Casper, Wyoming 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

938
FXUS65 KRIW 112320
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
520 PM MDT Sat Apr 11 2026

.KEY MESSAGES...

- Scattered showers and thunderstorms are expected through this evening
  as they move from southwest to northeast across the area.
  Strong wind gusts of 40 to 60 mph are possible with this
  activity.

- Elevated to near critical fire weather conditions are expected
  through the afternoon across much of central Wyoming.

- Scattered showers and thunderstorms are again expected on
  Sunday, though less widespread with the best chances across
  western Wyoming. Elevated to near-critical fire weather
  conditions will continue for much of the area.

- The unsettled pattern will persist through next week, with
  mild afternoon temperatures and several chances for moisture.
  A late week system may return cold morning temperatures
  (15-25 degrees) to lower elevations.

&&

.UPDATE...
Issued at 1157 AM MDT Sat Apr 11 2026

Convection is beginning to increase across western and southern
Wyoming late this morning as a shortwave arrives ahead of an
approaching upper low. Continued diurnal heating will allow MLCAPE
values to build to 100-500 J/kg across the area, with showers and
thunderstorms expanding in coverage from west to east over the next
couple of hours. The main concern with this activity will be strong
outflow wind gusts given the relative dry, well-mixed boundary layer
(DLCAPE values of 500-1000 J/kg). This risk will extend through mid
evening, with the last storms expected to exit the area between 9 PM
and midnight.

&&

.DISCUSSION...
Issued at 145 AM MDT Sat Apr 11 2026

As an advancing trough makes it to northern California today,
southwest flow aloft increases across Wyoming, bringing better
moisture to the area. In addition, a trough in advance of the main
system passes through today. These factors combine to bring
increased precipitation chances today, with showers being able
to produce rain that reaches the ground. The main push of this
shortwave starts late this morning, with shower and thunderstorm
chances increasing from the southwest through the afternoon,
and then decreasing from the southwest to northeast between
about 6pm and midnight. Everywhere will have a chance for rain
today (snow levels around 9000 feet). The best chances will be
west of the Continental Divide, where the better moisture will
be. The current forecast depicts of blend of hi-res models, with
the reality being that it is nearly impossible to determine
exactly where a shower or storm could occur today, but they will
be around. Everywhere has at least a 20 percent chance, though
actual chances vary to be as high as 80 percent (mainly west of
the Divide). Many models seem to depict a cluster of rain
showers over Sweetwater County this afternoon, so confidence in
rain is better there. The main hazard with any showers or storms
would be outflow gusts, which could be up to about 60 mph.

The other hazard today will be wind, and some fire weather concerns
with it. Moisture does increase today, especially west of the
Divide, but minimum humidity values around 20 percent are likely for
basins east of the Divide, driest for Johnson County. It is also
going to be windy today, a result of a tightening pressure gradient.
Gusts 25 to 40 mph will be common, and for these drier places, near
critical fire weather conditions could occur.

For Sunday, precipitation chances remain (though much more limited
compared to today), mostly along and west of the Divide, though some
"spill-over" is likely. Current projected positioning of the
incoming low would favor the western mountains (i.e. Absarokas,
Tetons, Yellowstone) the most. Gusty southwest winds 25 to 40 mph
continue during the day as well, so elevated to near critical fire
weather conditions remain a concern.

For Monday and Tuesday, the model trend continues to be for a weaker
and drier system, unfortunate news for those wishing for
precipitation. Liquid totals have dropped once again, with very
limited chances for low elevation basin locations. Elevated to near
critical fire weather looks to continue as well as gusty winds occur.

Looking further ahead, there is growing confidence in a colder system
towards the end of next week (Thursday-Saturday). This system has
the potential to bring morning low temperatures in the low 20s, with
multiple mornings in a row under 30 degrees. This is a heads up to
those with sprinklers or vulnerable vegetation.

&&

.AVIATION /00Z TAFS THROUGH 00Z MONDAY/...
Issued at 519 PM MDT Sat Apr 11 2026

Showers and isolated thunderstorms are forecast to come to an end
from southwest to northeast by 03Z. PROB30 groups reflect these
shower/thunderstorm chances due to low confidence in direct impacts
to any terminals. Gusty 40kt to 50kt winds are possible at any
terminal in or with nearby showers or thunderstorms. Isolated severe
gusts near 60 kts cannot be ruled out. MVFR conditions will be
possible in the heavier showers and thunderstorms with occasional
mountain obscurations. Dry conditions are expected overnight. There
exists shower potential Sunday afternoon at KJAC, KCOD, KPNA, and
KBPI.

There is a 10 to 20 percent chance of low, MVFR ceilings at all west
of the Divide terminals (KJAC, KRKS, KPNA, and KBPI) through roughly
07Z/08Z. Of those terminals, confidence is around 20 percent so
opted to put a SCT020 group at this time. Gusty winds outside of any
showers or thunderstorms are forecast to diminish at most terminals
by 04Z at the latest. The exception terminals are KCPR and KCOD. At
KCPR winds remain gusty the entire TAF period. At KCOD, there are
indications of gusty downsloping west winds off of the nearby
mountains through sunrise on Sunday.

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...
None.

&&

$$

UPDATE...Myers
DISCUSSION...Wittmann
AVIATION...Gerhardt