695
FXUS65 KRIW 280732
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
132 AM MDT Mon Sep 28 2026

.KEY MESSAGES...

- A weather system moving across the area will bring areas of
  showers and isolated thunderstorms today into this evening.

- Locally heavy rain will be possible with any shower or
  thunderstorm today, although the chance of flooding is low.

- Largely tranquil weather is then expected for most of
  remainder of the week, with only a couple of chances of light
  showers. Temperatures will continue to average near to above
  normal.

&&

.DISCUSSION...
Issued at 129 AM MDT Mon Sep 28 2026

We are currently getting some much needed moisture across the area
with some areas of showers and isolated thunderstorms. This is
courtesy of a shortwave moving toward the area. It is getting an a
assist from a 95 knot jet streak that is approaching southwestern
Wyoming and will cross southern Wyoming this afternoon and evening,
putting much of the area in the left front quadrant of it to enhance
lift somewhat. As a result, almost all areas will have a chance of
showers today. There will also be some embedded thunderstorms.
However, with cloud cover around the area, surface instability may
be limited. The main threat from any storm would be locally heavy
rain, with precipitable water values generally running anywhere
from 125 to 150 percent of normal. A mitigating factor will be
that there will be steering flow, so any storms will have decent
motion and not be able to anchor. With more cloud cover,
temperatures will also run around 5 to 10 degrees cooler than
Monday. Coverage of showers and thunderstorms should decrease
after sunset, ending generally from northwest to southeast,
although with the jet still in the area overnight, isolated
showers and thunderstorms may linger south of a Casper to Rock
Springs through the night.

And, we could see some higher elevations snow from this. Any
accumulation would likely be restricted to above 11000 feet though.
The highest elevations of the Wind River Range, like the Gannett
Peak, have a 1 in 2 chance of seeing 3 inches of new snow. There
should be little or no impact to travel though.

We should then enter a quieter period of weather as ridging builds
into the area from the west, pushing drier air into western and
central Wyoming. There may be just enough leftover moisture for some
isolated showers in southern Wyoming, but this looks like the
exception rather than the rule. Following that, things look mainly
dry through the week and even into the weekend. A large majority of
the guidance keeps the moisture associated with an upper level
low and the remnants of Hurricane Polo to the south of the area
through the forecast period.A weak cold front will move into
northern and central Wyoming Wednesday night. This front is
moisture starved though so it will likely only bring some
clouds and somewhat cooler temperatures and a gusty breeze,
especially to northern Wyoming. Another front may move through
Friday night or Saturday, but again it has little moisture to
work with so any showers would be isolated with the only impacts
somewhat cooler temperatures and some gusty breezes.
Temperatures will generally average above normal, with Thursday
and Sunday looking like the coolest days behind the front. But
even here, temperatures will only fall back to near normal
levels. So, once we get past the next 24 to 36 hours, things
look fairly uneventful as we head into October.


&&

.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...
Issued at 950 PM MDT Sun Sep 27 2026

A weather system will pass through the area over the next 24 hours.
This will lead to multiple rounds of rain showers, rain, and
isolated thunderstorms through Monday afternoon. The rain will
gradually subside Monday evening as the weather system slides south
and east of the area. Conditions will predominantly remain VFR,
although will drop to MVFR at times during rain and storms. Brief
IFR conditions will be possible in the heaviest showers and
strongest storms. Ceilings are likely (70%) to drop to the upper end
of MVFR at KPNA Monday morning into early Monday afternoon.

Wind will be highly variable with numerous showers and isolated
storms through most of the TAF period. Wind should stabilize and
become light after sunset Monday. Sporadic to frequent mountain
obscuration will occur during the TAF period. It will be most
prevalent Monday morning.

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.

&&

$$

DISCUSSION...Hattings
AVIATION...Rowe