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000
FXUS65 KRIW 170830
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
230 AM MDT Wed Apr 17 2024

.KEY MESSAGES...

- A digging trough will bring cooler and wetter weather today
  and Thursday.

- Steadiest snow from the associated storm will occur this
  morning through tonight, with snow ending after sunrise
  Thursday morning.

- Behind the storm, the cooler weather sticks around through the
  first part of the weekend.

- A warming trend begins Sunday and continue into the first half
  of next week.

&&

.DISCUSSION...
Issued at 214 AM MDT Wed Apr 17 2024

Mountain snow continues to fall over far northern portions this
morning with isolated rain showers over central portions and the
northern end of Star Valley. This is due to the diffluent flow ahead
of the Canadian storm system dropping southward this morning. The
overall storm track remains largely unchanged, with most of the
precipitation occurring over northern portions through the day and
gradually spreading southward into Natrona County and the Wind River
Basin later this afternoon. Any rain or rain/snow mix over northern
portions this morning will change over to snow between 10Z and 12Z.
Snowfall accumulations of 2 to 4 inches are expected for areas along
and west of Hwy 120 (Cody, Meeteetse, Clark) and along and west of I-
25 (Buffalo, Kaycee) today. However, these accumulations are
expected to stay in grassy areas due to the high sun angle in mid-
April. The one change with this forecast package is precipitation
amounts continue to trend downward. The moderate to heavy snow is
still expected to impact the Bighorn Mountains, but the 12"+ amounts
in the Absarokas will be confined to the eastern edges.
Additionally, much of any heavy snow over the far northern end of
the mountains is occurring now (0120 am) and snowfall rates will
decrease after sunrise this morning. A similar trend is also noted
for the Teton/Gros Ventres and YNP, where amounts up to 6 inches are
now expected. The associated cold front will reach the Continental
Divide later this morning a couple of hours after sunrise. The
resulting pressure gradient will cause west-northwest winds to
increase over southern portions of the CWA through the morning
hours. Gusts up to 35 mph will be widespread and impact areas such
as Big Piney/Pinedale, Rock Springs/Green River and Kemmerer by
midday.

As noted earlier, precipitation chances will increase over Natrona
County and the Wind River Basin this afternoon. Snow or a rain/snow
mix will occur and any snow that does fall will have difficulty
sticking on roads. The cold air arrives into these areas through the
evening, with freezing temperatures expected before midnight. North-
northwest winds will increase behind this push of cold air, with
gusts of 25 to 35 mph occurring across areas east of the Divide
tonight. Snowfall accumulations will be minor and highly variable,
ranging between 0.5 and 2 inches. Snow will end from north to south
through the night tonight, lingering over central portions and
gradually ending around sunrise Thursday morning. Winds will become
light by this time as well, with gusts up to 30 mph continuing over
northern Johnson County through the rest of the morning. Snow
showers will remain possible over the northern mountains Thursday,
with only a few inches of additional accumulation expected.

Mainly dry and cooler conditions will remain in place Friday, under
unstable northwesterly flow aloft as the storm system continues
eastward over the Great Lakes/Hudson Bay region. Snow showers will
remain possible over the northern mountains (20-30%), while winds
remain light across the CWA.

A warming trend begins Saturday, with slightly above normal
temperatures returning to some areas. Wind gusts up to 30 mph across
southern portions will coincide with these temperatures, as a weak
storm system passes to the north. Any precipitation chances will
remain confined to northern portions Sunday and Monday, as a result
of this system.

&&

.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...LaVoie
AVIATION...Rowe