844
FXUS65 KRIW 090343
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
943 PM MDT Wed Oct 8 2025

.KEY MESSAGES...

- A few late-day showers and thunderstorms are expected across
  southwestern Wyoming on Thursday. Otherwise, another afternoon
  of elevated fire weather conditions is expected Thursday.

- Precipitation chances increase Friday through the weekend as
  moisture returns to the area. Cooler temperatures and mountain
  snow expected Saturday night and Sunday.

&&

.UPDATE...
Issued at 1234 PM MDT Wed Oct 8 2025

Clear skies are noted across the area early this afternoon as a dry
southwesterly flow sets up over Wyoming. Little change to the
forecast was made, with the main concern in the short term being
elevated fire weather conditions for much of the CWA through the
afternoon. This will be most notable along the Wind Corridor where
gusts will approach 30 mph and humidity will drop below 20 percent.
Otherwise, the end of week system remains on track, with a much more
active pattern returning to the area this weekend.

&&

.DISCUSSION...
Issued at 229 AM MDT Wed Oct 8 2025

Another chilly start to the day across the Cowboy State.
Temperatures this morning are ranging from the mid to upper 20s west
of the Divide and mid 30s east of the Divide. Fortunately, a warming
trend really kicks into gear today with highs reaching the mid
60s to low 70s. These warm temperatures persist through the rest
of the week as high pressure prevails over the region. High
pressure will also keep things dry over the next few days, but
this may lead to near elevated fire weather conditions today.
The main area of concern is along the Wind Corridor from Rock
Springs to Casper and into Johnson County. This area will see
min RH values around 20 percent with periodic wind gusts of 20
to 30 mph this afternoon. Winds lighten up overnight with dry
and mostly quiet weather prevailing through most of Thursday.

The forecast starting late Thursday into the weekend remains tricky
as cooler and unsettled weather looks to return to the CWA. There
are multiple moving parts that will each interact with one another
over the next couple days. The first is the area of high pressure
that has brought warmer and drier conditions to the region. The
second is a large potent low pressure system that moves into the
PACNW by the weekend. The third component is an area of
tropical moisture that will be moving northward from Mexico.
Last, but not least is a trough that will dig south from
western Canada into the PACNW by the end of the weekend. Now
timing for all these components still remains variable as models
have recently been a little too quick in the progression of
things. So now, how do all these pieces interact and effect our
CWA?

Starting with the high pressure that is gradually shifting to the
east as we progress through the week. The center of the high will
settle over portions of Texas and New Mexico. The anticyclonic
flow will funnel tropical moisture associated with Hurricane
Priscilla and its eventual remnants across parts of the Desert
Southwest by Thursday. This plume of monsoonal-like moisture
looks to eventually make its way into the southern CWA late
Thursday. This may lead to a few isolated showers and storms
Thursday evening across Sweetwater, southern Lincoln, and
Sublette Counties and possibly further north by the early hours
on Friday. The bulk of the moisture arrives by Friday,
spreading further north across nearly all of the CWA. Friday
will likely be unsettled with chances for showers and storms as
above normal PWATs enter the region. Southwesterly flow persists
into Saturday aiding with the funneling of moisture across much
of the region. However, by the early hours on Saturday a trough
will begin to dig south over northern California/the Great
Basin, pushing eastwards through the day. This system should
provide some favorable upper level dynamics that look to
interact with the tropical moisture. All of this should combine
to create a push of precipitation Saturday afternoon and evening
across the CWA, starting from the southwest into central basins
and possibly northern areas. The nearing trough axis will
supply enhanced jet dynamics late Saturday into early Sunday
over western WY where flow looks to be the most favorable for a
period of upsloping. The trough will also bring with it colder
air leading to the possibility for accumulating snowfall over
western mountains. Lower elevations of western WY may see a
brief transition of cold rain to a wet heavy snow early Sunday
morning. It is still too early for an idea of how much snowfall
can be expected across the higher elevation, but a better idea
of what to expect should come to fruition over the next few
days.

To summarize, above normal moisture will enter the region late
Thursday and early Friday. This will lead to increased chances for
precipitation across much of the CWA for most of Friday. Widespread
chances for precipitation persist into Saturday with a nearing
trough further enhancing precipitation chances. By late Saturday
afternoon/early evening, favorable flow will focus across
western WY where a period of heavy precipitation may be
possible. Colder air is ushered into the area around this time
leading to accumulating snowfall across the western mountains.
Lower elevations likely see mostly cold rain, but may see a
brief period of wet snowfall early Sunday. Showers linger over
western WY for Monday with another potential disturbance
possible for the first half of next week. Confidence in timing
remains low from Saturday onward.

&&

.AVIATION /06Z TAFS THROUGH 06Z FRIDAY/...
Issued at 943 PM MDT Wed Oct 8 2025

VFR conditions, with relatively light winds through the period.
Clouds increase from the southwest later in the TAF period as
increasing moisture advects in the area. Therefore, increasing
clouds expected for western/southwestern terminals (KBPI, KJAC,
KPNA, and KRKS) later in the period. Models differ in the onset of
rain chances late in the period, but current consensus would have
the best chances occurring right at the end, or right after the
period. Therefore, has left any precipitation chances out of the
TAFs.

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...Dziewaltowski
AVIATION...Wittmann