National Weather Service Local Forecast for Star Valley Ranch
Updated: Mon Jun 23  2:30 pm MT

This Afternoon... Sunny, with a high near 69. West northwest
wind 5 to 8 mph. 

Tonight... Increasing clouds, with a low around 40. West
northwest wind 5 to 9 mph becoming light and variable. 

Tuesday... Isolated showers and thunderstorms after 2pm. 
Mostly sunny, with a high near 75. Light and variable wind becoming
northwest 5 to 10 mph in the afternoon.  Chance of precipitation is
20%.

Tuesday Night... Mostly clear, with a low around 41. North
northwest wind 5 to 10 mph becoming light and variable  after
midnight. 

Wednesday... Sunny, with a high near 78. Calm wind becoming
west around 6 mph in the afternoon. 

Wednesday Night... Mostly clear, with a low around 46. West
wind around 6 mph becoming light and variable. 

Thursday... Sunny, with a high near 82. Southeast wind 5 to 8
mph becoming west southwest in the afternoon. 

Thursday Night... Partly cloudy, with a low around 49.

Friday... Sunny, with a high near 83.

Friday Night... Mostly clear, with a low around 50.

Saturday... Sunny, with a high near 82.

Saturday Night... Mostly clear, with a low around 48.

Sunday... Sunny, with a high near 85.

	

	
208 
FXUS65 KRIW 231831
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
1231 PM MDT Mon Jun 23 2025

.KEY MESSAGES...

- Dry and warmer day today with isolated showers and storms 
  around Johnson County and the Absaroka Mountains.

- Strong to severe thunderstorms possible Tuesday, especially
  around Johnson and Natrona Counties.

- Warmer Thursday into the weekend, with isolated afternoon
  thunderstorm chances.

&&

.UPDATE...
Issued at 1229 PM MDT Mon Jun 23 2025

No major changes to the forecast from the morning discussion below. 
There were some low temperature records set this morning for 
locations east of the Divide, with many western basin/valley 
location lows under 32 degrees. The focus remains on the severe 
potential tomorrow (Tuesday). The 12z hi-res models have convection 
across eastern portions of the area starting about 1pm, with the 
HRRR having the last storm exiting to the east around 4am Wednesday. 
The best ingredients continue to be over Johnson/Natrona
Counties. 

&&

.DISCUSSION...
Issued at 306 AM MDT Mon Jun 23 2025

Welcome to the start of the first work week of summer. It does not 
feel like it though. I duck outside a short time ago and it was 
chilly, with temperatures in the 40s at the office. Other locations 
are even cooler though. Both Big Piney and Pinedale are at or 
below freezing with other locations in the 30s. With this, we 
will leave the freeze warnings in effect through the expiration 
time at 8 am, although temperatures will warm before that since 
sunrise is before 6 am. Other then that, there are few concerns 
today. Most locations will have a nice day that will feel more 
like May than late June with high temperatures averaging 10 
degrees below normal. As for convection, most locations will 
have upper level convergence today and with the lack of 
moisture, most places will be rain free. The main exception may 
be portions of Natrona and Johnson County where a thin area of 
CAPE and negative lifted indices may be enough for an isolated 
late day or evening shower or storms, but the chance is less 
than 1 in 5. We can't rule one out in the Absarokas as well, but
with the chance less than 1 out of 10, we will keep the 
forecast dry for now. 

By far the most interesting and impactful day of the forecast would 
likely be Tuesday, especially late in the day and in the evening. We 
have a decent set up for some severe weather. A trough will be 
approaching the area in the afternoon, increasing upper level 
divergence. We also have a jet over us, although there are some 
model differences in where exactly the left front / right rear 
couplet will set up. We will also have a pseudo dryline setting up 
near the Continental Divide, which may be the line for development. 
Soundings also show fairly steep mid level lapse rates and veering 
winds with a decent amount of directional and speed shear. As for 
stability parameters, it depends on the model. Some show as much as 
1500 J/Kg of CAPE with lifted indices as low as minus 5, others are 
not as impressive. There are some limiting factors though. The main 
one being moisture. Surface dew points are only expected to be 
in the 40s, and I would like to see 50s for a good outbreak of 
severe weather. However, the potential is there. With the decent
shear and potential for rotating updrafts and tilted storms, 
the main threat would be large hail, with areas east of 
Interstate 25 from north of Casper through eastern Johnson 
County in a hatched area for hail. We do not see this much in 
this part of the country. And many places could see strong wind 
gusts, but this is the case with any thunderstorm in Wyoming. 
And yes, we do have the potential for a tornado. It appears 
small right now, since Lifted Condensation Levels look fairly 
high, which could keep any rotation from touching down. There is
a 2 percent area across eastern portions of the area though. As
for where, the best chance would be along and east of the 
Bighorns, where low level upslope flow would aid in convective 
initiation, but most areas across the northern half of the state
could see one. Soundings are also showing a decent cap, so this
may turn out to be a later show, starting later in the 
afternoon and continuing into the evening and possibly after 
midnight. Severe weather is not a certainty, but there is a 
decent chance, especially in Johnson and Natrona Counties later 
Tuesday afternoon and Tuesday evening. 

Thunderstorms will remain possible on Wednesday as another 
shortwave moves across the area, but coverage would be more limited. 
We will again have a pseudo dryline across the area, but likely 
further north. There will be more moisture in far northern and 
eastern areas though, which may enhance the threat of heavy rain. 
Hard to give details on specific threats on this day, but the 
potential is there for another active day, though possibly in a 
smaller area.

Starting on Thursday and continuing into the weekend, we will move 
into a more summer like pattern with warm temperatures, generally 
above normal but not record breaking. A couple of shortwaves will 
pass by to the north and may bring isolated convection each 
afternoon across northern Wyoming. But on these days, most areas 
will remain rain free each day. If there is a more active day, most 
guidance favors Saturday, but shortwaves are hard to time this far 
out.

&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 1107 AM MDT Mon Jun 23 2025

VFR conditions across all terminals throughout the TAF period. Winds 
remain light throughout much of the period with a slight increase 
expected for Tuesday as a result of a nearing disturbance. Skies 
remain mostly clear with high level cirrus starting to develop 
throughout the day Monday. Clouds will increase by the end of the 
period as chances for showers and thunderstorms develop on Tuesday.

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...Wittmann
DISCUSSION...Hattings
AVIATION...Dziewaltowski

	

	
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