVFR 
impacts, and potentially for visibility dropping to IFR there after 
12Z Friday. Showers will also be observed in the KCPR vicinity this 
evening, though lower confidence on terminal impacts precludes 
any prevailing impacts at this time. KLND may also see showers 
in the vicinity after sunrise Friday. Otherwise, wind will pick 
up at KCPR near the end of the period.

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...
Winter Weather Advisory from 11 PM this evening to 11 PM MST 
Friday for WYZ001-002-013-023-025.

Winter Storm Warning from 11 PM this evening to 11 PM MST 
Friday for WYZ012-014-015-024.

&&

$$

DISCUSSION...Wittmann
AVIATION...Myers