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Latest ZFP from WFO RIW

National Weather Service Local Forecast for Star Valley Ranch
Updated: Tue Jan 31  2:12 pm MT

This Afternoon... Mostly sunny, with a high near 13. Wind chill
values as low as zero. Southeast wind around 7 mph. 

Tonight... Patchy fog after 11pm.  Otherwise, mostly cloudy,
with a low around 3. Wind chill values as low as -10. East southeast
wind around 7 mph. 

Wednesday... Patchy fog before 11am.  Otherwise, mostly sunny,
with a high near 24. Wind chill values as low as -10. Southeast wind 6
to 8 mph becoming south southwest in the afternoon. 

Wednesday Night... Partly cloudy, with a low around 9. Wind
chill values as low as zero. Southeast wind around 6 mph. 

Thursday... Sunny, with a high near 32. Southeast wind around 6
mph becoming southwest in the afternoon. 

Thursday Night... Partly cloudy, with a low around 13.
Southeast wind around 6 mph. 

Friday... A 20 percent chance of snow showers after 11am. 
Mostly cloudy, with a high near 34. Southeast wind 6 to 8 mph becoming
southwest in the afternoon. 

Friday Night... A 20 percent chance of snow showers.  Mostly
cloudy, with a low around 18.

Saturday... A 20 percent chance of snow showers before 11am. 
Mostly cloudy, with a high near 31.

Saturday Night... Mostly cloudy, with a low around 17.

Sunday... A chance of snow showers.  Mostly cloudy, with a high
near 33.

Sunday Night... Snow showers likely.  Cloudy, with a low around

Monday... A chance of snow showers.  Mostly cloudy, with a high
near 28.


Latest AFD from WFO RIW

FXUS65 KRIW 312034

Area Forecast Discussion
National Weather Service Riverton WY
134 PM MST Tue Jan 31 2023

.SHORT TERM...(This evening through Wednesday night)
Issued at 1228 PM MST Tue Jan 31 2023

Temperatures remain well below zero in the lower Wind River Basin 
and Green River Basin this afternoon, thanks to high pressure, deep 
snowpack, and light winds. Other areas across the CWA have warmed up 
considerably from the record cold of previous days. Gusty west winds 
are helping to drive out the cold air in locations such as Casper, 
the Cody Foothills, Sweetwater County, and the upper Wind River 
Basin. Have kept with an SPS for the entire region to continue to 
drive home messaging about the bitter cold and cold wind chills. 
Though we are warming up in many areas, temperatures remain near 
zero, and in locations where winds are gusty, wind chill 
temperatures continue to be -15 to -20F. Not anticipating the need 
for any additional highlights for the wind chills, due to the 
warming actual air temps. 

A weak upper-level wave (if you can even call it that) will be 
passing through this evening through the overnight. Some light snow 
flurries are possible across the west, but no accumulations are 
expected. This wave will, however, increase cloud cover for most of 
the region tonight, and will also help to keep those gusty winds 
going, which will keep temperatures from falling much overnight. The 
central basins, where winds remain calm or very light, will likely 
see temps drop a bit, but temperatures are not expected to come 
close to the record lows of the last few nights, thanks to this 
cloud cover. 

The quiet conditions and warming trend continue into Wednesday. With 
WAA aloft, and snowpack and cool air at the surface, do expect some 
areas of patchy fog to develop in the favored areas where winds 
remain light. Favored areas include the Wind River Basin, western 
valleys, and the Green River Basin. The other location that could 
see patchy fog would be Worland and other low-lying areas in the 
eastern and central Bighorn Basin, as winds should remain light. The 
upper- to mid-level cloud cover will likely inhibit fog development 
tonight, but certainly more favored Wednesday night with skies 
clearing again through the day. 

One last note in the near-term forecast is the gusty winds. Gusts of 
35 to 45 mph have been common around Casper and Rock Springs today. 
These will decrease slightly overnight, but winds will generally 
remain on the gusty side in these west wind favored areas. The Cody 
Foothills are another area of concern for winds, as models do hint 
at a weak mountain wave signature. Winds have been mostly light so 
far today, but could see occasional strong gusts through tomorrow 
around Cody and especially towards Clark. Blowing snow, reducing 
visibility and causing travel difficulties is expected in the areas 
where winds are gusting 25 mph or greater. 

.LONG TERM...(Thursday through Tuesday)
Issued at 1228 PM MST Tue Jan 31 2023

Northwest flow aloft with a ridge moving onto the west coast. This 
will help with pushing out much of the cold air across the region, 
except for the central basins where it will remain basically 
trapped. The ridge axis will enter Wyoming Friday morning and 
continue steadily moving eastward. The good news is the 
temperatures will rebound nicely for the end of the work week into
the weekend. Wind River and Green River basins will most likely 
stay on the cold side, with the heavy snowpack and no wind to 
clear out the cold air. 

Friday evening will see a trough push into the northwestern parts of 
the forecast area for some snow chances through Saturday afternoon. 
Likely just flurries and not much accumulation with this trough. 
There will then be another weak, quick moving ridge to dry us out, 
and then a new trough will move onshore and push into the forecast 
area Sunday. Models are currently indicating snow showers across the 
west by midday Sunday, and then chances spreading east of the divide 
late Sunday into Monday morning. For now it looks like most of the 
accumulations will be across the west and the Bighorn Mountains. 
Central areas won't see be much in the way of accumulations. This 
trough will push through the area and be replaced by northwest flow 
once again as another ridge moves into the western U.S. 

The wind speeds will be a bit of a challenge for the end of the week 
and weekend with the potential to blow around that pesky snow. 
Speeds are going to be on the increase late Thursday evening into 
Friday for Natrona County, eastern Sweetwater and southern Johnson 
counties, as well as the central mountain ranges. Southwest winds 25 
to 35 mph with gusts possible to 45 mph in those areas. Saturday and 
Sunday will see the gustiness as well, though a little weaker. 


.AVIATION...(For the 18Z TAFS through 18Z Wednesday afternoon)
Issued at 1033 AM MST Tue Jan 31 2023

A weak upper-level wave will pass over the region this evening and 
overnight. This will result in mostly BKN to OVC skies and some 
occasional very light snow showers. Best chances for snow showers 
are at KJAC terminal. MVFR conditions are possible in these snow 
showers, but otherwise VFR conditions are expected to prevail 
through the next 24 hours at all terminals. Gusty winds also remain 
possible at KCOD, KCPR, and KRKS. KCPR will see the strongest winds 
with frequent gusts to 35 to 40kts expected through 00Z. Mountain 
wave influences are possible at KCOD and thus have included LLWS in 
the TAF through 00Z. Patchy fog is possible at KBPI, KJAC, KPNA, and 
KRIW terminals Wednesday morning, but have opted to not include fog 
in TAFs due to low confidence in fog development. 

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


Issued AT 1228 PM MST Tue Jan 31 2023

High pressure will bring a warming trend and relatively quiet 
weather to the region through the rest of the week. The Wind River 
Basin and Green River Basin will remain colder than normal due to a 
strong surface temperature inversion and calm or very light winds. 
Gusty west winds with gusts 25 to 40 mph are impacting favored areas 
across the south, near Casper, and along the Cody Foothills, and 
will continue through Wednesday. A brief light snow flurry is 
possible tonight, but no accumulations are expected. Next chances 
for snow will be Friday and Saturday for the western mountains, and 
Sunday for the rest of the region.





SHORT TERM...Hensley
LONG TERM...Swanson


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