FXUS65 KRIW 261848

AFDRIW



Area Forecast Discussion

National Weather Service Riverton WY

1248 PM MDT Thu Jun 26 2025



.KEY MESSAGES...



- A warm and pleasant day across the Cowboy State today with

  plenty of sunshine.



- Warm temperatures, low RH, and gusty winds have lead to a Red

  Flag Warning being issued for portions of Natrona County

  Friday afternoon through the evening.



- Elevated to near critical fire weather conditions are expected

  to be widespread Friday into Saturday.



- Small chances for daily showers and thunderstorms will be

  possible through the weekend with the highest likelihood being

  over northern WY.



&&



.UPDATE...

Issued at 1244 PM MDT Thu Jun 26 2025



The forecast continues to remain mostly unchanged with fire weather 

conditions becoming the next concern through the weekend. 

Temperatures will continue to gradually warm through the start of 

next week. Highs today will range from the mid to upper 70s west of 

the Divide and mid to upper 80s east of the Divide. Temperatures are 

expected to remain above normal through the rest of June with highs 

in the low 80s to low 90s. Through the start of next week a few weak 

shortwaves will move over the region, which will bring increased 

winds and slight chances for showers and thunderstorms. 

Precipitation chances overall remain low and will likely be fairly 

limited. Better chances for more widespread showers and 

thunderstorms do not look to arrive until next week. 



As mentioned earlier the main concern over the next few days will be 

fire weather conditions. A Fire Weather Watch for portions of 

Natrona County has been upgraded to a Red Flag Warning. This will go 

into effect Friday afternoon through Friday evening. While this is 

the only location with a fire related highlight, other areas are 

going to see elevated to near critical conditions Friday and 

Saturday. Winds will increase both Friday and Saturday with fairly 

widespread wind gusts of 20 to 30 mph. RH values will be bone dry 

across much of central and southern WY with values ranging from 10 

to 15%. These fire weather conditions look to improve slightly by 

Sunday with weaker but still breezy winds and moister RH values. 



Looking forward to the end of June and start of July, the CPC 

outlook is suggesting above normal temperatures prevailing over the 

region. Precipitation chances are slightly above normal as well, 

likely in the form of afternoon convective showers and 

thunderstorms. However, there are some signals that moisture may 

eventually be cut off to the region. This would lead to drier 

conditions and possibly a transition from the convective season to 

the heart of fire weather season.



&&



.DISCUSSION...

Issued at 249 AM MDT Thu Jun 26 2025



June is typically the most active month for severe weather 

(hail, tornadoes) etc in western and central Wyoming and the 

past month is no exception. Eventually, we begin to transition 

into a drier time when fire weather concerns become the main 

concern and while we are not completely there yet, we have 

begun the slow transition. 



Flat ridging will dominate the weather through around Saturday. This 

typically means flow will be mainly from the west and southwest, and 

will bring warmer temperatures. We will see a period of above normal 

temperature through the weekend. Areas in our warmer locations, like 

Greybull and Worland, will see highs climb back close to the 90s 

today with 80s widespread across most of the lower elevations. We 

could still see a few thunderstorms today, mainly across the 

northern mountains and adjacent foothills as a shortwave brushes by 

to the north. The atmosphere is much drier today though. This is the 

first day in a while that precipitable water values are below 

the 50th percentile. This means coverage will be isolated (at 

most a1 out of 5 chance). However, it also means dewpoint 

depressions will be large so any thunderstorm or shower that 

forms could have strong wind gusts of 40-50 mph. As for fire 

weather concerns, humidity will be low, falling below 15 percent

in many lower elevation locations (especially across central and

southern portions). Wind should remain on the light to moderate

side, so critical fire weather is not expected.



Concerns do increase on Friday though. Another shortwave will move 

by to the north. Again, isolated storms (a 1 out of 6 chance) 

will be possible in the northwest but this is the main concern.

The pressure gradient will be a bit tighter. In addition, a jet

streak moving across Montana will put Wyoming in the right 

front quadrant of the jet, enhancing downward momentum of 20 to 

30 knot 700 millibar winds. Increased southwest flow will also 

bring a hot day, with fairly widespread highs in the low to mid 

90s. Humidity will be very low as well, falling into the single

digits at this time. Additionally, fuels have turned critical 

in a few locations. One of these locations is Natrona County, 

and this is also one of our windier locations. With this, we 

have hoisted a Fire Weather Watch for Friday afternoon and 

evening. Other locations could have elevated to critical fire 

weather, but less wind or fuels not being critical should 

prevent more widespread watches.



On Saturday, we have a few more questions. We thought about going 

two days on the Watch, but have held off for now. For one, the 

best jet forcing moves a bit further north, reducing downward 

momentum. The result is wind should be a bit lighter. In 

addition, most guidance shows a bit more moisture moving in, 

raising dewpoints anywhere from 5 to 10 degrees, making things 

more borderline. The increased moisture and with what forcing we

have from the right rear quadrant of the jet, thunderstorm 

chances may increase a bit, but the chance is still only around 

1 out of 4. 



A somewhat stronger wave and associated weak cold front will swing 

through the area on Sunday, taking the edge off of the heat. It will 

also increase chances for showers and storms in eastern portions of 

the area, where surface easterly flow may provide convective 

initiation, mainly in Johnson and Natrona Counties. Ridging then

builds northward for early next week, resulting in above normal

temperatures again. Most convection these days should be in the

mountains and adjacent foothills, but any spot generally only 

has a 1 in 4 chance of a shower or thunderstorm. Another wave 

may bring increased showers and storms for Wednesday, but timing

this far out is uncertain.



&&



.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...

Issued at 1105 AM MDT Thu Jun 26 2025



VFR flight conditions prevail the entire TAF period at all terminals 

with afternoon CU development and increasing mid-level clouds. 

Westerly winds increase between 19-22Z at all west of the Divide 

terminals and KCPR with gusts around 20kts. Gusty winds diminish 

around sunset. Winds less than 10kts are forecast at all other 

terminals.



Isolated showers and thunderstorms are possible across western and 

northern Wyoming between 21Z-04Z. Confidence is highest (30%) in a 

shower and/or thunderstorm at KCOD and this is reflected as a PROB30 

group. Confidence is too low (20%) in a shower and/or thunderstorm 

at KJAC and KWRL so there is no mention is TAF at this time. A 

thunderstorm could produce gusty outflows around 30kts. 



Please see the Aviation Weather Center and/or CWSU ZDV and ZLC for 

the latest information on smoke, icing, and turbulence

forecasts.



&&



.FIRE WEATHER...

Issued at 1244 PM MDT Thu Jun 26 2025



Elevated to near critical fire weather conditions will be

prevalent across much of central and southern WY on Friday and 

Saturday. Temperatures are forecast toremain above normal into 

the weekend. Low RH will range from 10 to 20% across much of 

this area with winds gusting 20 to 30 mph at times. A Red Flag 

Warning has been issued for zone 280 as a result of these 

conditions and dried fuels.



&&



.RIW WATCHES/WARNINGS/ADVISORIES...

Red Flag Warning from noon to 9 PM MDT Friday for WYZ280.



&&



$$



UPDATE...Dziewaltowski

DISCUSSION...Hattings

AVIATION...Gerhardt

FIRE WEATHER...Dziewaltowski

