Casper, Wyoming 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

498
FXUS65 KRIW 071844
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
1244 PM MDT Sun Jun 7 2026

.KEY MESSAGES...

- Scattered showers and thunderstorms are expected this
  afternoon and evening, mainly along and east of the
  Continental Divide. Some storms could be strong with wind
  gusts of 60 to 70 mph and isolated large hail.

- Widespread elevated to critical fire weather conditions are
  expected through sunset given low humidity, gusty winds, and
  warm temperatures. This concern will continue through early
  this week as dry and windy conditions persist across the area.

&&

.UPDATE...
Issued at 1242 PM MDT Sun Jun 7 2026

Thunderstorm coverage is expected to increase over the next few
hours as instability builds. This will be focused mostly east
of the Divide where SBCAPE values will reach 500-1000 J/kg. The
strongest storms are still expected in the eastern Bighorn Basin
and across Johnson County where instability and shear (30-40
knots bulk) will be maximized. A narrower band of instability
should also develop farther south, extending through Sweetwater
County within a relatively more moist airmass. Stronger storms
today will be capable of occasional large hail and strong wind
gusts of 60 to 70 mph. Convection will wane by late evening,
with most of this activity to our east by midnight.

&&

.DISCUSSION...
Issued at 200 AM MDT Sun Jun 7 2026

WV imagery currently shows the deep upper level trough across
the Pacific northwest with the PFJ pushing cyclonically around
it with a positive tilt just to the west of the state. IR shows
the cooler cloud tops over eastern Idaho into central Montana
that will slowly push east into the CWA by Sunday morning
expanding throughout the day. Some light rain showers across
the west that will dissipate by sunrise with another round of
scattered thunderstorms expected to develop by late morning
across the Bighorn Basin. Gusty outflow winds expected with
this occurrence but severe weather is not expected through
early afternoon. As this pushes northeast by mid afternoon
~3-4PM, another area of development expected to off the leeward
side of the Absarokas by 4-5PM pushing across the north central
portions of the basin expanding to the Bighorns. These look to
form more of a line across the pre-frontal troughing with winds
again the main concern with possible severe thresholds being
met.

Attention turns to the more discrete cells come 6PM onward
towards sunset as the weak storms across Sweetwater County push
across Natrona into Johnson County. This will be when hail could
be more of a threat before quickly pushing northeast out of the
CWA before sunset around 8PM. With the ample surface convergence
and modest lapse rates, larger hail possible with moderate
confidence for severe thresholds up to a quarter. CAPE values
over 1500 J/kg ahead of FROPA will be conducive to this
occurrence with low level shear aiding in hail growth over 30
knots. The more upscale growth will occur after sunset and
northeast of the CWA into western South Dakota. These strong to
severe storms for hail potential will be short lived for our CWA
with the time frame of concern between 6-8PM. Otherwise, any
other stronger storms for the eastern Bighorn Basin across the
Bighorns and northern Natrona County will be more of a wind
threat but below severe thresholds at this point in time. A long
Sunday night looks to be in store severe wise for Rapid City and
point north and east into Monday morning.

Beyond the storm activity, expect FROPA to occur north to south
by late afternoon and into the late evening hours. Warm
temperatures ahead of the front will still give way to above
average temperatures but not record breaking as it was Saturday
due to the increased cloud coverage with this first shortwave.
Fire weather conditions expected to be near critical to critical
ahead of FROPA with gusty southwest winds to develop by mid to
late Sunday morning, strongest across Sweetwater to Natrona
Counties for the wind corridor up to 30 to 40 mph likely. Winds
shift with more of a northern component behind FROPA pushing
through the CWA after midnight and into early Monday morning
diminishing by sunrise.

Continued active pattern with the aforementioned L/W trough to
the northwest with a multitude of shortwaves through Thursday.
With cooler temperatures, severe weather is not expected but
expect a daily afternoon/evening dose of scattered storm
activity along with elevated fire weather danger as well. The
coolest day of the week looks to be Wednesday with a stronger
cold front with the the more widely scattered rainfall activity
expected. Beyond Thursday, the low finally exits to the east as
increased convergence aloft and upper level ridging builds back
in for Friday and into next weekend with a warming and dry
trend expected.

&&

.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 1107 AM MDT Sun Jun 7 2026

Winds are forecast to increase from the west to west-southwest at
all terminals by 20Z, with frequent gusts of 25kts to 35kts. Wind
gusts closer to 40kts are possible as well, especially at KCPR.
Winds will begin weakening between 02Z and 07Z Monday and becoming
more northwesterly to northerly during this timeframe behind a
Sunday afternoon cold front. Expect winds to be 12kts or less
overnight. Showers and thunderstorms are forecast to develop ahead
and along the aforementioned cold front. Shower and thunderstorm
coverage will be scattered by nature, so it was difficult to
pinpoint if a storm would directly hit a terminal. Thus, opt`d for
PROB30 groups for thunderstorms at all terminals expect KJAC this
afternoon and evening. A few thunderstorms could become severe in
the areas of or at KCPR, KRKS, KRIW, KLND, and KWRL, with 50kt
winds, large hail, and frequent lightning being the primary severe
threats. Confidence in any severe thunderstorms is highest at KCPR
and KWRL.

The shower and thunderstorm potential ends from west to east through
the afternoon and evening. There is a 30 percent chance of low
clouds moving into KCPR between 06Z and 14Z Monday, but did not have
enough confidence to go with MVFR ceilings. Another weak boundary
looks to trek across the state between 10Z and 16Z Monday, however,
confidence in this bringing any light rain is between 5% and 20% so
did not include in TAF at this time.

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

&&

.FIRE WEATHER...
Issued at 200 AM MDT Sun Jun 7 2026

Near critical to critical fire weather conditions expected for
Sunday afternoon and evening due to gusty southwest winds up to
30 to 40 mph and low relative humidity values down to 8 to 12%.
Although most fire weather zones are green for fuels (outside of
much of Natrona County), fire weather will be of concern for
Sunday. Scattered thunderstorms are expected from eastern
Bighorn Basin/Fremont County to Natrona/Johnson Counties for
late Sunday afternoon and early evening. Gusty outflow winds
possible up to 50-60 mph with some of the stronger storms.
Active weather pattern continues into much of the work week,
but with not as warm temperatures giving way to higher humidity
values and only elevated fire weather concerns after Sunday.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning until 8 PM MDT this evening for WYZ280.

&&

$$

UPDATE...Myers
DISCUSSION...Lowe
AVIATION...Gerhardt
FIRE WEATHER...Lowe