FXUS65 KRIW 091621

AFDRIW



Area Forecast Discussion

National Weather Service Riverton WY

1021 AM MDT Fri May 9 2025



.KEY MESSAGES...



- Another warm day across the state with highs in the 70s and

  low 80s.



- Isolated showers and thunderstorms will develop generally

  along and east of the Bighorn Mountains this afternoon. 



- Strong ridging continues into the weekend, with temperatures

  well into the 70s and 80s.



- Gusty winds, warm temperatures, and low humidity will bring

  elevated to critical fire weather conditions Sunday and Monday

  for much of the area.



- The ridge is broken down by a potent longwave trough late in

  the weekend into early next week, with increasing chances for

  rainfall.



&&



.DISCUSSION...

Issued at 211 AM MDT Fri May 9 2025



The H5 ridge continues to build, and will stretch northward

along the Rockies today. The ridge will continue to bring

temperatures will above normal in the 70s and low 80s this

afternoon. The weak shortwave that's drifting along the 

northern edge of the ridge will mosey across the Bighorn Range 

this afternoon, and will tap enough instability from heating of 

the day to spark a few showers and thunderstorms. Steer flow is

toward the southeast, so areas of Johnson and Natrona Counties 

also have a 20 to 30 percent chance for thunderstorms as well. 

As was that case assisted, once peak heating wanes and the 

ridge continues building northward, shower activity will fade 

away early in the evening.



The weekend will be marked by even warmer conditions as the axis

of the ridge centers on Wyoming. H7 temps still lead to highs 

in the mid to upper 70s west of the divide and low to mid 80s 

east of the divide. Early next week, the ridge gets pushed east

by a longwave trough off the PacNW coast. Western WY remains 

pinned between the two, but the H7 heat ridge holds across the 

state Monday and Tuesday. Temps will be a few degrees cooler 

these days, held down by the increasing cloud cover from the 

approaching trough. Models still having trouble resolving the 

progress of the trough, with GFS running faster, and EC holding 

back a bit, but feeding more Pacific moisture into the state. 

With either solution, there is an increasing potential for an 

extended period of rain/snow for western WY into midweek.



&&



.AVIATION /12Z TAFS THROUGH 12Z SATURDAY/...

Issued at 519 AM MDT Fri May 9 2025



Not much weather to impact aviation operations for the next 24 

hours. Conditions will remain VFR and mostly SKC. There will be a 

few isolated rain showers and thunderstorms that develop off the 

eastern Absaroka Mountains, eastern Bighorn Mountains, and Casper 

Mountain Friday afternoon. There is about a 20-30% chance that KCOD 

and KCPR will be impacted by one of these showers/storms. Even if 

they are conditions should remain VFR.



Wind will remain light across most of western and central Wyoming 

through the TAF period. The strongest wind will occur at KCOD Friday 

afternoon and KRKS Friday night (about 10 knots). 



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...

None.



&&



$$



DISCUSSION...Straub

AVIATION...Rowe