985
FXUS65 KRIW 120827
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
227 AM MDT Mon May 12 2025

.KEY MESSAGES...

- Temperatures will remain hot today, with highs in the 80s east
  of the Continental Divide. Some locations in the Bighorn
  Basin may flirt with 90 degrees.

- The hot temperatures and dry conditions will result in
  elevated fire weather conditions this afternoon.

- A strong Spring weather system will bring moderate to heavy
  precipitation to Wyoming beginning Tuesday afternoon and
  ending Thursday night. Rainfall amounts may exceed 1 inch for
  northern portions of the area.

- The weather system mid-week will bring temperatures back to
  normal behind a strong cold front Tuesday.

- The weather pattern will remain unsettled with general
  troughiness through this weekend. Another strong Spring
  weather system appears likely (70%) to impact western and
  central Wyoming this weekend.

&&

.DISCUSSION...
Issued at 107 AM MDT Mon May 12 2025

The ridge that has been bringing the hot/dry conditions to the area
will slowly be pushed east as a strong low continues to approach
from the west. This low will struggle to impose its will on the
ridge as the ridge is firmly entrenched across the region. This
weather system will retreat somewhat today as the ridge holds the
line against the formidable low. Drier air (PWAT`s of 0.3-0.4") will
move in as dry southwesterly flow increases. The lack of moisture or
meaningful lift will prevent much, if any, convection from
developing this afternoon. Model guidance shows there really won`t
be any instability this afternoon. The bigger weather concern is how
dry and windy it will be this afternoon. This will result in
elevated fire weather conditions and would most certainly be worse
than elevated if greenup were not occurring. RH values will drop
into the low teens and upper single digits for most of the area
Monday afternoon. Couple this with wind gusts of 30-40 mph and you
get a day that burning is strongly discouraged.

The low should still struggle to push into Wyoming on Tuesday as the
ridge just doesn`t want to leave. Unfortunately the ridge is in a
losing battle as the low finally pushes it east Tuesday afternoon
into Tuesday night, with rain beginning across northwest Wyoming
Tuesday afternoon. Rain will become widespread Tuesday night,
becoming heavy at times across northern Wyoming. Precipitation will
be persistent through Wednesday evening as the majority of the
weather system will pass through from Tuesday afternoon through
Wednesday evening. Some of the most favorable locations for heavy
rain and locally higher rainfall amounts than the current forecast
are the eastern slopes of the Absaroka Mountains, Cody Foothills,
and northwestern Johnson County. At elevations above 8000 ft
precipitation will fall as snow and northern mountains will receive
anywhere from a foot to two feet of snow with this weather system.

Precipitation will lighten up and become less widespread Wednesday
night, but light precipitation will continue through Thursday
evening before the weather system fully exits Thursday night. There
is concern for minor flooding in the aforementioned areas from
Tuesday afternoon through Wednesday afternoon where rain will be
heaviest. Beyond Thursday the weather pattern remains somewhat
unsettled with some weak shortwaves possible through the end of the
week, but temperatures will rebound a bit into the upper 60s east of
the Divide on Saturday. Early indications are that another potent
Spring weather system could impact the region late this weekend into
early next week. This does appear to be another wet system with
plenty of moisture at its disposal.

&&

.AVIATION /06Z TAFS THROUGH 06Z TUESDAY/...
Issued at 941 PM MDT Sun May 11 2025

The last few lingering showers dissipate the first few hours of
the period. VFR conditions are expected overnight and through
the day Monday. Winds begin to increase once again Monday
morning, with widespread gusts 25 to 35 knots through the
afternoon. No precipitation is expected Monday, though there
could be a few showers over far northwest Wyoming late in the
period, but no impacts are expected at KCOD or KJAC through the
end of the period.

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...
Winter Storm Watch from Tuesday evening through Wednesday
evening for WYZ002.

Winter Storm Watch from late Tuesday night through Wednesday
evening for WYZ008-009.

&&

$$

DISCUSSION...Rowe
AVIATION...Wittmann