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000
FXUS65 KRIW 160851
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
251 AM MDT Tue Apr 16 2024

.KEY MESSAGES...

- Strong wind will occur over the Bighorn Basin and Johnson
  County this morning, decreasing through the afternoon.

- Precipitation returns to northwestern portions this evening,
  with any rain changing over to snow after sunset.
  Precipitation will spread across northern portions through the
  night, with rain changing over to snow in the lower
  elevations by sunrise Wednesday morning.

- The northern mountains will see the most snow through
  Thursday, with lower elevations seeing light accumulations at
  times. Wednesday night will be the best time for this to
  occur.

&&

.DISCUSSION...
Issued at 250 AM MDT Tue Apr 16 2024

Showers will gradually end this morning across the CWA, but will
linger over the northern half of the Bighorns through 13Z. North to
northwest wind gusts of 30 to 40 mph will be widespread this
morning, with stronger gusts of 45 mph occurring in the Bighorn
Basin. The High Wind Warning for Johnson County will begin at 09Z,
with gusts around 50 mph. Gusts around 60 mph are expected after
sunrise. Winds will decrease across the area through the day, as the
pressure gradient relaxes as the storm system from Monday
continues its track over the Central Plains. Apart from the
aforementioned wind, conditions will be dry today with cooler
temperatures across the northern half of the forecast area.

This respite will be brief this afternoon, before winds increase
again across all but eastern portions this evening. This will be in
response to an approaching Canadian system from the north.
Precipitation will return to far northwestern portions by 00Z, with
isolated showers possible over the western mountains and the central
basins. Showers will spread across northern portions through the
overnight hours, pushing southward along the associated cold front
through the Bighorn Basin and Johnson/Natrona counties between 06Z
and 12Z. Precipitation will start out as rain, changing over to snow
over far northern portions of the CWA like Cody and Buffalo by 12Z
Wednesday. Eastern portions of the Bighorn Basin look to remain dry,
due to a westerly downsloping flow off of the Absaroka Mountains.
Any snowfall accumulation in these areas will likely occur before
sunrise Wednesday morning. Snow will occur during the day, but
accumulations will be confined to grassy surfaces. Isolated showers
will be possible elsewhere across the forecast area through this
timeframe as well. Another trend from the 00Z model runs is lower
precipitation/snowfall amounts from this system. With that said,
warning amounts of snow are still forecasted for the Bighorns,
likely due to the continued upslope flow and left front quadrant
jet dynamics. Advisory amounts of snow look more likely for the
Absarokas, Yellowstone NP and the Tetons, although locally
higher warning amounts are expected over the northern end of the
Absarokas. Precipitation will become more focused over areas
east of the Divide Wednesday night, with the best chances
occurring over central portions of the CWA. This will be the
best chance for accumulating snow to occur in the lower
elevations. The rest of the forecast area will mainly be dry
during the day Wednesday, but westerly wind gusts up to 35 mph
will be widespread across southern portions during the
afternoon.

Precipitation will continue over these areas Thursday, as the
Cowboy State remains under the supporting jet of this storm
system. However, additional precipitation/snowfall amounts will
be very minor. Cool and unsettled weather will continue into
Friday, as unstable northwest flow aloft continues over the
forecast area. This will lead to chances for showers to continue
over the northern half of the the CWA and any accumulating snow
being confined to the Absaroka, Bighorn and the northern end of
the Wind River Mountains. Dry and warming conditions are likely
for the weekend.

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 949 PM MDT Mon Apr 15 2024

West of the Divide...KBPI/KJAC/KPNA/KRKS Terminals

A large low pressure system is spinning in the Central Plains right
now, with wraparound moisture bringing scattered rain/snow showers
to the area. Rain/snow chances are too low (<10%) for all terminals
over the TAF period, so no prevailing precipitation groups for now.
A strong cold front will approach late Tuesday evening, which will
bring better chances for rain/snow just beyond the period. A low VFR
cloud deck will hang around at KJAC tonight, but should lift/scatter
out by 14Z/Tues. Prevailing VFR conditions will continue at all
terminals for the next 24 hours. Breezy at KBPI/KPNA/KRKS tonight
with a decrease in wind early Tuesday morning before wind increase
again late Tuesday morning at all terminals. Mountain obscuration
will improve Tuesday morning.

East of the Divide...KCOD/KCPR/KLND/KRIW/KWRL Terminals

A large low pressure system is spinning in the Central Plains right
now, with wraparound moisture bringing scattered rain/snow showers
and isolated thunderstorms to the area through tonight. The only
terminal with prevailing rain showers and isolated thunderstorms is
KCPR. A TEMPO has been added for this evening until 07Z/Tues at KCPR
to account for MVFR conditions at times due to thunderstorms. Rain
showers linger at KCPR until 14Z/Tues. A cold front will move in
Tuesday evening, with light snow possible at KCOD by 02Z/Wed. Wind
will shift northerly after the frontal passage.

It will remain breezy to windy for most of tonight before a lull in
wind occurs early Tuesday morning. Then, wind will increase
again late Tuesday morning. The predominant wind direction will
be from the northwest at all terminals through Tuesday
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 from 11 PM this evening to 6 AM MDT
Thursday for WYZ001-002-012.

Winter Storm Warning from 11 PM this evening to 6 AM MDT
Thursday for WYZ008-009.

High Wind Warning until noon MDT today for WYZ010-011.

&&

$$

DISCUSSION...LaVoie
AVIATION...Rowe