999
FXUS65 KRIW 100417
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
1017 PM MDT Sun Jun 9 2024

.KEY MESSAGES...

- Showers and thunderstorms will continue this afternoon and evening,
  most numerous across the northern half of the area. Strong
  wind gusts and brief, heavy rain are the main concerns with
  this activity.

- Monday will see continued isolated showers and thunderstorms.

- Warmer and drier conditions expected Tuesday through most of the
  week. Elevated river and stream levels will continue.

&&

.DISCUSSION...
Issued at 236 PM MDT Sun Jun 9 2024

Scattered showers and thunderstorms are ongoing across much of
Wyoming in response to the arrival of a shortwave trough riding
along the upper level ridge. This activity is expected to
expand eastward through the afternoon with the best coverage
across the northern half of the area. With both Pacific and Gulf
of Mexico moisture advecting into the area, there will be
fairly decent moisture available for convection (107% of normal
per 12Z sounding at RIW). Accordingly, instability will increase
through peak heating, with MLCAPE values generally peaking in
the 500-1000 J/kg range (with some caveats - such as the Bighorn
Basin which will miss out on deeper theta-e advection). The
best environment will be across eastern portions of the area
which will see MLCAPE rise to the 1000-1500 J/kg range. Given
the well-mixed boundary layer, strong, gusty winds are the main
concern, though large hail can`t be ruled out with any stronger
storms.

As the current convection wanes this evening, another shortwave will
push into western Wyoming. This will bring another round of showers and
thunderstorms overnight, most focused on northern and western
portions of the area. This round could bring a little more rain
accumulation, though this is very dependent on individual cell
locations. A quarter to half an inch is not out of the question from
any one cell, though most of the area will see much less. This
activity will wane by sunrise.

Monday will see additional showers and thunderstorms develop in the
afternoon as the next wave clips northern Wyoming. Accordingly, most
of the activity will be focused on areas east of the Divide. Strong
wind will be the primary concern again, with a lower hail threat as
well. Otherwise, an increased surface pressure gradient will make
for a gustier west to northwest wind for most of the area Monday
afternoon.

Further ahead, weak ridging to fairly zonal flow will take over.
Accordingly, warmer and drier conditions are favorable Tuesday
through at least Thursday. Ensemble cluster guidance is hinting at
increasing troughiness by the weekend.

&&

.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...
Issued at 1012 PM MDT Sun Jun 9 2024

VFR conditions to start the period for all TAF sites with mid
level ceilings across the CWA. Ongoing rain showers and a few
isolated thunderstorms exist to start the period that should
stay east of LND and pass CPR to its west and northwest.
Confidence low on any on station, so kept out of TAF completely.
Otherwise, some breezy winds will decrease behind these
aforementioned storms becoming less than 10kts through the late
morning. Expect winds to increase to 18-25kts for all TAF sites
after the 17-19Z time frame with daytime heating before
diminishing towards sunset around 01-03Z with nighttime
cooling. The only rain chances will be with JAC associated with
wrap around moisture from the ongoing trough with some off and
on light rain in the cooler air between 13-16Z. Otherwise, no
other weather elements for much of the period and into the next
several days.

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

&&

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

&&

$$

DISCUSSION...Myers
AVIATION...Lowe