043
FXUS65 KRIW 140444
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
944 PM MST Thu Nov 13 2025

.KEY MESSAGES...

- Winds will decrease through the evening, before increasing
  again after sunrise Friday morning.

- Showers return to western Wyoming on Friday, with isolated
  strong wind (55+ mph) possible in areas like Casper and the
  leeside of the Absarokas.

- A cooler and wetter pattern begins Sunday, lasting into next
  week, though details on timing and placement of rain and snow
  remain uncertain.

&&

.UPDATE...
Issued at 1146 AM MST Thu Nov 13 2025

No notable updates to the forecast for today. Temperatures are quite
warm for mid-November, with highs across the area in the upper 50s
to mid-60s. Gusty southwest winds occur from South Pass to Casper,
generally 25 to 35 mph. These winds also occur across the Absaroka
and Wind River Mountains, as well as portions of Yellowstone. A
shortwave is still projected to move through tonight and tomorrow,
increasing winds for those previously mentioned locations (with
lesser increases elsewhere). Rain/snow chances will also increase
across the western mountains and valleys after 2am MST, with the
best chances Friday afternoon. Overall amounts have not changed
much. The highest elevations of the Wind River Mountains have
increased slightly, but still only up to about 5 inch totals.

&&

.DISCUSSION...
Issued at 251 AM MST Thu Nov 13 2025

All in all, things look to remain quiet today as ridging will remain
in place over the area for Thursday as well. The only concern will
be gusty wind in the favored southwesterly flow areas, like Casper,
but with 700 millibar winds only around 30 knots, high wind is not
expected. Temperatures will remain very mild as well, in some cases
over 20 degrees above normal. A few places, like Casper, will make a
run at 70 and could break a record high today.

Things finally begin to take a more active turn on Friday as a
Pacific trough approaches the area. As for precipitation, this looks
more like a nuisance event then anything. The system does not have a
lot of moisture to work with. Ensemble guidance gives at most a 1
out of 3 chance of 3 inches or more of snow from Friday through
Friday night and this is only in the southern Absarokas where
impacts are small to non existent. Temperatures also look to
remain fairly mild, with 700 millibar temperatures only falling
to possibly minus 2, which would keep snow levels at 7500 feet
or higher and away from the valleys. The main concern looks to
be wind. The jet will be close to the Montana border, putting
much of the area in the favored right front quadrant for
downward forcing. The 700 millibar winds are borderline though,
only around 40 to 45 knots when I would like to see 50 to 55
knots. The areas with a greater than 1 in 2 chance of wind gusts
past 55 mph are generally restricted to the higher elevations.
I could see a stray gust over that in a place like Wyoming
Boulevard, but not widespread enough for any highlights. The
threat of higher wind should end Friday evening as the trough
moves through and the pressure gradient relaxes. This will also
bring a warm day, probably the warmest day of the period. The
best chance of seeing a 70 degree high is Friday, and if this
occurred at Casper, it would be the third latest 70 degree high
temperature in station history.

Ridging will build back over the area on Saturday, and bring a
mainly dry and somewhat cooler but still mild day. The next
potential weather maker then moves in for Sunday as an upper level
low moves onshore over California and moves toward the Cowboy State.
This system looks potentially more interesting as it crosses
the Rockies and could bring leeside cyclogenesis over Colorado
and wrap more moisture back into the area. There is not a lot of
cold air though and at this point this would be a rain event in
the lower elevations or possibly a rain / snow mix with snow
levels remaining above 6500 feet, so any impacts would be
restricted to the mountains. Another system then arrives early
next week, and this one is potentially cooler and may bring the
first accumulating snow to the lower elevations east of the
Divide. However, upper level lows are notoriously hard to
forecast, especially in regards to details this far out. So,
although confidence is high in a transition to a cooler and
wetter pattern next week, confidence is still very low in
regards to the details of placement and amounts of
precipitation.

&&

.AVIATION /06Z TAFS THROUGH 06Z SATURDAY/...
Issued at 940 PM MST Thu Nov 13 2025

VFR flight conditions continue through the entire TAF period with
SCT-BKN FL150-250 at times. KCPR will be the windiest terminal,
with gusts ranging between 25 kt to 35 kt starting at 09Z and
lasting through most of the forecast. At all other terminals,
winds are forecast to be 10 kt or less through at least 12Z.
Winds increase with gusts of 20-30 kt by 18Z at all terminals
except KWRL. Strong winds aloft will lead to LLWS over the
western mountain at the start of the forecast period, before
spreading to KCPR by 09Z and KCOD by 14Z. Confidence is lower
(30%) for LLWS at KJAC, so there is no mention at this time.
These strong winds will result in downsloping winds of 50 to 60
kt over the east slopes of the Wind River and Absaroka Mountains
between 06Z and 18Z. Similar winds will develop off the east
slopes of the Bighorns after 12Z.

There is a 30% chance of light rain at KJAC between 21Z-00Z Friday
afternoon with an associated lower chance (20%) for MVFR ceilings.
However, given the low confidence in exact timing and location,
PROB30 group reflects these precipitation chances. Marginal MVFR
ceilings will remain in place over KJAC and KPNA  after 00Z as
precipitation chances retreat northward. Mountain obscuration
will develop over northwestern portions after sunrise Friday
morning and spread southward to the rest of the wester mountains
by early afternoon. These clouds will remain in place through
the end of the forecast 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.

&&

$$

UPDATE...Wittmann
DISCUSSION...Hattings
AVIATION...LaVoie/Gerhardt