Casper, Wyoming 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

707
FXUS65 KRIW 091939
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
139 PM MDT Wed Jul 9 2025

.KEY MESSAGES...

- Near to record breaking heat is forecast across the state
  today with some locations likely to reach the century mark.

- Elevated to near critical fire weather conditions continue
  today with very low min RH values and periodic gusty winds.

- Virga showers and an isolated dry thunderstorm will be
  possible this afternoon and evening. Isolated gusts of 50 to
  60 mph cannot be ruled out nearby any developing showers or
  thunderstorms.

- Cooler temperatures arrive for Thursday with highs nearly 20
  degrees cooler compared to Wednesday in some locations by
  Friday.

&&

.UPDATE...
Issued at 138 PM MDT Wed Jul 9 2025

The upcoming forecast remains on track with little to no changes
from the overnight. Hot well above normal temperatures will prevail
across the state today. Highs are expected to near the century mark
in some locations east of the Divide with values in the upper 80s to
low 90s west of the Divide. There is the potential for a few
locations to see near or record high temperatures especially east of
the Divide. A remnant low will move across southern ID tonight which
will bring increased chances for showers and an isolated
thunderstorm or two. The best chances look to be across southern WY
with lesser chances elsewhere. The one thing to keep in mind will be
the overall dryness of the atmosphere which will likely hinder
precipitation from reaching the surface. So while it may look like
there will be chances for showers much of these showers will be in
the form of virga. Gusty outflow winds will be a concern as a result
of this dryness. The SPC has recently upgraded the day 1 outlook to
include a small area of marginal across far southern and northern
WY. The main concern as mentioned earlier will be gusty outflow
winds possibly ranging from 50 to 60 mph in isolated locations.
Showers continue through the overnight into the morning hours on
Thursday. Coverage will gradually spread east during this time with
most, likely not seeing precipitation reach the surface.

Thursday will see slightly cooler temperatures as a cold front
begins to near the area. This front will create some chances for
showers and thunderstorms during the afternoon and evening. Elevated
fire weather conditions continue across the state for Thursday but
are expected to gradually improve as moisture moves into the region
behind the front. A brief break from the heat is expected for Friday
as temperatures cool to below normal values. Highs are forecast to
be nearly 15 to 20 degrees cooler than Wednesday. Temperatures east
of the Divide will range in the mid to upper 70s with values in the
upper 70s to low 80s west of the Divide. Shower and thunderstorms
will be possible on Friday as the front passes with the best chances
remaining across central and northern WY. Elevated PWAT values do
look to possibly move into the region for Friday with well above
normal amounts mainly east of the Divide. This may create some heavy
downpours but these are expected to remain very isolated. The
weekend sees warmer and drier conditions return to the area with
highs returning to the upper 80s to low 90s. The next chance for
precipitation does not look to arrive until the start of next week
as a trough moves across the region.

&&

.DISCUSSION...
Issued at 157 AM MDT Wed Jul 9 2025

The anticipated hottest day of the week has finally arrived. The
ridge that has been in place since Monday will continue its eastward
shift eastward this morning over the Cowboy State. 700mb
temperatures will be slightly higher today, ranging between 16C to
19C. 90 degree temperatures will be widespread once again, with
portions of the Bighorn Basin approaching 100 degrees. Winds
continue to look marginal for any fire weather highlights, however
gusts over 25 mph will occur at times (between 21Z and 00Z) over
areas with critical fuels. The atmosphere should be capped for most
areas, however isolated virga showers will be possible again in the
afternoon into the evening. Sweetwater County continues to look the
most likely location at this time, due a lead shortwave that will
move over the county from northern UT. Chances for these showers
will begin to increase after 21Z and move out of the area through
06Z Thursday. Wind gusts of 55 to 60 mph will again be possible, due
to the inverted-V sounding profiles in place.

A remnant low will approach the area through the overnight hours
Wednesday night, as it moves over southern ID. The aforementioned
lead shortwave will be ahead of this system. Increasing chances for
showers and isolated thunderstorms will become possible over western
portions after 06Z. Lightning chances are low, due to a lack of
moisture that is reflected in CAPE values of 100-200 J/kg.  These
chances for precip quickly spread east of the Divide by 09Z,
heading to the east-northeast. Precipitation chances associated
with this wave will exit Johnson County after 15Z, with
additional showers possible over Johnson and Natrona counties
through the afternoon. Little to no rain is expected from this
activity today and Thursday, due to a lack of moisture.
Temperatures will be about 10 degrees cooler across the CWA
Thursday as a result of the passage of this remnant low lowering
heights and suppressing the Four Corners high to the south (the
high will retrograde over the Desert Southwest at the same
time). Fire weather conditions will remain elevated as well, but
critical RH values will be isolated and confined to Sweetwater
County.

As expected, the timing from the trough dropping south from Canada
has slowed down and now looks to reach the MT/WY border Friday
morning. Any precipitation looks to be confined to northern portions
through the day Friday. Highs in the 70s east of the Divide is still
in the forecast, while areas west of the Divide stay in the low to
middle 80s.

Dry conditions then return for the weekend, with seasonal
temperatures on Saturday and highs in the 90s return for areas east
of the Divide on Sunday. Showers and thunderstorms could be possible
over far northern portions Monday afternoon, as another trough
drops south from Canada/British Columbia.

&&

.AVIATION /18Z TAFS THROUGH 18Z THURSDAY/...
Issued at 1139 AM MDT Wed Jul 9 2025

VFR conditions continue over the entire TAF period. Cloud cover
will gradually increase through the afternoon and overnight as a
shortwave starts to push towards the region. Prior 00Z, mainly
virga showers with gusty outflow winds would be the main threat,
with very minimal (near zero) chances for precipitation. After that
time, there will be increased chances for showers and perhaps an
isolated thunderstorm, with most likely chances (30%) at KRKS
through around 08Z.

Skies remain BKN through most of the night with cigs generally above
FL150. Then, the initial push of a cold front will move north to
south through the region early Thursday morning. This will lead to
winds shifting to north or northeast for most terminals east of the
Divide. There is a slight chance (10%) of some showers with this
front, but not enough confidence to include mentions in the TAFs.
The main cold frontal push will come later in the day with stronger
northerly winds and more likely precipitation chances Thursday
night.

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

&&

.FIRE WEATHER...
Issued at 138 PM MDT Wed Jul 9 2025

Elevated to near critical fire weather conditions are expected
across much of the area today. Well above normal temperatures are
forecast for the state with min RH values ranging in the single
digits to low teens. Winds will be gusty at times this afternoon
with periodic gusts of 20 to 30 mph. Stronger gusts will be possible
with any nearby developing showers or thunderstorms. Isolated virga
showers and an isolated dry thunderstorm cannot be ruled out this
afternoon/evening especially across southern WY.

&&

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

&&

$$

UPDATE...Dziewaltowski
DISCUSSION...LaVoie
AVIATION...Hensley
FIRE WEATHER...Dziewaltowski