359
FXUS65 KRIW 041007
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
407 AM MDT Sun Oct 4 2026

.KEY MESSAGES...

- A beautiful autumn day is on tap today with a cool morning, a
  warm afternoon and a good deal of sunshine.

- Low humidity, warm temperatures  and a gusty breeze will
  bring elevated to potentially critical fire to portions of the
  area Monday afternoon. Daily to possibly all time monthly
  high temperatures are possible in the afternoon.

- Mainly dry conditions and above normal temperatures will
  continue through at least Friday.

&&

.DISCUSSION...
Issued at 1253 AM MDT Sun Oct 4 2026

This is around the time of year when those of us who have been in
Wyoming for a while start thinking about when the first snow is
going to fly. I can remember a few snowstorms before this date,
including a few damaging ones. That makes days like this one even
more precious. Today may be the perfect early autumn day. High
pressure will be over the area today. The result will be a cool,
crisp morning followed by a comfortably warm afternoon with lots of
sunshine. Wind should also remain fairly light as well, especially
by Wyoming standards. And, it falls on a weekend, so most people
will get to experience it. Enjoy!

Things get a bit more active on Monday. A Pacific trough will begin
to approach the area from the west. This will tighten the pressure
gradient somewhat and bring a gusty breeze, especially to the
favored southwest flow areas from east of Rock Springs through
Casper. This area has at least a 3 out of 4 chance of wind gusts
past 30 mph according to the NBM ensemble forecast, along with
areas like the Upper Wind River Basin and the Lee of the Absarokas.
With mean relative humidity on the NBM ensemble generally less
than 15 percent in these areas, we hoisted Fire Weather Watches
for this area from 12 pm to 6 pm Monday. However, elevated fire
weather will be possible elsewhere. And, with the warming,
downsloping flow, it will be an abnormally warm day for the
fifth of October. Most locations East of the Divide under 6000
feet in elevation have at least a 3 out of 4 chance of high
temperatures over 80 degrees. Most locations under 5000 feet
have a 1 in 2 chance of highs of 85 degrees or higher. There
will likely be some daily record high temperatures. A few
locations could get close or possibly break all time monthly
record high temperatures at well, which are generally in the mid
to upper 90s.

The pressure gradient should relax somewhat on Tuesday, so the
result will be less wind and as a result some improvement in fire
conditions, This should allow for temperatures to be a bit cooler,
but still well above average and possibly break some more daily
records. The trough will be passing to the south on this day. There
may be just enough moisture for a stray shower or thunderstorm in
Sweetwater County in the afternoon, but the chance is less than 1
out of 8 so we left it out of the forecast for now.

Warm and dry weather should continue through the remainder of the
workweek. The next chance for critical fire weather looks to be
Friday as a shortwave trough moves through the area na could bring
some gusty wind and low humidity. We may have a pattern change
following this as the trough breaks down and a more potent Pacific
system approaches from the west. It could arrive as early as
Saturday, but experience tells me the models are usually too fast
with Pacific systems this far out, so it is more likely for Sunday.
This is not certain, but odds are increasing of seeing some cooler
and possibly wetter weather for next weekend or early the
following week.

&&

.AVIATION /12Z TAFS THROUGH 12Z MONDAY/...
Issued at 406 AM MDT Sun Oct 4 2026

VFR conditions will continue through 12Z Monday with a mainly
clear sky. Wind will remain under 10 knots for most locations,
with the strongest wind in vicinity of KRKS where gusts to 12 to
15 knots are possible after 20Z until sunset.

Please see the Aviation Weather Center and/or CWSU ZDV and ZLC for
the latest information on icing and turbulence forecasts.
&&

.FIRE WEATHER...
Issued at 1253 AM MDT Sun Oct 4 2026

Low humidity will be around today, but wind should remain light
to moderate. A combination of humidity falling into the teens
and a gusty southwesterly breeze will bring elevated to possibly
critical fire weather Monday afternoon, with Sweetwater, Natrona
and eastern Fremont Counties the area of greatest concern.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
Fire Weather Watch Monday afternoon for WYZ279-280-289-300.

&&

$$

DISCUSSION...Hattings
AVIATION...Hattings
FIRE WEATHER...