FXUS65 KRIW 191726

AFDRIW



Area Forecast Discussion

National Weather Service Riverton WY

1126 AM MDT Tue Aug 19 2025



.KEY MESSAGES...



- High pressure today brings well above normal temperatures and

  very dry conditions with relatively light winds. There is a

  small chance (10-15%) chance of showers and thunderstorms over

  the Bighorn mountains this afternoon. Smoke continues in the

  Bighorn Basin from area fires.



- Wednesday will see near record high temperatures as high

  pressure continues, with some locations east of the divide

  hitting 100 degrees. Northwest WY will have a slight chance

  (10-20%) chance of showers in the morning, with isolated

  showers and thunderstorms in the afternoon.



- A cool front early Thursday morning will bring more seasonable

  temperatures Thursday and Friday, with increasing chances of

  showers and thunderstorms. Far west-central WY though will

  remain very warm and dry with gusty west winds in the

  afternoon.



&&



.DISCUSSION...

Issued at 130 AM MDT Tue Aug 19 2025



WV imagery continues to show the southwest flow aloft across the

CWA as it continues to weaken and become more broad due to the

building higher heights centered near the Four Corner Region.

Mainly clear on IR with nothing on radar of consequence.



With increasing convergence aloft, the aforementioned ridge

continues to build in across the CWA giving way to hotter than

average temperatures and dry conditions Tuesday afternoon. Near

record temperatures for some parts east of the Divide but better

chances Wednesday afternoon with the strengthening high. Weak

winds and mainly clear skies continue much of these days. Some

weak chances (<15%) across northwest portions of the CWA to

include the Absarokas and Yellowstone for Wednesday afternoon

and early evening with a subtle mid level shortwave around the

aforementioned high. However, confidence low on anything

significant if anything at all at this time. The weak flow 

aloft will not see that strong of outflows but some lightning 

may be of concern with the ongoing fire weather threat currently

with active fires. 



Otherwise, expect a pattern change come Thursday as the high

weakens with decreasing convergence aloft retreating some to the

south allowing for monsoonal moisture to increase into the CWA

from the southwest. Isolated thunderstorms increase in the

afternoon and evening hours with the upper level trough 

skirting to the north of the CWA through Montana and southern 

Canada. Thunderstorm coverage increases Friday afternoon and 

even over the weekend, especially east of the Divide becoming 

more widely scattered. As always, frequent lightning and gusty 

outflows the main concern this time of year for fire weather. 

The aforementioned higher heights near the Four Corner Region 

looks to build back up early next week that will give way to a 

dryer and warmer than average end to the month of August.



&&



.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...

Issued at 1052 AM MDT Tue Aug 19 2025



VFR and SKC conditions will prevail through the TAF period. Smoke 

from the Red Canyon Wildfire in the southern Bighorn Basin may lead 

to reduced VIS at KWRL, down to MVFR is possible (20%). Wind will 

remain light, less than 10 knots, across the area today through 

Wednesday morning. No chance of rain for the next 24 hours.



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...

Air Quality Alert until 1 PM MDT Wednesday for WYZ003-008.



Air Quality Alert until 1 PM MDT Wednesday for WYZ004>007.



&&



$$



DISCUSSION...Lowe

AVIATION...Rowe