338
FXUS65 KRIW 032153
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
353 PM MDT Thu Apr 3 2025

.KEY MESSAGES...

- Isolated snow and rain showers are expected through this afternoon.

- Snow chances will increase late this evening as a cold front drops
  south into the area. Light snow is expected for much of the
  area through Friday, especially east of the Divide.

- Gusty north winds accompany the front as it moves south through
  Friday morning.

- Drier and warmer conditions return for the weekend and into
  next week.

&&

.UPDATE...
Issued at 320 PM MDT Thu Apr 3 2025

A cold front will drop south into Wyoming late this evening. This
will return snow chances from north to south overnight. One change
with the latest forecast is a slight increase in snow accumulations
east of the Divide through Friday morning, owing in part to a longer
period of upsloping northerly flow during this period. While most of
the area will still see an inch or less, upslope-favored locations
have the potential to see a little more. This includes Lander, which
has around a 30% chance of seeing more than 2 inches.

Casper is another location to watch given the upslope potential and
slightly better moisture availability there. Accumulations will vary
with the terrain, with around a 40% chance of seeing more than two
inches on the north side of town and around a 75% chance across the
south side near Casper Mountain. Casper Mountain will accordingly be
on of the most favored locations, with around a 70% chance of seeing
at least six inches.

Otherwise, deterministic hi-res guidance has sporadically been
painting other areas with higher snowfall tonight through Friday
morning, but overall we have low confidence in these scenarios.
A gusty northerly wind will accompany the front during this
time, which may lead to travel impacts with any falling snow,
especially across central Wyoming and the I-25 Corridor through
northern Johnson County. The limiting factor for a more
impactful event will be the time of year - a higher sun angle
and warmer temperatures should lead to melting snow, especially
later in the morning.

&&

.DISCUSSION...
Issued at 1246 AM MDT Thu Apr 3 2025

Snow shower activity is diminishing across the eastern Bighorn
Basin and Bighorns into the early Thursday morning hours. The
longwave pattern continues to elongate the deep trough across
much of the Rockies from Montana down to Baja California. As
such, much less activity expected Thursday and Friday to end
the work week. However, with the diffluence aloft persistent
over the CWA, expect sporadic, isolated showers for northern
counties with higher elevation snow and lower valley rain. The
surface boundary along the Montana state line will sag a bit
further south Thursday afternoon and evening giving way to this
development by early to mid afternoon before dissipating
towards midnight with nighttime cooling. Nothing of significance
with this activity with limited accumulations outside the
highest terrain above any passes. Warmer temperatures Thursday
but a bit cooler slightly below average for this time of year on
Friday behind the aforementioned surface boundary.

Similar conditions Friday as the cold front picks up a bit more
steam as it starts to slide east and southeast with the movement
of the upper level trough. With a much broader difluent flow
aloft, expect limited shower activity east of the Divide mainly
lingering into the overnight hours ending by early Saturday
morning. The main finger of the PFJ extends into the upper
Great Plains as ridging builds in from the west across the upper
Rockies. Increasing convergence aloft will give way to mainly
dry conditions and a warming trend for the remainder of the
weekend and into next week. Strengthen mid and upper level
heights allows for well above average temperatures for all of
next week seeing 60s to even 70s once again east of the Divide
and into the 50s to near 60 westward.

The upper level ridge looks to flatten out at the top due to the
PFJ sagging a bit further south out of the Pacific northwest and
through Montana. As such, some isolated chances for
precipitation late Tuesday through early Thursday, mainly
across northern sections of the CWA as the aforementioned PFJ
remains to the north in Montana. Beyond that, strong model
agreement on ridging building back in place and remain so
through the following weekend. Long term outlooks depict warmer
and dryer than average conditions to continue even beyond the
middle of the month, more than likely through the end as well
nearing the new month of May.

&&

.AVIATION /00Z TAFS THROUGH 00Z FRIDAY/...
Issued at 353 PM MDT Thu Apr 3 2025

Convective rain/snow showers should end shortly after sunset. A few
showers are possible over the mountains around KJAC over the next 24
hours, but no impacts to KJAC terminal expected at this time.

A weather system dropping southward will bring upslope snow to KCPR
and KLND as well as KCOD, moving from north to south. With recent
models trends, have also prevailed snow at KRIW. All areas with snow
will likely see MVFR to possibly IFR conditions for a short period
of time. With less confidence at other airports, we have elected to
go with PROB30 groups rather than prevailing. All snow should end
after around 22Z Friday near TAF sites with VFR conditions returning.

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...Myers
DISCUSSION...Lowe
AVIATION...Hattings