418
FXUS65 KRIW 151932
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
132 PM MDT Sat Jun 15 2024

.KEY MESSAGES...

- Warm and windy weather continues into Saturday evening across most
of the region with an elevated fire weather risk for central basins.

- Isolated showers and thunderstorms will be possible over parts of
Natrona, Johnson, and eastern Sweetwater Counties this
afternoon/early evening.

- Unsettled and cooler weather to start next week. Temperatures 5-15
degrees below normal, with the chance for light snow in the higher
elevations of northern Wyoming.

&&

.DISCUSSION...
Issued at 131 PM MDT Sat Jun 15 2024

The morning started off unsettled, especially across parts of the
Wind River Basin, where showers created outflow gusts of 50+ mph in
places such as Lander. Fortunately, the unsettled weather has passed
for much of the CWA, with the sun breaking through the clouds and
temperatures continuing to warm.

A shortwave is currently making its way across western Montana this
afternoon and will gradually move into Canada by Sunday. This will
leave much of the CWA dry, with most of the precipitation remaining
to the north. However, there is a small chance (10-20%) of an
isolated shower or thunderstorm developing in parts of Natrona and
Johnson County this afternoon/evening. The main impacts on our CWA
from this shortwave look to be increasing wind. The pressure
gradient has tightened and SW/W winds have gradual increased.
Sustained winds of 15-25 knots will be widespread today with gusts
of 30-40 knots at times. These winds combined with dry RH values of
10-15% will create elevated fire weather conditions during the
afternoon and evening today. However, fuels are still non-critical,
so overall fire concerns are expected to remain minimal for now.
Winds decrease after sunset becoming light and variable through late
Sunday morning.

After a stretch of above normal warmth, cooler weather will make its
return for the start of next week. This change in weather is largely
due to a potent upper-level low moving into the PACNW on Sunday.
Quiet weather and seasonable temperatures remain over the CWA for
Sunday, with breezy winds being the only thing of note. As the
system nears the region on Monday, winds increase and chances for
showers develop mainly across the northern CWA. This system ushers
in some very unseasonably cool temperatures, with 700 mb
temperatures ranging from -2 to -6 Celsius on Monday and Tuesday.
Believe it or not, this creates the possibility for light snow in
the higher elevations of the Tetons, Absarokas, Bighorns and YNP.
However, snow impacts are looking very limited with only light
accumulations possible in the highest elevations. Temperatures will
likely have a greater impact than any light snow that may fall
Monday and Tuesday. Models show a (40-80%) chance of seeing lows 32
degrees or cooler for many western basins and even a small chance of
(10-30%) in western Sweetwater County. Overall, low temperatures on
Tuesday and Wednesday morning are looking chilly. The current
forecast is showing lows to be 10-15 degrees below normal for much
of the CWA, with a good chance of the western valleys and basins
seeing below freezing values.

Quiet and warmer weather returns for the second half of next week as
an area of ridging tries building back into the region. Confidence
remains low at this time as some models are hinting at a few
disturbances trying to interrupt this flow. However, a return to
seasonable to above normal temperatures is looking likely at this
point.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 1122 AM MDT Sat Jun 15 2024

All terminals to be VFR through midday Sunday. The main aviation
concern will be gusty west to southwest surface wind of 15-35kts
that develops and becomes widespread between 18Z-21Z/Saturday in the
wake of an east-moving shortwave. These winds persist until around
sunset Saturday (02Z-03Z/Sunday) with lingering west to northwest
10-15kt winds for many areas until 06Z-09Z/Sunday. Otherwise, the
shortwave tracking across central Wyoming Saturday morning has
been producing pockets of showers and gusty outflow wind. The
tail end of this shortwave will be draped from around KCPR to
KRKS by mid-afternoon. Convection that forms along this boundary
in the vicinity of these terminals moves quickly to the
southeast by 23Z/Saturday. Remaining terminals are dry with no
impacts. There is a patch of mid-level moisture that will lower
mid-cloud decks overnight with a hint of embedded light showers
over northwest Wyoming. Again, no impacts with any weak
convection that may develop.

Please see the Aviation Weather Center and/or CWSU ZDV and ZLC for
the latest information on smoke, icing, and turbulence
forecasts.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

DISCUSSION...Dziewaltowski
AVIATION...Jones