814
FXUS65 KRIW 070402
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
Issued by National Weather Service Billings MT
1002 PM MDT Tue May 6 2025

.KEY MESSAGES...

- Isolated light showers linger around Natrona County into the
  early Wednesday morning hours. Cloud cover is slow to depart.

- A building ridge of high pressure late this week leads to dry
  conditions and a steady warming trend until at least Saturday.

- Much above normal temperatures, 10 to 20 degrees above
  seasonal averages, could allow for near-record breaking high
  temperatures and the first round of snowmelt runoff into
  mountain creeks and streams by the weekend.

&&

.UPDATE...
Issued at 144 PM MDT Tue May 6 2025

Much of the forecast remains unchanged as wrap around moisture
continues to move into portions of the state this morning leading to
periodic showers. Showery activity will linger into the
afternoon and evening before dissipating overnight. Temperatures
are forecast to gradually warm throughout the day and will
likely be warm enough for many locations to see a transition
back over to rain. Overall, forecasted highs for today will be
well below normal with the coldest values east of the Divide,
with temperatures in the upper 30s to mid 40s. West of the
Divide will see warming temperatures in the low 50s as cloud
cover scatters leading to brief periods of sunshine. Gusty winds
continue across southern WY with gusts of 35 to 45 knots at
times this afternoon before gradually weakening by the late
evening hours.

The remainder of the week continues to look mostly quiet with
ridging building in over the region. There remains the possibility
of some isolated showers over the next few days but most will remain
dry. Warmer temperatures are expected to build in with highs likely
becoming well above normal by the end of the week. Model guidance is
starting to hint at some locations mainly east of the Divide
reaching the mid 80s and possibly upper 80s. There is still time for
things to change but just how warm it gets will need to be monitored
as this may lead to some rapid snowmelt in the mountains.

&&

.DISCUSSION...
Issued at 208 AM MDT Tue May 6 2025

When I was growing up back in the times when dinosaurs roamed the
earth (the 70s and 80s for reference), I often entertained myself
after school by watching re-runs of old sitcoms. And one my
favorites was the secret agent parody Get Smart. And one Don Adams`
(the star of the show) catch phrases was "Missed it by That Much",
implying a close miss.

In regards to this morning, it was the snow. The cold came in a
little faster and deeper than I thought yesterday morning. The
result is bigger snow accumulations then I thought. Lander was
already up to 2 inches at midnight, and we have some accumulation at
the office as well. Most roads below around 5800 feet are mainly wet
though, including at our office where the parking lot has remained
just wet. We do have some slick roads above this though, with the
worst conditions over South Pass. Snow will continue through the
night. However, we can see the light at the end of the tunnel. All
guidance shows the heaviest precipitation ending around sunrise. In
addition, the strong May sun will have an impact, melting the snow
off most roads by mid morning and the warming temperatures and less
intense precipitation rates will see a lot of snow mix with or
change back to rain in the lower elevations. The chances of greater
than an additional inch of snow after 6 am are at most 1 out of 3 in
the lower elevations. There will still be some difficult conditions
over the passes in the morning though, so we will keep the
advisories up for now.  Showers will continue through the day,
although coverage will decrease, especially in the afternoon with
almost all of them over by midnight tonight. It will be another
cold day though, with many areas east of the Divide struggling
to reach 40 degrees. Most areas will also see the gusty wind
decrease through the day. The exception will be southern
Wyoming, especially Sweetwater County, where a decent pressure
gradient will remain. Many locations, especially the eastern
half of the county, have a greater than 1 in 2 chance of wind
gusts past 40 mph through the day.

The rest of the forecast looks quieter. A bit of lingering
moisture and cyclonic curvature could keep a few showers over
the area Wednesday, but most areas will remain dry. Otherwise,
it will be a close to normal spring day with temperatures near
to slightly below normal. Flow then turns more west to
southwest, and as a result we will see a return to above normal
temperatures across most of the area from Thursday through the
weekend as ridging builds across the Rockies. Wyoming will be
near the top of the ridge though, and this will lead to a couple
of shortwaves tracking across northern Wyoming and bring a
couple of chance of showers and thunderstorms on Thursday and
Friday. At this point though, no strong storms are expected and
most locations should remain dry on any given day.

The ridge axis should be over the area on Saturday, bringing a
warm and dry day to the area. After that, the ridge may break
down and bring a return of a more active pattern. At this point,
Sunday may have some thunderstorms, mainly in the west. The
middle of next week looks potentially interesting with an upper
level low approaching the area, but details this far out are
impossible to predict.

&&

.AVIATION /06Z TAFS THROUGH 06Z THURSDAY/...
Issued at 945 PM MDT Tue May 6 2025

VLIFR conditions will continue at KCPR through 18Z, quickly
improving to MVFR conditions. Light rain will be possible during
this time, but is expected to stay further east for the time
being.VFR conditions finally return by 20Z, as ceilings lift and
clouds begin to scatter out. Mostly clear skies will be possible
by then end of the TAF period.

MVFR ceilings at KRKS are expected to drop to LIFR by the start
of the forecast, as winds finally decrease, dropping to
VLIFR/LIFR after 08Z. These conditions will continue through
15Z, improving to MVFR. Clouds will continue to scatter out and
lift through the rest of the morning, with winds turning more
northerly through the afternoon.

KBPI, KPNA and KRIW could have light fog before 12Z and left
then mention of marginal MVFR vis in the forecast at this time.
Any vis restriction is expected to clear out no later than 16Z.

Otherwise, expected light winds (11 kt or less) for most
terminals through the TAF period, with clouds scattering and
clearing out through the afternoon into the evening.

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...Dziewaltowski
DISCUSSION...Hattings
AVIATION...LaVoie