Area Forecast Discussion
Issued by NWS Riverton, WY

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000
FXUS65 KRIW 272313
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
513 PM MDT Wed Mar 27 2024

.KEY MESSAGES...

- Brief period of mild and quiet weather across the Cowboy State
  today with breezy conditions this afternoon.

- A quick but potent system arrives early Thursday morning with
  snow developing across western WY. Moderate to heavy snow
  falls across the western mountains Thursday morning.
  Temperatures may limit daytime accumulation in the western
  valleys.

- Sweetwater County likely sees a period of widespread
  precipitation Thursday afternoon and early evening. Isolated
  thunderstorms may occur.

- An active weather pattern is expected to develop for the end
  of the week into the Easter weekend. Uncertainty remains high
  regarding the exact impacts on the state Saturday through
  Monday.

&&

.DISCUSSION...
Issued at 212 PM MDT Wed Mar 27 2024

Mild and quiet weather returns for a brief period of time across the
Cowboy State today. Highs continue to moderate with values at or
slightly above normal. While a shortwave ridge is crossing the
state, enough moisture and instability exist for isolated snow
showers along and west of the Continental Divide. Winds increase
across the area this afternoon with most locations seeing breezy
conditions by the afternoon. Areas with favorable southwesterly flow
along the Wind Corridor will see the strongest gusts of 30 to 40
mph. Ridging is quickly ushered out of the region this evening as a
shortwave is ejected from a Pacific system off PACNW Coast. This
shortwave barrels across the Great Basin reaching western WY by
early Thursday morning.

Thursday starts what looks to be an active weather pattern that
continues through the weekend. The main contributor to this active
weather will be a large potent Pacific system that will eject
shortwaves through the end of the week and weekend. This system aids
in funneling Pacific moisture into the region. The first surge
arrives in Western WY early Thursday morning with snow developing as
W/SW flow becomes favorable for orographic enhancement. Jet dynamics
along with ample moisture create a quick punch of moderate to heavy
snowfall over western mountains Thursday morning into early
afternoon. Western valleys may see some mixing occur during the day
or limited accumulation due to strong March solar radiation. Snow
accumulations in the western mountains range from 3 to 8 inches with
local amounts greater than 12 inches in favored locales. Valley
accumulations should range from 1 to 3 inches. Winter Weather
Advisories are currently set to go into effect early Thursday
morning for YNP, and the Teton, Gros Ventre, and Wind River Ranges.
A Winter Weather Advisory has been issued for the Salt and Wyoming
Ranges due to an increase in QPF values today.

East of the Continental Divide remains mostly dry for the first half
of Thursday with the main concern being strong winds. Winds increase
Thursday across most of the state with gusts of 20 to 35 mph
possible at times. Southwesterly favored areas of the Wind Corridor
may see periods of 40 to 50 mph gusts with Red Canyon and Wyoming
Boulevard near Casper possibly seeing 55+ mph gusts. The afternoon
and evening on Thursday will see scattered showers (20-30%) develop
across areas east of the Divide as the trough axis passes through.
QPF continues to rise in Sweetwater County for the 6-hour period
from 3PM to 9PM Thursday. The HREF is showing a 40-70% chance of
seeing QPF amounts greater then 0.15 inches over central Sweetwater
County during this period. Depending on the timing of this,
precipitation could either fall as rain or snow with the potential
for snow along the I-80 corridor. There is also the possibility (10-
15%) for an isolated thunderstorm to develop during this time
period. The moisture and dynamics shift south overnight leaving
improved conditions for Friday. Temperatures are forecast to be
around normal values with most areas remaining dry. A few showers
are possible during the day (20-30%) mainly along the southern
border of WY.

The weekend continues to be difficult to forecast as there are many
different components. Currently models are in agreement on one
thing, which is a active end to March and start to April. However,
the exact locations, timing, and impacts remain highly uncertain.
The key components of this upcoming system to keep an eye on are
temperatures, development of lee cyclogenesis over CO, and the
amount of overspreading Pacific moisture. Weekend temperatures have
continued to trend cooler for much of the CWA. It may still prove
difficult for much snow accumulation during the daytime hours, but
Sunday night shows potential for accumulating low elevation snow
given upslope flow east of the Divide. There is rich Pacific
moisture which would aid snow production Sunday night depending upon
the location of a surface low in Colorado. Overall, there is the
potential for weekend travel impacts, especially Sunday evening into
early Monday morning.

&&

.AVIATION /00Z TAFS THROUGH 00Z THURSDAY/...
Issued at 512 PM MDT Wed Mar 27 2024

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

Other than an isolated snow shower until sunset, KJAC sees VFR
conditions until snow develops between 07Z-11Z/Thursday. Conditions
deteriorate at KJAC between 07Z-11Z/Thursday as Pacific moisture
arrives from the west with IFR prevailing by 15Z. The heaviest snow
continues until around 21Z/Thursday with MVFR prevailing after that
time. All other terminals remain VFR through at least 15Z/Thursday.
MVFR possible at KPNA and KBPI during the early afternoon before
spreading south to KRKS late in the period. Several high-resolution
models depicting the potential for heavier snow at KRKS late in the
period as a frontal band pushes through. Gusty westerly surface wind
diminishes between 01Z-02Z/Thursday, before steadily increasing from
the southwest late Thursday morning and early afternoon. Mountain
tops frequently obscured.

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

VFR prevails at all terminals through the forecast period. Wind will
be the primary aviation hazard. Gusty westerly surface wind 12-25kts
decreases during the evening hours at KRIW and KLND, while KCPR and
KCOD keep 10-18kt speeds much of the night. KCPR sees southwest wind
substantially increase to 25G35kts between 14Z-17Z/Thursday ahead of
an approaching weather system. Other terminals see west to southwest
wind 12-25kts increase between 18Z-21Z/Thursday, with the potential
for 30-35kts at KLND. Mountain tops occasionally obscured along the
Continental Divide.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 3 AM to 11 PM MDT Thursday for
WYZ001-012-014-015-024.

&&

$$

DISCUSSION...Dziewaltowski
AVIATION...Jones/Rowe


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