626
FXUS65 KRIW 071712
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
1112 AM MDT Mon Jul 7 2025

.KEY MESSAGES...

- Warmer temperatures Monday through Wednesday with an
  increasing chance for elevated fire weather conditions due to
  low relative humidity and hot temperatures.

- Very hot conditions with widespread 90s and some locations
  getting close to the triple digit mark Tuesday and Wednesday.
  The lowest elevations of the Bighorn and Wind River Basins
  have a 30-50 percent chance of 100 degree highs Wednesday.

- A 20-40 percent chance of thunderstorms returns Friday
  afternoon and evening, especially along and east of the
  Continental Divide.

&&

.DISCUSSION...
Issued at 132 AM MDT Mon Jul 7 2025

Mostly dry conditions, light winds and mostly clear skies will
continue today. An upper level ridge will build over the region
through the day from a strengthening high center over the Four
Corners. Moisture will be confined along the I-25 corridor today,
with MLCAPE of 1500-2000 J/kg and a lifted index of minus 4 to minus
6. The tail end of a shortwave passing over the Northern Plains
could provide enough lift for a few showers and thunderstorms over
Johnson County this afternoon. Locally heavy rain will be the main
threat, as precipitable water values will be over 0.75" (which will
be near the 90th percentile) in addition to the previously mentioned
variables. Small hail could also occur as directional shear will be
quite strong (sfc easterly winds and 700mb westerly winds). The
mitigating factor here in this is the speeds will be quite weak
at 20 kt or so. A weak, shallow back door cold front associated
with the trough will push through Natrona County and the Wind
River and Bighorn Basins after sunset this 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. Isolated virga showers will be possible,mainly
over the central basins through the afternoon. Wind gusts of 55 to
60 mph will be possible from these showers, due to the large
dewpoint depressions. This convection does not look likely to repeat
itself on Wednesday, as the ridge begins to shift eastward over the
Cowboy State leading for the atmosphere to remain capped for most
areas. Several locations east of the Divide could reach 100 degrees
as a result of these capping inversions, including Greybull,
Worland, Thermopolis, Casper and Riverton. The GFS MOS guidance is
forecasting 100 degrees at Riverton, Worland and Greybull.

The next chance for precipitation looks to occur Thursday or Friday
afternoon. A remnant low will move over the Cowboy State Thursday
morning and exit over the NE Panhandle late in the afternoon. This
low could bring showers over southern portions. A trough will then
drop southward from Canada over MT Thursday night into Friday. This
could result in showers over northern portions Friday morning and
thunderstorms across areas east of the Divide during the afternoon.
This trough would lower temperatures 10 to 15 degrees for areas east
of the Divide and cause the Four Corners high to retreat further
south. 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. The cooler temperatures will be short-lived however, as high
pressure rebuilds over the area and readings return to the middle to
upper 80s on Saturday.

&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 1109 AM MDT Mon Jul 7 2025

VFR conditions through the next 24 hours with only FEW to SCT CU
at or above 10000 this afternoon. There are still small hints
for a shower trying to reach KCPR and KBYG this afternoon, but
any impacts will be minimal and brief between 21Z and 00Z. Winds
remain light overnight, and some west winds up to around 10kts
Tuesday morning.

&&

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

&&

$$

DISCUSSION...LaVoie
AVIATION...Straub