Mills, Wyoming 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

584
FXUS65 KRIW 181051
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
351 AM MST Sat Jan 18 2025

.KEY MESSAGES...

- Light snow showers linger across locations east of the Divide
  with minor additional snow accumulation expected.

- Cold temperatures have settled over the region and will remain through
  the first half of the upcoming week.

- Dangerously cold temperatures in the -10s to -20s are forecast
  across the CWA for Monday and Tuesday morning.

- Milder temperatures are forecast to return for the second half
  of the week with some uncertainty regarding the persistence of
  inversions over some basins.

&&

.DISCUSSION...
Issued at 123 AM MST Sat Jan 18 2025

Winter made a grand return to the Cowboy State Friday. An arctic
front moved across the state bringing widespread gusty winds and
snow showers. Moderate to heavy snow fell across central and eastern
portions of the CWA during the day Friday. Early snow totals range
from 1-3 inches across the Wind River Basin and Natrona County. The
jackpot looks to be along the Lander Foothills, where 4 or more
inches of snow fell. Light snow showers are expected to linger
through the early afternoon on Saturday mainly for locations east of
the Divide. Additional accumulations are forecast to be minor with
amounts ranging from a coating to 1 inch. Locally higher amounts are
possible along the Lander Foothills. Cold air settles across the
region through the weekend into the first half of the upcoming week.

Forecasting the extent of the upcoming cold is going to be tricky as
there are multiple small scale factors that can greatly influence
temperatures. These factors are cloud cover, wind, snow depth, and
elevation. These factors will first be seen with high temperatures
today, which are currently forecast to range from the single digits
to teens. Lingering snow showers east of the Divide will keep cloud
cover across much of the CWA. This cloud cover will greatly limit
the degree of daytime heating that many locations see. Clouds are
expected to gradually clear out overnight Saturday into Sunday
morning. This looks to be the real start of the frigid dangerous
cold, as forecasted Sunday morning lows are all sub-zero with values
in the negative teens for much of the CWA. As mentioned earlier,
there are a lot of small scale factors at play here and there is a
good chance that lows will be even colder than what is currently
forecasted. Having these components in mind, models are highlighting
Monday morning and Tuesday morning as having the best chances of
seeing the coldest temperatures. Current forecasted lows range from
the negative twenties to negative teens for both days. Probabilistic
guidance is pinpointing portions of the central Wind River Basin,
Natrona/Johnson Counties, Upper Green River Basin, and parts of
Jackson Hole/Star Valley as having the best chance of seeing lows
near or below negative 20 on these two mornings. Depending on these
smaller scale components at these locations, temperatures may end up
being colder if the perfect conditions are met.

At this time no cold temperature related highlights will be issued
tonight, but it will likely need to be revisited by the day shift.
There are some locations, specifically portions of Natrona/Johnson
Counties and some western valleys/basins that need to be monitored.
The main concern will be some breezy conditions which, when combined
with already cold temperatures, may lead to apparent temperature
values ranging from -25F to even -35F in some areas on Monday and
Tuesday morning.

Tuesday onward will see much of the arctic air begin to moderate, as
a brief period of ridging tries to build back in over the region.
Winds will increase ahead of this ridge with periodic gusts of 25 to
35 mph. Gusty winds look to be mainly from Casper to Rock Springs as
well as portions of the upper Wind River Basin. These winds will aid
in mixing warmer air towards the surface. Temperatures are looking
to warm back up across much of the CWA on Tuesday, but there may be
some exceptions to this. Lower elevation basins with fresh snowpack
will need to be monitored as stubborn inversions may limit how much
mixing makes it down to the surface. One area of note is the central
Wind River Basin, which based off previous events, has had
difficulty mixing out after inversions develop. So while many will
see warmer temperatures for the second half of next week, some
locations may be socked in with cold temperatures prevailing until
those inversions can be broken. The remainder of the week is looking
to see the active weather pattern continue. However, confidence
regarding impacts is still very low, as models are still uncertain
on tracks and timing of these potential disturbances.

&&

.AVIATION /12Z TAFS THROUGH 12Z SUNDAY/...
Issued at 344 AM MST Sat Jan 18 2025

West of the Divide...KBPI/KJAC/KPNA/KRKS Terminals

Light snow will return at KRKS around 14Z for a few hours,
bringing MVFR conditions back to the terminal. VFR conditions
are expected elsewhere as clouds begin to scatter out this
morning. Winds with a northerly component will occur through
much of the day. Winds will briefly turn westerly at KJAC around
22Z, before returning to the north after sunset. A similar
switch will occur at KRKS around 00Z and stay westerly through
the rest of the period. Clouds will continue to scatter out over
western WY this morning, reducing mountain obscurations.
Obscurations will return over the far western mountains after
04Z.

East of the Divide...KCOD/KCPR/KLND/KRIW/KWRL Terminals

Light lingers at KRIW/KLND and KCPR, with MVFR conditions. Snow
is expected to end by 18Z, with VFR conditions returning. The
exception will be KCPR, where MVFR ceilings remain in place
through 01Z. BKN-OVC FL020-080 will be common across the area
through the afternoon, with the lower end rising to 040 after
00Z. Winds will be much lighter, with gusts up to 20 kt expected
for a few hours at KWRL. Mountain obscurations will be common
through the day, clearing out through the overnight hours
tonight.

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...
Winter Storm Warning until 8 AM MST this morning for WYZ018.

&&

$$

DISCUSSION...Dziewaltowski
AVIATION...LaVoie