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000
FXUS65 KRIW 170442
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
1042 PM MDT Tue Apr 16 2024

.KEY MESSAGES...

- A digging trough will bring cooler and wetter weather for the
  next few days.

- Steadiest snow from the associated shortwave will occur
  overnight tonight through late Wednesday afternoon, with snow
  ending Wednesday night.

- Behind the shortwave, the cooler weather sticks around through
  the early part of the weekend.

- High pressure looks to return late in the weekend and continue
  through at least the first part of next week.

&&

.DISCUSSION...
Issued at 256 PM MDT Tue Apr 16 2024

The much above normal temperatures of this past weekend are a thing
of the past, at least for now. A trough continues to dig southward
out of Canada, which will bring a cold front and precipitation (yes,
snow) with it. The leading shortwave will begin to push into WY
later this evening. With it, snow showers will begin across the
northwest mountains this afternoon, pushing into the Bighorns after
dark. Steadiest and heaviest snow will be across the aforementioned
mountain locations and will occur late tonight through the day
Wednesday. Snowfall accumulation forecasts have not changed
appreciably since the previous forecast. Amounts are generally
around 6 to 10 inches across the northwest mountains including the
Tetons and Togwotee Pass areas with lesser amounts farther south.
Isolated higher amounts up to 12 to 18 inches are possible (40%
chance) across the northern peaks of the Absarokas, including around
the Beartooth Pass area. Highest amounts of 1 to 2 feet will occur
along the Bighorns.

Across lower elevations, snowfall amounts will be significantly
hindered by temperatures. Temperatures, which have been in the 50s
to near 60 this afternoon, will drop quickly after dark, and will be
below freezing by sunrise. Given the cold frontal passage overnight
and the dense cloud cover, temperatures will struggle to warm much
during the day Wednesday, so Precipitation may stay as snow (70%
chance of all snow) through much of the day across western Bighorn
Basin and Johnson County. However, it is mid-April, so snowfall
accumulation during the day will be limited, and roadways should
remain only wet during the day.

Across western portions of the Bighorn Basin, and lower elevations
of Natrona county, as well as across the Wind River Basin, any
precipitation during the day should fall as rain (70% chance of
rain), but will changeover to snow towards sunset Wednesday night,
as precipitation ends. Thus, any snowfall accumulations across those
areas will be limited (generally less than an inch).

The shortwave energy that is bringing the precipitation will exit
Wednesday night, and Thursday through Saturday will remain dry
behind the shortwave. However, the longwave trough will remain
stationary, and the colder air will remain with it. Temperatures
that were 10 to 15 degrees above normal over this past weekend will
now be 10 to 15 degrees below normal through Friday. A slight warm-
up will begin Saturday, but highs Saturday afternoon look to remain
5 to 10 degrees below normal east of the Divide.

A ridge looks to build to our west for the weekend, but not before
one last weak shortwave swings through the persistent trough. No
impacts look to occur with this shortwave at this time, save for a
few isolated to widely scattered snow showers across the western
mountains (enhanced by favorable NW flow patterns and orographics).
Then, as the ridge finally strengthens Sunday, temperatures look to
finally climb back to near normal and start to climb above normal to
start the next work week.

&&

.AVIATION /06Z TAFS THROUGH 06Z THURSDAY/...
Issued at 1041 PM MDT Tue Apr 16 2024

A strong cold front will push through the area from north to south
tonight into tomorrow. Wind has already shifted from westerly to
northeasterly at KCOD, with a drop to MVFR/IFR conditions expected
shortly as snow begins and low clouds develop. It may start as rain
briefly at KCOD before changing over to snow later tonight.
Rain/snow is expected to lag behind the cold front by a few hours,
so a noticeable wind shift (mainly from northwest to northeast) is
likely (80%) to occur before precipitation begins. Snow and low
clouds will drop KWRL to MVFR by 12Z/Wed and wind will stay
northwesterly through the TAF period. The cold front will continue
to slide south through the day on Wednesday with impacts beginning
at central terminals (KRIW/KLND/KCPR) late afternoon/early evening.
Conditions will predominantly drop to MVFR at these terminals as
snow/rain moves in, but IFR conditions are possible (30%) at times.

The best chance of snow showers and MVFR conditions at KJAC is from
14-21Z/Wed, otherwise showers should be limited to the mountains
around KJAC. Too low of a chance for prevailing rain/snow at
KBPI/KPNA/KRKS at this time. Mountain obscuration will be prevalent
once the cold front passes through each terminal. Wind will remain
breezy to windy, especially Wednesday afternoon.

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

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 6 AM MDT Thursday for WYZ001-002-
012.

Winter Storm Warning until 6 AM MDT Thursday for WYZ008-009.

&&

$$

DISCUSSION...Hensley
AVIATION...Rowe