397
FXUS65 KRIW 080813
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
213 AM MDT Sat Jun 8 2024

.KEY MESSAGES...

- Isolated (10-20%) showers and thunderstorms will be possible
  this afternoon and evening.

- An area of subtropical moisture, along with Gulf moisture over
  eastern portions, will result in widespread showers and
  thunderstorms Sunday.

- Above normal temperatures through the next week will continue
  to melt any remaining snowcaps on higher elevations.

&&

.DISCUSSION...
Issued at 211 AM MDT Sat Jun 8 2024

The Cowboy State will once again be squeezed between an upper level
ridge to the west and an upper low/elongated trough to the north
over Canada. The ridge will have more of an influence over the
region, keeping temperatures about 10 degrees above normal. However,
these readings will be a few degrees cooler than Friday. West-
northwest wind will increase over areas west of the Divide this
afternoon as a result of this squeeze play, while areas east of the
Divide have a more northerly wind. Any convection will be very
isolated (10-20%), with the better chances over the Green
Mountains/Rattlesnake Range and southern Natrona County, the
Absaroka Mountains and far western portions. Strong gusty winds will
be the main threat from any shower and thunderstorm, as large
inverted-V soundings will be in place again. Winds will decrease
through the evening, with gusty outflows remaining possible east of
the Divide through much of the night.

The ridge will shift eastward over western portions of the CWA by
Sunday morning. This will allow an area of subtropical moisture to
move into this area by midday, leading to a more unstable
environment. A shortwave trough will also be moving onshore over the
PACNW Sunday morning. Rain showers and isolated thunderstorms will
be possible over far western portions before 12pm as a result.
Additionally, precipitable water values will range between 0.6 and
1.0 inches across the forecast area through the day. Gulf moisture
will advect into eastern portions through the afternoon, adding to
the moist and unstable atmosphere. This will culminate in CAPE
values of 1000 to 1500 J/kg and LI`s of minus 4 to minus 6 across
much of the CWA. SPC has outlined areas near the Star and Jackson
Valleys for Sunday, but would not be surprised to see this expanded
to areas east of the Divide. Strong gusty winds, small hail and
locally heavy rain will be the main threats as storms move toward
the east-northeast. This convective activity will be more isolated
after midnight, with showers remaining possible through the night
as the trough begins to move over western WY Monday morning.

Temperatures west of the Divide will be about 5 degrees cooler
Monday, with any convection staying over far northern portions of
the forecast area as the trough makes its way over MT. Gusty winds
will be more concentrated west of the Divide, due to the resulting
pressure gradient from the passing trough. Winds will also be more
north-northwesterly over the CWA.

Dry conditions will return Tuesday, as a transitory ridge moves over
the region. A more zonal flow pattern will be in place Wednesday,
before a ridge, from a strong high center over AZ/NM, rebuilds over
the Northern Rockies Thursday into Friday.

&&

.AVIATION /06Z TAFS THROUGH 06Z SUNDAY/...
Issued at 952 PM MDT Fri Jun 7 2024

VFR conditions expected throughout the period for all TAF sites.
Light winds and ample upper level moisture and clouds overnight.
Winds will increase to 18-25kts for most after around 18Z with
daytime heating and mixing to the surface. Mid to upper level
ceilings throughout the afternoon and into the evening hours as
winds diminish after around 01-03Z with sunset and radiational
cooling. No other weather elements are expected during the
period at this time.

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 207 AM MDT Sat Jun 8 2024

Rivers and creeks will remain on the high side today at Action Stage
or below, but look to remain steady for now. SnoTel sites above
9000 ft continue to drop and are now below 10 inches of SWE. At
this rate, the remaining snow at these sites could be gone in
the next couple of days. The notable exception is sites in the
Tetons and portions of Yellowstone NP, where 20-30 inches of
snow remain on the ground. Will keep the Flood Advisories in
effect as a result, likely continuing through the weekend.

&&

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

&&

$$

DISCUSSION...LaVoie
AVIATION...Lowe
HYDROLOGY...LaVoie