911
FXUS65 KRIW 300805
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
205 AM MDT Sat May 30 2026

.KEY MESSAGES...

- An approaching weather system will bring a good to likely
  chance of showers to much of the area this morning, with most
  rain across western Wyoming through the day today. Rain
  chances will spread into the central basins and across the
  south this evening.

- Accumulating snow is likely today over the western mountains
  and over the northern mountains Sunday, especially above 9500
  feet.

- Temperatures will be much cooler today and Sunday as a result
  of the widespread rainfall, rebounding next week.

&&

.DISCUSSION...
Issued at 144 AM MDT Sat May 30 2026

Showers will continue to increase early this morning as the upper
level low approaches, mainly occurring over western and southern
portions. A sfc reflection of the low will develop near La
Barge/Farson by mid-morning and track to the northeast over the
Divide and into the Wind River Basin through the rest of the morning
into the early afternoon. Showers will rotate to the northwest
during this time, with showers being roughly confined along and west
of a Cody-to-Rock Springs line. Dewpoints will drop into the middle
30s over Natrona County, eastern portions of Fremont County, far
southern portions of the Bighorn Basin and Johnson County by 21Z as
a result of southerly winds shunting the available moisture
northward. Most areas east of the Divide are likely to stay dry
during the afternoon. Northern portions of the Bighorn Basin and
Johnson County will be the exceptions, with Johnson County having
the higher chances. A boundary will be in place that could provide a
trigger for any shower/storm to develop in this area, but will
quickly move northward due to the aforementioned southerly winds
pushing the boundary northward. The potential for any strong storm
will be in this area, with forecasted CAPE values of 1000-1500 J/kg
and LI values < -6. Shear will not be strong, so instability will be
the main driver for any severe storm. Otherwise, isolated to
scattered thunderstorms will be embedded within the aforementioned
shower activity over the west this afternoon.

The upper level low will slowly track over the Cowboy State through
the overnight hours tonight, reaching the northeast corner of the
state by 12Z Sunday. Showers and will continue over western portions
and Sweetwater County early in the evening, with additional showers
developing over the Bighorn and Wind River Basins after 06Z on the
backside of the low. Showers will increasingly become confined over
northern portions after 12Z Sunday as the upper low continues its
progression over eastern MT/the western Dakotas through the day.
Winds will increase across the CWA Sunday, as the gradient tightens
in the wake of the departing low. Gusts of 25 to 35 mph will occur
through much of the day, quickly decreasing through the evening.

Rainfall amounts over 0.10" from today through Sunday are still
forecasted to occur along and north of a Kemmerer-to-Riverton-
to-Kaycee line, with far southwestern portions of Sweetwater
County included. The heaviest amounts of 0.75 to 1" are still
expected over northern and northwestern portions of the CWA.
Flooding or rain-on-snow is not expected from this event, as
most snow in the 9000 to 10000ft range (SnoTel sites) is gone
already.

Isolated showers and thunderstorms will be possible Monday, as a
shortwave moves over the Cowboy State. Winds aloft will be
southwesterly as a trough develops over the Northern Rockies from
the remnants of today`s upper low. Most of the convection looks to
develop over the western mountains between 19Z and 21Z and quickly
push eastward over areas east of the Divide and Sweetwater County.
Additional showers will move over northwestern and northern portions
late in the afternoon into the evening, as a second shortwave
rotates through the base of the trough. Tuesday looks to stay mainly
dry, with west-southwest winds aloft keeping any potential
convection over far eastern portions of the state. Showers and
thunderstorms will be possible again Wednesday and Thursday, with
dry conditions returning for Friday. Temperatures will be above
normal these days, with highs in the upper 70s into the 80s.

&&

.AVIATION /06Z TAFS THROUGH 06Z SUNDAY/...
Issued at 1112 PM MDT Fri May 29 2026

The weather system pushes through the area over the next 24 hours,
with widespread rain and thunderstorm chances. Conditions will
frequently change between VFR and IFR at most terminals through the
TAF period. Terminals with the least impacts will be KCPR, KRIW, and
KLND. Wind will be gusty, especially with convection Saturday
morning through Saturday evening. As the area of low pressure tracks
through central Wyoming, wind will be shifting directions with
it, which is illustrated in the many changes in wind direction
in the TAFs. Mountain obscuration will become prevalent tonight,
especially around western terminals, and persist through the
TAF period.

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...LaVoie
AVIATION...LaVoie/Rowe