470
FXUS65 KRIW 221730
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
1130 AM MDT Tue Apr 22 2025

.KEY MESSAGES...

- A quieter day across the state today with mostly sunny skies
  and seasonable temperatures. Isolated showers are possible
  across far northern WY this afternoon and evening. Gusty west
  winds will develop across southern WY this afternoon.

- Unsettled weather returns for Wednesday and Thursday with
  chances for widespread showers and isolated thunderstorms. A
  few strong storms cannot be ruled out from western WY into
  central WY late Wednesday. Precipitation then spreads east of
  the divide overnight into central and northern WY with decent
  mountain snow and lower-elevation rain through late Thursday.

- Seasonable conditions return for Friday into early Sunday with
  isolated showers each day. A stronger storm system is likely
  Sunday night through late Monday with widespread
  precipitation. Warmer and drier conditions return to the state
  by mid-week.

&&

.DISCUSSION...
Issued at 257 AM MDT Tue Apr 22 2025

A brief lull in the activity is expected across the Cowboy State
today with mostly dry and sunny conditions. The only exception to
this will be across far northern WY along the Absarokas and Bighorn
Ranges where some isolated showers are possible throughout the day.
Temperatures today will be seasonable with highs in the mid to upper
50s east of the Divide and upper 40s to low 50s west of the Divide.
A light breeze develops during the afternoon with stronger winds
across wind prone areas over portions of Sweetwater and Natrona
Counties. Clouds will begin to develop across western WY by the
evening as the next disturbance nears the area.

Wednesday will see unsettled weather return to the state as a
shortwave begins to dig across Idaho. Temperatures will be in the
low 50s west of the Divide and upper 50s to low 60s east of the
Divide. Showers and thunderstorms are expected to start developing
during the morning across western WY then spread east during the
afternoon and evening. Currently the best chance for thunderstorms
looks to be across western WY with much of the area seeing a (15-
30%) chance. There is a small chance that some of these storms could
become strong due to favorable dynamics across the region. Western
WY will be located in a area of PVA as the trough moves over Idaho.
Instability across the region will be marginal with values ranging
from 500-1000 J/kg as surface dewpoints will be in the 30s. The one
concern regarding CAPE values is the possibility this may be over
done, due to cloud cover that may linger and hinder daytime heating.
Other components such as shear and upper level flow look to be
present but not impressive. Overall, the dynamics are nothing
extreme or worth being overly concerned about. However, there does
look to be the potential for a strong storm or two to develop which
may produce small hail along with gusty winds. Locations east of the
Divide have the potential to see thunderstorms during the afternoon
and evening as well but currently chances look low. The best chances
will be over portions of southern Fremont and Natrona Counties. The
main limiting factor here looks to be moisture and low to mid level
lapse rates which will hinder storm development. Storms will
dissipate after sunset with showers continuing across the region
through the overnight.

The shortwave over Idaho will take its time moving east leading to
continued rounds of showers and possibly thunderstorms for much of
Thursday. Moisture is expected to be fairly limited so while chances
for showers will be widespread QPF values are forecast to be rather
low. Temperatures on Thursday will be on the cooler side with values
in the upper 40s to low 50s over central and northern WY. Due to
breaks in cloud cover temperatures over southern WY look to be
slightly warmer with values in the mid 50s to low 60s. These breaks
in cloud cover lead to more favorable conditions for thunderstorms,
which looks to be the reason for this part of the state having a 10-
20% chance of an isolated thunderstorm.

Unsettled weather persists for Friday as another disturbance moves
into the western CONUS, finally ushering the lingering shortwave
over Idaho to the east. Friday is currently forecast to be copy of
the previous days with chances for showers and thunderstorms. Daily
chances for showers and thunderstorms continue into the weekend as
the next disturbance begins to move east into the Great Basin. This
disturbance is starting to look rather intriguing, as models have
little idea as to what it will become. Some long range models show a
potent upper level low develop eventually bringing impacts to the
region for the end of the weekend. Other models show another
disturbance come from western Canada creating a mess over the
central CONUS and Rockies as the two disturbances interact. Overall,
the active unsettled weather is likely to persist through the
remainder of the week and possibly into the weekend.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 1130 AM MDT Tue Apr 22 2025

VFR conditions prevail through 18Z/Wednesday as zonal flow aloft
slowly backs to the southwest ahead of a longwave trough positioned
over the Intermountain West. Any showers Tuesday afternoon will
mainly be confined to the Absaroka Range and adjacent areas.
After 06Z/Wednesday, mid-level moisture increases in southwest
flow aloft and provides for the development of isolated showers
across the southwest by 12Z. Ceilings lower during the 09Z-
15Z/Wednesday timeframe, but remain VFR. Showers become a bit
more widespread by 18Z/Wednesday, especially across the west. A
few showers may sneak into central Wyoming, with the likely
result virga. Mountain tops above 11K feet MSL occasionally
obscured along and west of the Continental Divide after
10Z/Wednesday.

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

&&

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

&&

$$

DISCUSSION...Dziewaltowski
AVIATION...CNJ