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000
FXUS65 KRIW 190719
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
119 AM MDT Fri Apr 19 2024

.KEY MESSAGES...

- Cool or most today, but temperatures warm Saturday, with above normal
  temperatures on Sunday.

- A weather system moves across northern Wyoming Sunday into
  Monday. Windy across western Wyoming, with precipitation
  chances for northern areas.

&&

.DISCUSSION...
Issued at 118 AM MDT Fri Apr 19 2024

Not much of a change today compared to yesterday. A strong low in
Canada, north of the Midwest, continues to bring northwest flow to
Wyoming. As a result, another day of weak instability develops
across the area. Snow showers begin developing late morning across
the central and northern mountains. Like yesterday, not much snow
expected, with only a 40% to 60% chance of more than half an inch
for the mountains, with about a 60% chance for more than an inch at
the highest peaks of the Absarokas, Winds, and Bighorn Mountains.
Outside these mountain locations, the area remains dry, with
afternoon cloud development due to the very slight instability (< 50
J/kg surface CAPE).

Temperatures today rise a little for the Sweetwater County area,
bringing the highs there near normal (mid 50s). Elsewhere, the
cooler air remains. Many lower elevation locations (not including
Sweetwater County) are forecast to be in the upper 30s to middle
40s. The Bighorn and Wind River Basins have a 70% to 80% chance to
see highs above 40, and a 10% to 20% chance to rise above 45; these
will be the warmest locations east of the Continental Divide.

A transitory ridge moves through the state starting Saturday. This
should help warm temperatures some, bringing most places around
normal. This drier air also keeps precipitation chances away, with
only isolated (15% or less) shower chances for the central
mountains.

The ridge axis crosses through for Sunday, with the warmest
temperatures for the next 5 days expected (90% confidence) this day.
High temperatures around the 70 degree mark look possible (40% to
60%) for much of the lower elevations. Jackson Hole will be notably
cooler, in the low to mid 50s. The aforementioned ridge is also
quick to move through on Sunday, with a trough moving through later
in the day. Precipitation chances increase from west to east through
the afternoon and evening, with chances mainly across the northern
half of the state. This system still does not look very impactful in
the precipitation department. However, wind may be another story.
The current NBM has mean wind gusts in the 30 to 40 mph range Sunday
afternoon for western Wyoming, and through the Wind Corridor to near
Casper. Will have to watch this system the next couple days to gain
better confidence in these winds.

Winds decrease for Monday, with lingering precipitation across
northern Wyoming. Temperatures also drop to around normal. As usual,
long range models begin to differ later in the period. Nothing
impactful stands out at this time, with some shortwave energy
occasionally passing through fairly zonal flow. A larger system
looks to approach around next Friday, but being about 8 days out,
would not put stock into any details.

&&

.AVIATION /06Z TAFS THROUGH 06Z SATURDAY/...
Issued at 1028 PM MDT Thu Apr 18 2024

Sites remain VFR this evening, with only a few sites holding
some midlevel cloud cover above 5000 feet. Any sites with cloud
cover will remain above this level overnight, with no fog
formation expected. Cloud cover will continue to fluctuate into
the day Friday, but remaining well above the VFR cutoff
level. Some isolated shower activity may develop along the
higher terrains during the afternoon, but are not expected to
impact local airports. Winds will remain light for all sites
through 00z/20, but some gusty northeast winds may kick up at
KCPR and KRKS beyond that into the overnight hours Friday
night/Saturday morning.

&&

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

&&

$$

DISCUSSION...Wittmann
AVIATION...Straub