FXUS65 KRIW 100347

AFDRIW



Area Forecast Discussion

National Weather Service Riverton WY

947 PM MDT Fri May 9 2025



.KEY MESSAGES...



- Any storm activity has diminished and pushed east and 

  southeast of the Casper/Casper Mountain area out of Natrona 

  County. Quiet overnight to come.



- Warm temperatures over the weekend that will lead to elevated

  water levels due to snowmelt. 



- Increasing storm chances come Sunday afternoon along with

  elevated fire weather conditions into Monday as well. 



- The next system and best chance for a more widespread

  precipitation event.



&&



.UPDATE...

Issued at 142 PM MDT Fri May 9 2025



Isolated convection will continue today, focused mainly on the 

eastern half of the area off of the higher terrain. This activity 

will drift to the southeast through the afternoon, ending around 

sunset. Gusty outflow winds to 35 mph or so will be the main 

concern. 



No big changes this afternoon to the upcoming forecast. The weekend 

will see temperatures warm to near 20 degrees above normal for most 

of the area. The ridge will begin to move east on Sunday, allowing 

for the return of more widespread convection chances, especially 

west of the Divide. 



There are a couple of resultant weather concerns we are beginning to 

key in on. One is the potential for rising rivers and streams given 

the multiple days of above normal temperatures expected this 

weekend. The other is fire weather conditions as southwesterly winds 

increase ahead of next week's system. This will first be a concern 

on Sunday, though Monday will be the day with the strongest wind and 

lowest humidity.



&&



.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 /06Z TAFS THROUGH 06Z SUNDAY/...

Issued at 946 PM MDT Fri May 9 2025



High pressure keeps VFR conditions in place over the next 24 hours. 

Breezy winds develop for some sites Saturday. Clouds begin to 

increase from the west near the end of the TAF period, ahead of the 

next weather system.



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.



&&



$$



UPDATE...Myers

DISCUSSION...Straub

AVIATION...Wittmann