711
FXUS65 KRIW 172141
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
341 PM MDT Tue Sep 17 2024

.KEY MESSAGES...

- Widely scattered rain showers and thunderstorms this morning
  west of the Divide that will spread east in the afternoon.

- A cold front pushes through west to east from late morning
  through mid afternoon with gusty west to northwest winds
  behind it. There is a small window for strong to severe storms
  this afternoon in the vicinity of Natrona County.

- Winds will remain gusty tonight, increasing after midnight off
  the east slopes of the central and northern mountains, as well
  as southern portions of Fremont and Natrona Counties. A High
  Wind Warning is likely for these areas though Wednesday
  morning.

- Cooler and seasonal temperatures for the rest of the week and
  into the weekend with dry conditions as well.

&&

.DISCUSSION...
Issued at 1008 AM MDT Tue Sep 17 2024

An active day of weather on tap today. Showers and isolated
thunderstorms are ongoing over far western portions of the CWA this
morning, with a few thunderstorms moving northward over Sweetwater
County. These look to be forming along the cold front that is
expected to progress eastward through the day today. The overall
pattern is a bit messy this morning, with the dominant features well-
defined later this afternoon into the evening. The overall forecast
remains unchanged: the showers over the far west will spread across
eastward through the morning as the upper low moves eastward over
eastern ID, while showers and thunderstorms develop over eastern
portions of Sweetwater County and Carbon County and push northward
into Natrona and Johnson counties this afternoon. There is a brief
time frame where the storms in the latter area become strong to
severe before moving out of the CWA and into UNR and CYS areas.
Strong to severe wind gusts will be the main threat, but hail up to
1" cannot be ruled out. Some showers and thunderstorms could occur
through the day across the central basins as well.

The focus of the precipitation will shift to western portions and
eventually northwestern portions after 00Z, as the upper low moves
over MT. A moist, upslope flow will occur on the backside of the low
keeping the showers going tonight. These showers will spread
eastward through the overnight hours and continue through the day
Wednesday, before gradually ending late Wednesday night. The
gradient will remain tight tonight and Wednesday, as the low bottoms
out over eastern MT. 700mb winds will increase through the night,
with 50 kt occurring by 09Z Wednesday over southern portions of
Fremont and Natrona counties, as well as the Cody Foothills. The NAM
is depicting 700mb temperatures warming along the east slopes of the
Absaroka Mountains, indicative of a downsloping signature. Will
upgrade the High Wind Watch to a Warning as a result, but will push
the timing forward. Winds will remain strong through the rest of the
day Wednesday, with gusts of 45 to 55 mph in these areas. Wind gusts
of 25 to 40 mph will be common across the rest of the forecast area.
Otherwise, temperatures will be seasonal to slightly below
normal in the wake of the cold front.

An induced ridge will develop over he Cowboy State Thursday, as
another closed low moves over central/southern CA. This will keep
conditions dry, temperatures seasonal and winds relatively
light. This low will track over the Four Corners Friday, while a
trough tracks over Canada. Neither of these features will have
a direct impact on the forecast area, but winds over the Wind
Corridor could be slightly stronger with gusts of 25-30 mph in
the afternoon. Dry and seasonal conditions will continue through
the rest of the weekend.

&&

.AVIATION /00Z TAFS THROUGH 00Z THURSDAY/...
Issued at 340 PM MDT Tue Sep 17 2024

VFR conditions to prevail for much of the TAF period at all
terminals. A potent cold front has moved through the state today.
The front has brought strong gusty winds and scattered showers and
thunderstorms. Precipitation chances will gradually diminish across
terminals east of the Divide during the evening. KJAC will likely
see prevailing precipitation through at least the early morning
hours Wednesday. Widespread gusts of 25 to 35 knots will
continue this evening. Stronger gusts of 40 or more knots will
be possible nearby any developing storms. Overnight winds are to
remain gusty especially east of the Divide at KLND and KCPR.
Periodic gusts exceeding 45 knots are possible at times. Winds
are expected to gradually diminish through the morning hours on
Wednesday. Another increase in winds is expected for the late
morning Wednesday into the early afternoon. All terminals will
likely see gusts of 20 to 30 knots during the day Wednesday.

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 1008 AM MDT Tue Sep 17 2024

Gusty winds of 30 to 40 mph will occur outside of showers and
thunderstorms across all, but northwestern portions this
afternoon. Stronger gusts of 50-60 mph will be possible, as
thunderstorms develop and move over portions of zones 280, 281
and 289 for a few hours this afternoon. Winds will remain gusty
tonight into Wednesday morning, especially over zones 276, 280,
286, 288 and 289. Wind gusts will approach 60 mph in these zones
late tonight into Wednesday morning, gradually decreasing and
spreading across areas east of the Divide with gusts of 45 to 55
mph. winds will be slightly lower at 25 to 35 mph across the
rest of the forecast area. RH values will stay above critical
thresholds this afternoon and Wednesday, but the winds will
remain the bigger threat.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
High Wind Warning from 3 AM to noon MDT Wednesday for WYZ003-
019-020.

&&

$$

DISCUSSION...LaVoie
AVIATION...Dziewaltowski
FIRE WEATHER...LaVoie