Area Forecast Discussion
Issued by NWS Riverton, WY

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000
FXUS65 KRIW 222333
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
533 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 /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 530 PM MDT Fri Mar 22 2024

VFR conditions to start the period for all TAF sites, as winds
have diminish at KRKS and KBPI with scattered mid and upper
level clouds continuing. Expect increasing cloud coverage
overnight with VCSH expected after 06-07Z for sites west of the
Divide, as well as KRIW/KLND and KCPR. Best chances will shift
to northwestern portions between 12-18Z. 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.

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 midnight tonight to 6 PM MDT
Sunday for WYZ012-014-015-024.

&&

$$

DISCUSSION...VandenBoogart
AVIATION...LaVoie/Lowe


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