Slide Lake Trail, Wyoming Weather Forecast Discussion

001
FXUS65 KRIW 280732
AFDRIW
Area Forecast Discussion
National Weather Service Riverton WY
132 AM MDT Sun Sep 28 2025
.KEY MESSAGES...
- Widely scattered (20-30%) showers and thunderstorms across
  western portions this afternoon and evening.
- Chances are low (10-20%) for locally heavy rain with the
  stronger storms this afternoon.
- Shower and thunderstorms will be possible over western
  portions again on Tuesday.
&&
.DISCUSSION...
Issued at 125 AM MDT Sun Sep 28 2025
Not much change in the forecast. 05Z satellite imagery shows clouds
beginning to increase from the south over Sweetwater and Lincoln
counties and the Upper Green River Basin. Weak virga showers are
also showing up on radar in these areas. Moisture/clouds will
continue to stream northward this morning and through the day today,
leading to widely scattered (20-30%) showers and thunderstorms to
occur over mainly western portions of the CWA through the afternoon.
Some of these showers/storms will spill over near Dubois, Meeteetse
and Cody, as the come off the east slopes of the Wind River and
Absaroka Mountains. Wind gusts of 40 to 50 mph will be the main
threat, as T/Td spreads will be around 40 degrees. Locally heavy
rain cannot be ruled out from the stronger storms either, as PWATs
of 0.6" to 0.8" will be in place by late this afternoon. This,
coupled with generally weak steering flow, could lead to brief heavy
downpours. Any remaining shower or storm is expected to end by
midnight (06Z), with isolated weak showers remaining possible
over the central basins through 09Z. Otherwise, temperatures
will continue to be above normal for areas east of the Divide
and near normal west of the Divide.
A cutoff low, that has been nearly stationary over the Desert
Southwest the last few days, will begin to fill today and get kicked
from a significant longwave trough over the EPAC. This trough will
be the focus for the next week. Showers and isolated thunderstorms
will be possible over the western mountains again, including areas
near Dubois and Cody. Otherwise, conditions will be somewhat similar
to today.
The longwave trough will move onshore over the West Coast Monday
night into Tuesday, filling and weakening as it does so. Showers and
thunderstorms will be possible over western portions Tuesday
afternoon as a result. A southwest flow pattern will Wednesday
through Friday, as a closed low associated with the longwave trough
will make little progression eastward due to a strong high center
over the mid-Mississippi River Valley. No embedded shortwave troughs
are expected to move over the Cowboy State Wednesday and Thursday,
keeping conditions dry. Elevated fire weather conditions do not look
as likely Thursday, as 700mb winds have decreased to 20-30 kt. Model
consensus begins to diverge by Friday due to this high center
(coincidentally, this will also likely affect the forecast for
Tropical Depression 9), with the ECMWF weakening both the high and
PACNW low and bringing widespread precipitation chances across the
CWA as the trough moves over the region. Strangely, the GFS is the
slower solution and keeps the low closed as it digs southward over
northern CA/NV. This would keep precipitation chances to western
portions of the state Friday afternoon into Saturday morning.
&&
.AVIATION /06Z TAFS THROUGH 06Z MONDAY/...
Issued at 1056 PM MDT Sat Sep 27 2025
VFR conditions are expected through the period. However, clear skies
early in the period will give way to high clouds overnight as a
system approaches. This will bring occasional showers to western
Wyoming overnight, though with most of this activity beginning after
sunrise Sunday. Showers and thunderstorm chances then increase at
KJAC, KBPI, KPNA, and KCOD through Sunday afternoon; these terminals
have PROB30 to account for this potential. Convection will be on the
decrease late in the period with most activity ending by 03Z Monday.
Otherwise, winds will increase slightly at KRKS and KCPR Sunday
afternoon with gusts to around 20 knots.
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.
&&
$$
DISCUSSION...LaVoie
AVIATION...Myers

NWS RIW Office Area Forecast Discussion