281
FXUS65 KRIW 061043
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
443 AM MDT Sun Jul 6 2025

.KEY MESSAGES...

- Isolated showers and storms will be possible this afternoon.
  Wind gusts to 55 mph is the main hazard, with the additional
  hazard of small hail for storms over southern Natrona County.

- Warmer conditions and increasing chances for elevated fire
  weather from Monday to Wednesday.

- Very hot conditions with widespread 90s and some locations
  getting close to the triple digit mark on Tuesday and
  Wednesday.

- Thunderstorm chances return by Thursday.

&&

.DISCUSSION...
Issued at 120 AM MDT Sun Jul 6 2025

Isolated showers have gradually ended over eastern portions of the
CWA this morning. Mostly clear skies are in place elsewhere away
from this activity. There is a low chance (20%) for low clouds to
develop around Casper between 10Z-14Z. One of the aspects against
this will be sfc winds turning to the west-southwest after sunrise.
The passage of Saturday`s shortwave will mark the end of the latest
active weather pattern, as drier air moves into the region. Flat
ridging will be in place today, with the front from Saturday night
washing out through the day and keeping daytime temperatures similar
to Saturday. Conditions will be mostly dry across the area
today, with Casper being an exception once again. A shower
and/or thunderstorm looks possible between 22Z-01Z over southern
Natrona County, including the Casper area and Casper Mountain.
Wind gusts up to 55 mph and small hail would be the likely
threats. Isolated virga showers will also be possible over
southern portions of Sweetwater County, with wind gusts up to 55
mph also possible.

Otherwise, the focus will shift to fire weather for the first
half of this week, as an upper level ridge builds over the
region from a strengthening high center over the Four Corners.
Winds look to remain light through Wednesday with mostly dry
conditions. A weak, shallow back door cold front will push
through Natrona County and the Wind River and Bighorn Basins
after sunset Monday evening, turning winds easterly in its wake.
The front will stall and wash out by sunrise Tuesday morning.
The warming trend will continue Tuesday, with 90 degree
temperatures returning for areas east of the Divide as well as
across portions of Sweetwater County. Several locations east of
the Divide could reach 100 degrees Wednesday, including
Greybull, Worland, Thermopolis, Casper and Riverton. The GFS
extended MOS guidance is forecasting 100 degrees at Riverton and
Greybull.

The next chance for precipitation looks to occur Thursday, as a
trough digs southward from Canada over MT. The previously discussed
remnant low will speed up and reach the Cowboy State Thursday
morning and eventually get absorbed by the incoming trough. This
could result in isolated showers early Thursday morning. This trough
would lower temperatures a bit and cause the high to retreat further
south. Moisture return looks to be confined over northern portions
at this time, with Johnson County having the best chances for
precipitation. Additionally, strong northwest winds could hit
northern Johnson County, including Buffalo, in the wake of the cold
front associated with the trough. No strong wind signatures are
evident yet, but gusts of 50 to 60 mph could occur as this would be
common with these kinds of fronts. There could also be a
significant reduction in temperatures Friday morning as a result
of this front.

&&

.AVIATION /12Z TAFS THROUGH 12Z MONDAY/...
Issued at 437 AM MDT Sun Jul 6 2025

Largely VFR flight conditions are forecast the entirely of the
TAF period. Winds are expected to be around or less than 10kts
at all terminals after 09Z with mostly clear skies. Winds
increase between 19Z-20Z with KPNA, KBPI, and KRKS seeing gusts
around 20kts Sunday afternoon. There is a chance for
thunderstorms at KCPR beginning around 23Z on Sunday.
Thunderstorms are expected to be very scattered so confidence in
direct impacts is around 1 out of 4 so opted for a PROB30 group
at this time. We also added a PROB30 for Rock Springs after 22Z
with around a 1 out of 4 chance of a shower or thunderstorm. All
showers should end around 06Z tonight.


&&

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

&&

$$

DISCUSSION...LaVoie
AVIATION...Hattings