587
FXUS65 KRIW 052245
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
345 PM MST Wed Feb 5 2025

.KEY MESSAGES...

- High wind warnings along and east of the Divide, light western
  mountain snow and some low valley rain today.

- Quiet but a bit cooler Thursday.

- Next system brings in mountain snow and possible valley rain
  Thursday night into much of Friday.

- Cooler over the weekend with even colder temperatures for next
  week.

&&

.DISCUSSION...
Issued at 1132 AM MST Wed Feb 5 2025

IR currently depicts some warming cloud tops across the CWA,
cooling further northeast with the main PVA anomaly of the
passing shortwave. WV shows the main PFJ pushing zonally across
the southern half of the state with 150+kt jet max helping to
mix to the higher elevations. Heating this afternoon will aid in
mixing the stronger boundary layer winds to the surface
producing the high wind warning criteria winds across the wind
prone areas from South Pass to Casper. Slightly less with less
confidence for the Absarokas and Cody Foothills but strong/close
enough to remain valid through the afternoon and evening hours.
The retreating warm front to the northeast is helping to bring
in these warmer temperatures and mixing of the 700mb temps to
the surface. Cold air across the Cody Foothills/upper Bighorn
Basin has remained in place this morning but is started to mix
out with clearing to help aid in a nice warmup/recent snowmelt
this afternoon. In all, this will be short lived as the main
shortwave progressively passes to the east.

As such, cooler temperatures for Thursday as winds diminish
overnight into the morning hours as the gradient slackens but
remains elevated until closer to the afternoon hours. Breezy
winds still expected but not near as much as Wednesday afternoon
ahead of the next short wave spinning around the main low off
the Pacific northwest coast. With the near zonal upper level
flow, the main finger of the PFJ pushes a bit south with the
divergent zone across west of the Divide by late Thursday
evening before extending east into Friday morning. Snow west of
the Divide expected until daytime heating late morning Friday
where a mix to just rain is likely as temperatures push above
freezing in the western valleys. As such, east of the Divide
will most likely see just rain with the timing of precipitation,
keeping any snowfall to higher terrain. WPC totals don`t
account for the precipitation being more rain/mix in the lower
elevations and thus, giving higher snow outputs. Best snow
accumulations to advisory level will be for the Tetons/Gros
Ventres, Wyoming/Salts, and western Winds as per usual with the
zonal flow with 6 to 10 inches the best probabilities of 70-90
percent. PWAT values of .1 to .2 inches east of the Divide for
the basins, and likely all rain during daylight hours late
Friday morning through the afternoon.

Regardless, with time to refine this Friday forecast, all models
indicate the bulk of the precipitation with this shortwave to
push out Friday night into Saturday with just some lingering
showers along the I-25 corridor. With the active pattern but
weaker signals for the weekend, expect some light western
mountain snow periodically as colder air pushes across the CWA
behind a Pacific cold front. The stronger bit of cold air energy
will push in late Sunday night into early next week with more of
an arctic surge being more of a continental source. Snow will be
the precipitation type at that point but no indications of a
strong snowfall at this time. Quite a bit colder temperatures
will follow for much of next week but longer term models bring a
slow warming trend by week`s end into the next weekend as
ridging builds in from the west and southwest.

&&

.AVIATION /00Z TAFS THROUGH 00Z FRIDAY/...
Issued at 344 PM MST Wed Feb 5 2025

Gusty winds across the area will decrease through the evening and
early overnight hours. A mostly clear sky persists through the
night for most locations, with increasing high clouds Thursday
morning ahead of the next weather system. Precipitation chances
will begin to increase across western Wyoming Thursday
afternoon, with about a 20% chance at KJAC. Better chances move
in near the end, and after, the TAF 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 Warning until 8 PM MST this evening for WYZ002-003-
016-019-020.

&&

$$

DISCUSSION...Lowe
AVIATION...Wittmann