Riverton, Wyoming 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

515
FXUS65 KRIW 050344
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
944 PM MDT Sat Jul 4 2026

.KEY MESSAGES...

- Dry conditions reign across the region this Independence Day.
  Warm with light wind for this evening`s festivities.

- Daytime highs warm Sunday with only a few showers or perhaps a
  thunderstorm over northwest mountains, mainly in the mountains.

- Hot temperatures, about 6 to 12 degrees above normal, early
  next week with an increasing chance of afternoon thunderstorms
  both Monday and Tuesday.

- Drying out late next week and still hot. Temperatures may be
  the hottest of the season late next week into next weekend.

&&

.UPDATE...
Issued at 100 PM MDT Sat Jul 4 2026

A sunny sky across the forecast area this Independence Day with only
mountain cumulus drifting eastward into the nearby foothills/basins.
Towering cumulus over the Uinta Range will stay along or south of
the Wyoming border. Therefore, dry conditions prevail Saturday
afternoon through midday Sunday. A shortwave passing through the
Canadian Rockies draws a bit more moisture northward across the
northwest portion of the forecast area Sunday afternoon. Instability
and mid-level moisture should be sufficient to generate some weak
convection late Sunday across the northwest mountains. Sunday high
temperatures rise slightly, climbing to 5 to 10 degrees above normal
The passing shortwave does nudge a front, accompanied by little more
than a north wind shift, through northern Wyoming Sunday evening.

&&

.DISCUSSION...
Issued at 140 AM MDT Sat Jul 4 2026

Happy Birthday to the United States of America! It is very fitting
as I am starting this discussion that "America" by Neil Diamond is
playing on the radio. We are also having some natural fireworks
right now in the form of the Northern Lights. It is up to a G3
as I write this around 1 am so you can see it with the naked eye
if you let your eyes adjust.

All in all, the weather looks pretty good across the area for July
Fourth. A shortwave ridge looks to have timed itself just about
right. We will have upper level divergence in place over the
area. And for the first time in a while, surface CAPE is just
about nonexistent. There are a couple of thin areas over
northern Johnson County, far southern Sweetwater County and a
few of the mountain ranges but nothing more than 100 J/kg.
Lifted indices are generally positive as well. Below normal
precipitable waters (generally around 20 percent below normal)
will also be over the area today. All this adds up to very
small chances for showers and thunderstorms. I can`t rule one
out at the above mentioned locations this afternoon, but the
chance is maybe 1 out of 20. Otherwise, it will be warm today.
Not hot as a firecracker, but a few degrees warmer than
yesterday, with many locations east of the Divide rising into
the 90s. Dry conditions should continue through tonight and into
Sunday morning as well.

We will turn the heat up on Sunday as flow turns southwesterly. This
could be the first day of 100 degree temperatures in portions of the
area. Ensemble guidance gives around a 2 in 5 chance in places like
Greybull, Basin, Worland and Thermopolis for example. Temps in
the middle to upper 90s will be fairly widespread east of the
Divide though with 80s in the lower elevations west of the
Divide. The chance of convection returns as well, but it is
rather limited. There is good model consensus that most of the
forcing will remain north of the state over Montana. We do have
some small chances in northern Wyoming, but the chance is less
than 1 out of 5. Most areas will see nothing. As for fire
weather, with the hot temperatures and very low humidity (down
to 10 percent or less for many east of the Divide), it will be
elevated. However, wind should remain light to moderate, so
critical fire weather is not expected.

The chance of convection increases for Monday and Tuesday as a
couple of shortwaves pass near the area. There are still
disagreements with how widespread the convection will be
though. The official forecast leans more toward the ECMWF model
which is wetter, but this would likely be the wettest it would
be. Northern Wyoming would be more under the gun for Monday,
with Tuesday being more active as somewhat deeper moisture
moves into the area (precipitable water values may climb to 150
percent of normal). With more cloud cover, temperatures may be a
bit cooler, especially on Tuesday with more widespread showers
and storms.

Tuesday looks to be the peak in coverage of showers and storms.
There will still be some around Wednesday, but less than on Tuesday.
Following that, chances of precipitation will begin to decrease as
the pattern flips from this week. For much this week, we have had
troughing over the western United States with a very strong ridge
over the eastern United States, bringing record heat.
Indications are this will switch to a mean ridge over the
western United States, and potentially a very strong one. Some
guidance shows a 6000 meter ridge (at 500mb) centered over
Wyoming late next weekend into early next week. It is still a
long way off, but the NBM ensemble is giving a greater than 1 in
2 chance for high temperatures over 100 next weekend for areas east
of the Divide below 5200 feet. Again, this is a long way off
but we have to watch this. We are likely looking at the hottest
weather over the year for late next week and next weekend, with
little chance of storms as well. Mid July is typically the
hottest time of year, and this will be no exception.

&&

.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
Issued at 942 PM MDT Sat Jul 4 2026

VFR conditions prevail through the TAF period. Scattered rain
showers and isolated thunderstorms will develop Sunday afternoon,
mainly across northwest Wyoming. Little to no precipitation will
reach the ground with these showers and storms. Main concern is
strong to very strong downdraft wind. Gusts could reach as high as
50 knots with the strongest showers/storms. The only terminals with
a high enough chance for impacts to mention in the TAFs are KJAC and
KCOD with PROB30 groups for Sunday afternoon. There is a low chance
(15%) of a shower or storm at KWRL late Sunday afternoon into Sunday
evening.

A very weak cold front will drop into northern Wyoming Sunday
evening into Sunday night, with wind becoming northerly behind the
front. In general wind will remain 10 knots or less through the TAF
period.

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

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

UPDATE...CNJ
DISCUSSION...Hattings
AVIATION...Rowe