FXUS65 KRIW 151706
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
1106 AM MDT Thu Oct 15 2026

.KEY MESSAGES...

- Some lingering clouds into the afternoon but mostly sunny and
  remaining on the cool side. Breezy winds widespread, highest
  across Johnson County. 

- Clear and cold tonight, with lows in the 20s for all areas.
  Freeze Warnings have been issued for those are that have not
  already had a morning freeze.

- Dry and milder through the upcoming weekend with highs mainly
  in the 50s and 60s.

&&

.DISCUSSION...
Issued at 152 AM MDT Thu Oct 15 2026

The H5 trough continues to exit to the southeast, and is
gradually taking the clouds and precip with it. As of current
writing time, the only remaining light rain is confined to
Natrona County, and continues to draw to the southeast as well.
Most light rain should be complete by 6AM, but light sprinkles
may continue on Casper Mountain for a couple more hours. Skies
will clear through the rest of the day, and with good cold air
advection still in place, highs will struggle to reach the 50s.
This will be accompanied by a modest northerly breeze, making
for a brisk autumn day. Areas across Johnson County will hold
some more of the influence of the sfc low gradient, so winds
will be higher through the day, gusting 30 to 40 mph through the
afternoon. Watch for cross winds along the I-90 corridor. Winds
will die off quickly after sunset as high pressure sweeps in.
This sets the stage for the first freeze of the season for most
of the state. Most areas will fall into the 20s for several
hours tonight. The only inhibiting factor may be enough of a
breeze in the Wind River Basin to mix things enough to limit the
overall timing of the freeze, but this airmass is cold enough to
overcome most of this. Freeze Warnings are in effect tonight 
across central Wyoming, where freezing temperatures have not 
yet been reached.

The main pattern this weekend is a broad H5 ridge across the 
Rockies, bringing moderating temperatures and deflecting the 
storm track back into southern Canada. The main impact will be
which way the winds are from. Winds Saturday will be from the
southwest, bringing the warmer air back into the region. Sunday
a weather system passes across southern Canada, switching winds
back from the north. While no cold air will return with these
winds, it will be enough to bring temperatures back to near
normal around 60 degrees. The next weather impact across western
Wyoming still looking to be sometime Tuesday, when the ridge
is broken down by a trough along the Rockies, bringing more
moisture back from the southwest.

&&

.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...
Issued at 1105 AM MDT Thu Oct 15 2026

There is high confidence in dry conditions through at least 18Z 
Friday. Clouds will gradually clear across Wyoming Thursday 
afternoon, with MVFR to low VFR clouds occurring at and around KCPR 
through 20Z. Breezy north winds at KCPR, KRIW, KRKS, and KWRL are 
expected through 01Z, at the latest, before becoming 12kts or less. 
Winds at all other terminals are forecast to be light (12kts or 
less) the entire TAF period. There is a 10 to 20 percent chance of 
fog or low cloud development beginning around 12Z Friday at KJAC, 
KRIW, KRKS, KPNA, and KBPI. There is no mention in TAF at this time 
given the very low confidence.

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...
Freeze Warning from 11 PM this evening to 9 AM MDT Friday for 
WYZ005-006-010-011-016>020-028>030.

&&

$$

DISCUSSION...Straub
AVIATION...Gerhardt