182
FXUS65 KRIW 101955
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
155 PM MDT Mon Jun 10 2024

.KEY MESSAGES...

- Isolated showers and thunderstorms, some on the strong side,
  will continue through late afternoon. Strong outflow winds
  and isolated large hail is possible with this activity, as
  well as brief heavy rain.

- Warmer and drier conditions expected Tuesday through much of the
  week.

- Elevated river levels will continue this week.

&&

.DISCUSSION...
Issued at 153 PM MDT Mon Jun 10 2024

A strong shortwave visible on water vapor is currently pushing east
across northern Wyoming. This will be the impetus for convection
today, focused east of the Divide. An associated cold front will
drop south through the afternoon, shunting the deeper moisture that
was over the area yesterday farther to the east. There are a few
showers already ongoing across the Bighorn Basin late this morning,
and additional development is expected farther south and east over
the next couple of hours. The most favorable environment will be
across Johnson and Natrona counties where the better moisture will
be. With peak heating, instability will increase with MLCAPE values
of 500-1000+ J/kg and lapse rate of 7-8 C/km across these areas.
Given the well-mixed boundary layer, strong, gusty outflow winds are
the main concern, as well as isolated large hail with the stronger
storms. With PWAT values around three quarters to an inch, brief,
heavy rain is also possible. This activity will quickly move out by
late afternoon as the wave pushes farther east.

Tuesday will mark the beginning of a drier period as brief ridging
sets up across the region. Temperatures will peak 7 to 10 degrees
above average. Humidity will drop to below 20 percent across much of
central and southern Wyoming; with a breezy west wind, elevated fire
weather conditions will return for the afternoon. By Wednesday a
fairly zonal flow will take over, keeping active weather away from
the area. Temperatures will rise further, likely peaking in the
low to mid 90s for lower elevations east of the Divide. It will
be another windy day, meaning another day of elevated to near-
critical fire weather conditions.

By Thursday flow will become slightly more southwesterly, likely
helping to return isolated convection over the mountains. Guidance
diverges somewhat on Friday; the general trend is for increased
cyclonic flow with a better chance for more widespread convection.
Ensemble cluster guidance is still favoring troughing to increase
during the weekend.

&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 1140 AM MDT Mon Jun 10 2024

A cold front associated with a shortwave trough will pass through
the region today, and will bring a line of potentially strong
thunderstorms with it. KWRL and KCPR have the best chances of seeing
any impacts from this line of storms and thus have included a TEMPO
group to cover the most likely timing of those storms. Expect
locally heavy rain, gusty winds, and possibly small hail if a storm
passes directly over the terminal and brief MVFR conditions are
possible. Otherwise, VFR conditions are expected at all terminals
through the period. Breezy west to northwest winds at several
terminals will decrease between 00Z and 03Z and will be mostly light
through the rest of the period. Behind the line of storms, mostly
SKC conditions and light winds are expected through the rest of the
period.

Please see the Aviation Weather Center and/or CWSU ZDV and ZLC for
the latest information on smoke, icing, and turbulence
forecasts.

&&

.HYDROLOGY...
Issued at 212 AM MDT Mon Jun 10 2024

Rivers and creeks will continue to run high today at Action Stage or
below, but look to remain steady for now. SnoTel sites above 9000 ft
continue to drop with most sites dropping below 5 inches of SWE. The
remaining snow at these sites will likely be gone in the next day or
so. The notable exception is sites in the Tetons and portions of
Yellowstone NP, where 20-30 inches remain on the ground.

&&

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

&&

$$

DISCUSSION...Myers
AVIATION...Hensley
HYDROLOGY...LaVoie