Mills, Wyoming 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

261
FXUS65 KRIW 221520
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
820 AM MST Sat Feb 22 2025

.KEY MESSAGES...

- Seasonal temperatures today with mainly dry conditions.

- Strong winds Sunday through Tuesday afternoon, especially
  across the Absaroka Mountains and into the Cody Foothills. A
  High Wind Watch is in effect for these areas Sunday and
  Monday.

- Snow moves into western Wyoming Sunday morning, continuing
  through Tuesday, though the heaviest snow falls Sunday
  afternoon through Monday morning. Western lower
  elevations/valleys could see rain or rain/snow mix.

- Continuing to watch for the possibility of ice jamming and flooding
  Sunday through Tuesday across the Bighorn Basin and Johnson
  County. This is due to warming temperatures and current
  snowpack in those areas. &&

.UPDATE...
Issued at 820 AM MST Sat Feb 22 2025

No major updates to the forecast this morning. It will be windy
across the central mountains and the Wind Corridor (Rock Springs to
Casper) this afternoon, with gusts in excess of 30 mph. A High Wind
Watch remains in effect for the Absaroka Mountains and Cody
Foothills Sunday morning through Monday evening. Gusts may be as
high as 70 mph on the mountains, with the possibility of some of
those winds making it to the lower elevations near Cody and Clark.
Recent model runs show the strongest winds for these locations late
Sunday night into Monday morning.

Current models show snow chances picking up in the western mountains
late Sunday morning (10am-noon). Heaviest snow is currently expected
Sunday afternoon through Monday morning. Will wait for the next
model runs later this morning before deciding on any winter
highlights. Snow levels, at least Sunday afternoon, are favoring
rain or rain/snow mix for the western valleys.

&&

.DISCUSSION...
Issued at 254 AM MST Sat Feb 22 2025

Current (09Z) water vapor imagery shows broad upper-level ridging
building into the Intermountain West. A fetch of Pacific moisture
rounding the periphery of the ridge is allowing for increasing upper-
level clouds to make its way into Wyoming. Cloud cover today will
limit insolation across the area and keep temperatures slightly
cooler compared to yesterday. Despite this increased moisture,
height rises and a lack of forcing will keep most of the area dry
today. However, I cannot rule out light snow this afternoon in
higher elevations of the Western Mountains. Snow amounts will be
minimal with the highest amounts being up to 0.5 inch.

Tonight, the ridge will continue to expand with mostly zonal flow
returning to the region. A 700mb wind maximum situated over Montana
will shift south into northern Wyoming and bring with it Pacific
moisture by Sunday afternoon. The deep zonal (westerly) flow is
favorable for snow chances across the Western Mountains through mid-
week. In the Western Mountains, there is a 70-80% chance of snow
amounts greater than 6 inches (minimum amount for a Winter Weather
Advisory) through early Tuesday morning. Snow amounts greater than
10 inches drops considerably to around 30% through Tuesday morning.
Snow will be confined to the higher elevations as temperatures
across the western Valleys are forecast to be in the upper 30s to
low 40s. Therefore, liquid precipitation can be expected in the
western Valleys.

Locations east of the Divide Sunday through Monday afternoon can
expect mainly dry weather with wind. The westerly 700mb wind
maximum, a tight pressure gradient, and a sharp 700mb temperature
gradient across northern Wyoming will allow for high wind potential
Sunday through Monday afternoon across the Absaroka Mountains and
the Cody Foothills. A High Wind Watch has been issued for these
areas for west winds 30 to 40 mph and gusts up to 70 mph. The watch
is in effect from early Sunday morning through Monday afternoon.
Strong winds cannot be ruled out for South Pass, over mountains, and
the Wind Corridor during through Tuesday. However, confidence is
much lower in reaching High Wind criteria due to not as favorable
flow.

Confidence is high in warmer temperatures east of the Divide with
highs in the 50s for lower elevations Sunday through Tuesday. This
brings continued concern for ice jamming and flooding for areas
across the northern Bighorn Basin and Johnson County.

There is consensus amongst guidance in a shortwave dropping through
Wyoming Tuesday into Wednesday. With the available Pacific moisture,
this brings the next chance for precipitation (both frozen and
liquid) to western and northern Wyoming. High elevations can
anticipate snow and the Bighorn Basin will see rain chances with
this system. Ensemble guidance is in agreement in ridging builds
back into the region Wednesday through the end of the work week.
This ridge will cut off available moisture for the Intermountain
West and keep precipitation chances very low (less than 10%
chance).

&&

.AVIATION /12Z TAFS THROUGH 12Z SUNDAY/...
Issued at 345 AM MST Sat Feb 22 2025

VFR conditions for the entirety of the period for all TAF sites.
Some lingering low stratus for JAC coming off lake through
sunrise possible but only carrying in tempo as it is not
prevailing at this time. Otherwise, light winds will increase
steadily through the day, at COD/CPR/RKS after 15-19Z, expanding
to RIW with the northwest valley flow after 00Z. Winds will ease
after 06Z for all but COD that will continue to see the westerly
gap flow into Sunday and beyond, only increasing into early next
week. Increasing clouds this afternoon after 19Z lasting through
the end of the period due to the next system coming out of the
Pacific northwest. Increasing snow chances west of the Divide
into the next TAF cycle for Sunday afternoon and evening but
otherwise, dry for this 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...
High Wind Watch from late tonight through Monday afternoon for
WYZ002-003.

&&

$$

UPDATE...Wittmann
DISCUSSION...Gerhardt
AVIATION...Lowe