Area Forecast Discussion
Issued by NWS Riverton, WY

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000
FXUS65 KRIW 230423
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
1023 PM MDT Fri Mar 22 2024

.KEY MESSAGES...

- Snow begins for western Wyoming mountains Saturday morning.
  Western valleys will see a light rain-snow mix during the day
  before switching to snow Saturday evening.

- Precipitation spreads east of the Continental Divide Sunday
  morning, with much colder temperatures and snow becoming
  widespread after daybreak Sunday. Snow ends west to east
  Sunday night.

- Starting early Sunday morning and lasting into the evening, a
  cold front will bring strong and gusty north winds to the
  Bighorn Basin, Johnson County, and locations along Muddy &
  Cottonwood Creeks west of Boysen Reservoir in northern Fremont
  County.

- Temperatures slowly warm into mid-week, with afternoon
  mountain snow showers continuing until the next weather system
  moves in Thursday.

&&

.DISCUSSION...
Issued at 231 PM MDT Fri Mar 22 2024

Low-amplitude ridging aloft will persist through the evening
today, leading to a quiet weather afternoon and evening, light
winds, and mild temperatures about 5 to 10 degrees above
seasonal normals.

Overnight into the day Saturday, the pattern will change as a
longwave trough pushes onto the West Coast. Moisture ahead of
this system will be orographically lifted leading to widespread
western Wyoming mountain snowfall. Winter Weather Advisories
have been issued to cover this hazard. Jackson Hole, Star
Valley, and other western Wyoming valleys may see occasional
showers throughout the day, with rain-snow mixed precipitation.
West of the Continental Divide, precipitation becomes more
ubiquitous after sunset, with precip type switching to all snow.

The broad trough moves eastward over the Intermountain West
Saturday night through the day Sunday. East of the Divide, cloud
cover thickens, and overnight rain showers switch to snowfall
for lower-elevations after sunrise. A strong cold front pushing
southward from Montana will cause temperatures to drop
throughout the day, with the unusual situation of early morning
having the highest temperatures for the calendar day. Total
snowfall varies from location-to-location, but 1 to 3 inches is
generally expected for most lower elevations, with 6 to 12 inch
amounts being common in the higher mountain ranges. Most
precipitation ends Sunday evening.

It`s worth noting that the strong cold front Sunday will cause
very windy conditions for the the Bighorn Basin, Johnson County,
and locations along Muddy & Cottonwood Creeks west of Boysen
Reservoir (in the northerly flow lee of the Owl Creek Range) in
northern Fremont County. High Wind Watches were considered, but
winds currently look to remain below High Wind thresholds,
while still being quite strong, gusting 45 to 55 mph throughout
the day.

On Monday and into the middle of the week, the region sits
under broad troughing, but without any shortwaves of note.
Scattered afternoon mountain snow showers are likely (70%
chance). This will lead to temperatures only slowly moderating,
and remain about 5 to 10 degrees below average on Tuesday. Near
normal conditions return on Wednesday. The next large weather
system looks to begin moving in Thursday into Friday.
Confidence is currently low on details for this system, so have
stuck with consensus model guidance for the forecast.

&&

.AVIATION /06Z TAFS THROUGH 06Z SUNDAY/...
Issued at 1020 PM MDT Fri Mar 22 2024

SCT-BKN FL150-200 clouds continue to stream across the Cowboy
State. LIFR clouds have developed over Johnson County and north
of KCOD in the last hour. These clouds are expected to surge
southward to KCOD between 06Z and 08Z and stay in place through
16Z. An area of showers will move over southwestern and central
portions from 06Z to 13Z this morning, with VCSH occurring over
KBPI/KPNA and spreading east of the Divide to KRIW/KLND and
eventually to KCPR. South to southwesterly winds will begin to
increase across southern portions into Natrona County through
the morning, spreading across much of the CWA through Saturday
afternoon. Gusts of 25 to 35 kt will occur in these areas during
this time. Isolated to scattered showers and thunderstorms will
be possible during the afternoon across areas west of the
Divide and the northern half of the Bighorn Basin. The speed of
these storms will be rather quick, so have left any mention of
VCTS out of any terminal forecast for now. Showers will continue
across the forecast area through the night, with the focus
shifting to the northwestern portion of the forecast area.

A strong cold front will push southward across areas east of the
Divide after 00Z. North to northwesterly winds will increase
over the Bighorn Basin and northern Johnson County toward the
end of the TAF period, with these winds spreading southward
through the night.

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 6 PM Saturday to 6 PM MDT Sunday
for WYZ001-002.
Winter Weather Advisory from 11 PM Tonight to 6 PM MDT Sunday
for WYZ012-014- 015-024.

&&

$$

DISCUSSION...VandenBoogart
AVIATION...LaVoie


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