660
FXUS65 KRIW 142151
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
351 PM MDT Sun Sep 14 2025

.KEY MESSAGES...

- After a warmer and drier end to the weekend, unsettled
  conditions will return through early next week bringing
  additional shower and thunderstorm chances.

- Morning lows will continue to trend seasonably downward. Temperatures
  across basins west of the Divide may approach or drop below
  freezing Monday night and Tuesday night.

- A return to warmer and drier conditions is favored to end the
  week.

&&

.UPDATE...
Issued at 1128 AM MDT Sun Sep 14 2025

The forecast is on track today, with notably clearer conditions as
the previous wave departs to the east. Brief ridging has taken over
and will keep dry conditions through the daylight hours. The next
disturbance is evident over Oregon/Idaho and will approach this
evening. Model guidance continues to show showers arriving
overnight, moving north and east through Monday. Along with
convection, Monday will also see gusty west to southwest winds from
Uinta County through Natrona County as a surface low develops to our
northeast. Showers and thunderstorms will end for most Monday
evening, lingering later across northern Wyoming as the associated
midlevel low approaches.

&&

.DISCUSSION...
Issued at 209 AM MDT Sun Sep 14 2025

The broad trough continues to slowly try to shift east, with
multiple embedded impulses rotating through it. The latest wave
is sweeping into western Nebraska/South Dakota this morning,
with some wraparound precip trying to form back into Natrona
County. This precip has been very light, if reaching the ground
at all, and will quickly exit back to the east by midmorning.
The gap between systems today will allow most areas to see
partly to mostly sunny skies and warm temperatures back into the
70s and lower 80s.

WV imagery shows the next weather system currently coming ashore
across Oregon. This system will come rotating around the bottom
of the trough and into western WY late tonight, spreading the
next round of showers and thunderstorms into the region. Models
continue to bring this trough eastward, then stalling it across
western WY through Tuesday. This will continue the high
likelihood of showers and thunderstorms into Tuesday. With the
overarching trough nudging eastward as this arrives, the
remaining portion of the smaller system then shunts southward
late Tuesday and Tuesday night. This also brings modest
northerly flow behind it, bringing slightly cooler air into the
state. Temperatures will cool enough to approach near freezing
west of the divide in lower valleys and basins Tuesday night.

&&

.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 350 PM MDT Sun Sep 14 2025

Diurnal winds decrease this evening. An upper-level low begins
pushing into western Wyoming tonight, with impacts beginning at KJAC
around 06z. Main impacts with this initial push are rain shower
chances. PROB30 groups are included in TAFs to cover rain chance
timings. A secondary push is possible Monday afternoon, which
continues rain chances. Because of day time heating, thunderstorms
will be possible. Gusty outflow winds are the main hazards with
storms.

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.

&&

$$

UPDATE...Myers
DISCUSSION...Straub
AVIATION...Wittmann