005
FXUS65 KRIW 131648
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
1048 AM MDT Mon May 13 2024

.KEY MESSAGES...

- Fast moving pattern bring multiple systems through the region
  this week. Multiple chances for showers and thunderstorms
  through midweek.

- Temperatures remain near normal across the state in the 60s.

- Ridging brings warmer conditions for the latter half of the
  week, but daily showers will remain a threat for higher
  elevations.

&&

.DISCUSSION...
Issued at 212 AM MDT Mon May 13 2024

Weather pattern will remain a little more active starting this
week, as westerly flow brings multiple rounds of spring
rainfall to western WY. First round arrives today On the leading
edge of a shortwave trough sweeping in from the northwest. This
first wave will focus most shower activity on the northern third
of the state and the western mountains, where the best
probability of measurable rainfall occurs. Some showers may
reach into Fremont and Natrona Counties this afternoon, but
overall activity there will be brief and light still.

Next shortwave follows quickly on its heels for Tuesday, which
is currently more amplified than the Monday wave. This will
bring some added lift and shear across the northern 2/3 of the
state, resulting in more numerous showers and thunderstorms.
With dry air remaining at the sfc, inverted-v profiles will
bring the threat for gusty winds with any of these
thunderstorms, starting Tuesday afternoon across the Bighorn
Basin and the western mountain ranges, then shifting southeast
across Fremont, Natrona, and Johnson Counties Tuesday evening.
Lower elevations of Lincoln, Sublette, and Sweetwater Counties
have a lower chance for showers, but the gusty wind threat
remains there as well.

Shortwave trough number three follows right behind just in time
for Wednesday afternoon. Models are differing enough on
placement of this trough that rainfall forecast confidence
begins to decrease at this point. The trough likely will remain
farther west, taking most midlevel energy with it. But there`s
enough moisture still in place east of the divide for the shower
possibility to continue during peak heating Wednesday afternoon.

Beyond this for the latter half of the week, models are all over
the place on trying to build some weak ridging across the Four
Corners. While there would be a lack of shortwaves across
western WY Thursday through Saturday, enough moisture and
daytime heating would still bring daytime showers and
thunderstorms along the higher elevations of western and
northern WY each afternoon.

&&

.AVIATION /18Z TAFS THROUGH 18Z TUESDAY/...
Issued at 1048 AM MDT Mon May 13 2024

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

A couple of shortwaves will slide through the region over the next
24 hours. These shortwaves will bring scattered rain showers and
isolated thunderstorms to northern/central portions of the area,
mainly this afternoon/evening. The chance remains too low (30%) for
prevailing -SHRA, so have VCSH for KBPI/KPNA/KRKS terminals. At KRKS
conditions will remain dry through the TAF period. Sustained wind
around 15 knots, with gusts to 25 knots will occur at KRKS/KPNA/KBPI
terminals through the afternoon hours today. Gusty erratic wind
likely (80%) with any showers/storms. Similar conditions expected on
Tuesday, but thunderstorms will be more scattered than isolated
Tuesday afternoon.

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

A couple of shortwaves will slide through the region over the next
24 hours. These shortwaves will bring scattered rain showers and
isolated thunderstorms to northern/central portions of the area,
mainly this afternoon/evening. The best chance of isolated
thunderstorms will be at KCOD/KWRL, so went with VCTS from 21Z-02Z
this afternoon for these terminals. An area of -SHRA to SHRA is
possible (50%) at KWRL early Tuesday morning. Wind will be 10-15
knots this afternoon. Gusty erratic wind likely (80%) with any
showers/storms. Similar conditions expected on Tuesday, but
thunderstorms will be more scattered than isolated Tuesday afternoon.

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...
None.

&&

$$

DISCUSSION...Straub
AVIATION...Rowe