519
FXUS65 KRIW 101112
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
512 AM MDT Mon Jun 10 2024

.KEY MESSAGES...

- Isolated showers will remain possible this morning, with the
  focus shifting to Johnson/Natrona counties this afternoon. A
  strong to severe storm cannot be ruled out in this area.

- Warmer and drier conditions expected Tuesday and Wednesday,
  with a chance for showers and thunderstorms returning Thursday
  and Friday. Elevated river and stream levels will continue.

&&

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

Showers are beginning to end this morning (0130 am) as they move
toward the northeast. Thunderstorms have weakened and transitioned
to an area of showers over the Bighorn Basin. These showers are
expected to end in the next few hours.

The cause for this overnight convection is the shortwave trough that
has been discussed the last couple of days. It is currently over
western MT, trailing over eastern ID. This feature will continue to
progress eastward through the morning. As it does so, isolated
showers will be possible again over western portions of the CWA
after sunrise. The abundant moisture that was in place Sunday will
linger today, however sfc winds will turn more northwesterly through
the day as a result of the trough and associated cold front. These
features will push the Gulf moisture that was in place over Johnson
and Natrona counties further east over far eastern WY and western
SD/NE. As a result, the severe threat from thunderstorms this
afternoon will be confined along the front as it pushes southward
over Johnson County into northern Natrona County. Thunderstorms will
also be possible over southern portions of Sweetwater County, but
are not expected to be strong, let alone severe. Any other showers
and/or thunderstorms across the CWA will be very isolated (10%) this
afternoon. Otherwise, temperatures will be slightly cooler over the
forecast area today and 4 to 8 degrees cooler over western portions.
Additionally, gusty west-northwest winds will be widespread across
the forecast area, due to the resulting pressure gradient from the
passing trough.

Dry conditions will return Tuesday, as a transitory ridge moves over
the region. A more zonal flow pattern will be in place Wednesday,
but this will not stop temperatures from rising into the 90s across
areas east of the Divide. A strong high center over AZ/NM will
rebuild and push its ridge axis over the Northern Rockies Thursday
into Friday. Showers and thunderstorms could return to the area
during this time, as an upper level low from the Desert Southwest
surges northward. A longwave trough will build over the PACNW and
western Canada over the weekend, resulting in southwest flow aloft
over the Cowboy State. This could bring elevated fire weather
conditions to much of the CWA.

&&

.AVIATION /12Z TAFS THROUGH 12Z TUESDAY/...
Issued at 512 AM MDT Mon Jun 10 2024

A trough moves through the state today. All sites have at least a
10% chance of a shower or thunderstorm today. The best chances exist
east of the Divide, notably KCOD, KWRL, and KCPR, where
showers/storms will exist but comes down to if one actually impacts
a terminal; have PROB30 groups to cover these chances. At KJAC, some
showers may be moving eastward to start the TAF period. There is
about a 20% to 25% chance of KJAC seeing a shower move over the site
the first few hours of the TAF period. KBPI and KPNA have about a
15% chance of shower or storm through about 17Z/Mon, and KRKS has
about a 20% chance from roughly 19Z/Mon to 00Z/Tue. Gusty winds will
be the main threat from any showers or storms. The strongest storms
are favored near KCPR today.

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...LaVoie
AVIATION...Wittmann
HYDROLOGY...LaVoie