763
FXUS65 KRIW 211906
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
1206 PM MST Fri Feb 21 2025

.KEY MESSAGES...

- Seasonal to warm temperatures and dry today.

- 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.

- Snow chances return to western Wyoming Sunday as a weak
  weather system passes. Lower elevations/valleys may see rain
  or rain/snow mix.

- Gusty to strong winds Sunday through Tuesday, with the
  strongest winds over the mountains and the Wind Corridor
  (roughly Rock Springs to Casper, including South Pass).

&&

.UPDATE...
Issued at 1204 PM MST Fri Feb 21 2025

Temperatures have been a bit warmer than previously forecasted, so
have bumped up highs for today in some areas. Highs this
afternoon are generally in the mid-30s to mid-40s. Otherwise,
the forecast remains mostly unchanged, with dry conditions
expected today.

The next weather system is still on track to arrive over western
Wyoming starting Sunday. This system will bring gusty winds to
portions of the area Sunday through Tuesday. The locations of focus
are the mountains and the Wind Corridor from roughly Rock Springs to
Casper. Gusts in excess of 50 mph look possible, with gusty winds
continuing overnight in that time period. Will have to keep an eye
on model trends to see if/when any wind highlights would be
needed.

&&

.DISCUSSION...
Issued at 1230 AM MST Fri Feb 21 2025

IR currently depicts clearing skies across much of the state as
upper level ridging builds in from the west. Some cooler cloud
tops across far southern reaches of the CWA along the Colorado
state line with some light lingering snow flurries pushing out.
The main finger of the PFJ continues to stay to the northeast
diving into the Great Plains keeping the colder temperatures
away. The weak distortion of the jet diving south of the CWA
has supported this previous disturbance that now will push to
the southeast giving way to tranquil weather conditions for
Friday and into the weekend. Increasing upper level convergence
will allow for higher pressure at the surface and warming
temperatures even into early next week. As a result, the main
concern will be for ice jamming and flooding for area in
northern Bighorn Basin and Johnson County due to the recent
snowpack in lower elevations. Temperatures east of the Divide
will push into the 40s Friday and Saturday and 50s to near 60
Sunday through Tuesday. West of the Divide will remain in the
30s for much of this time as the next disturbance will start to
affect these areas come Sunday through mid week.

The main PFJ dips further south across Montana to northern
reaches of Wyoming by Sunday afternoon giving way to the Pacific
northwest moisture once again. This will increase snow chances
west of the Divide, mainly for the western mountains through mid
week. A mix to even just liquid precipitation possible for the
lower valleys as temperatures could remain above the freezing
mark for much of this period. Time will tell, but a forward look
on snow accumulations look to be modest at best to possible
advisory level criteria for the western mountains to include the
main passes as per usual with the zonal westerly flow. The main
trough looks to pass through the rest of the state to the east
late Tuesday and into early Wednesday, which gives really the
only chance for precipitation east of the Divide in the long
term period. With the warmer temperatures above freezing
(although cooler Tuesday and Wednesday) liquid rain the likely
precipitation for the lower elevations and likely snow for the
Bighorns. Otherwise, ridging builds back in for the remainder of
the week and into the following weekend with decreased
divergence aloft looking to be a possible omega block to end the
rest of the month and into March. Winter is still not done, but
it is in its waning hours in the longer term outlook.

&&

.AVIATION /18Z TAFS THROUGH 18Z SATURDAY/...
Issued at 1033 AM MST Fri Feb 21 2025

Little to no aviation concerns weatherwise during the next 24
hours. Clouds continue to move away from WY, with quickly
thinning clouds at KRKS. Remaining sites remain clear into the
overnight hours. A few cirrus will start to sweep in from the
northwest late tonight into Saturday morning. A few areas could
get breezy this afternoon, mainly at KRKS, KCPR, and KDUB, but
gusts today will remain below 20kts. Windier Saturday with more
frequent gusts to 40kts at KCPR.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

UPDATE...Wittmann
DISCUSSION...Lowe
AVIATION...Straub