957
FXUS65 KRIW 141647
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
1047 AM MDT Tue May 14 2024

.KEY MESSAGES...

- Showers and thunderstorms will develop across the state
  today. Stronger thunderstorms will produce locally gusty
  winds.

- Another round of showers will develop on Wednesday, but will
  be more isolated in nature.

- Drier for the latter half of the week, but showers will still
  be possible across the northern Wyoming mountain ranges each
  afternoon.

&&

.DISCUSSION...
Issued at 205 AM MDT Tue May 14 2024

More active day in store across most of Wyoming today, with
showers and thunderstorms. The first in a series of shortwaves
is currently racing east across northern WY, and is bringing
increasing showers and a few thunderstorms. Radar and satellite
trends have shown an increasing trend both in number and
intensity of showers across the Bighorn Basin, which correlates
well with convective models. Expect this activity to continue
east this morning, with shower and thunderstorms generally
north of a Pinedale to Riverton to Casper line. A trailing wave
hot on the heels of the first wave will sweep into northern WY
early this afternoon. The second wave will catch up with the
first wave, bringing even more shower and thunderstorm
enhancement. CAM models do have most of the activity with this
second wave across northern WY this afternoon and evening, but
isolated activity will sweep across southern WY right around
sunset. Latest soundings show continued inverted-V profile,
common for Wyoming, which indicates any storms would produce
locally gusty winds. With a jet streak wrapping around the
southern end of the trough, best downburst threat would be
across southern WY with any isolated thunderstorms. Most
activity will fade quickly near sunset with loss of daytime
heating, but some shower activity may continue across Natrona
County through around 06Z/15.

As the trough slowly moves east on Wednesday, broad northwest
flow returns in its wake. With modest moisture and trailing
instability, some shower activity should develop along the
higher elevations of the Absarokas/Winds/Bighorns during peak
daytime heating. Northwesterly flow will then take those showers
southeastward, keeping a 30-50% possibility for showers
reaching into greater Fremont, Natrona, and Johnson Counties.
This pattern continues again on Thursday, with showers focusing
again on the Bighorns and Absarokas again, but having a bit more
trouble detaching from the higher elevations.

Lower confidence currently on forecast into the weekend, as one
model shows larger trough sweeping in Friday with more showers,
while other model has weaker trough passage mainly to the
north over the weekend. Cluster analysis of ensembles leans well
toward the latter, with continued light shower development on
northern mountains, while the trough mainly moves to the north
over the weekend. In either scenario, considerable lower level
drying is noted, with low humidity Thursday through the weekend.
With systems approaching Friday and/or Saturday, gusty
southwest winds will ramp up again, especially for southern WY.
This would lead to elevated fire weather concerns especially for
the weekend.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 1028 AM MDT Tue May 14 2024

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

In and out MVFR ceilings at JAC damming across the valley, but
VFR at all other TAF sites. Gusty northwest to westerly winds up
to 18-25kts to start the period through peak heating. Increasing
storm chances on station between 20-01Z at all sites carrying
tempo during these times with the hit and miss nature of these
isolated thunderstorms. Outflow boundaries exceeding 40kts are
possible at RKS but confidence low dependent on the vicinity of
these aforementioned storms. After 01Z, storms and winds will
diminish into the overnight hours with improving skies by
Wednesday morning.

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

VFR conditions expected for all sites with breezy northwesterly
winds up to 15-25kts. Increasing thunderstorm activity after 21Z
as storms west of the Divide push east and expand in coverage.
Tempo groups carried for these times through 00-01Z before
weakening due to nearing sunset and capping of the environment.
Any severe weather activity looks to stay south with only
possible gustier outflow winds over 30kts possible. Otherwise,
quieter conditions after 01Z with diminished winds into the
overnight hours. Lingering light rain at CPR after 06Z with MVFR
ceilings likely IAW some of the LAMP/BUFKIT sounding data
(70-80%). Improving conditions for other locations with CPR to
follow into the next TAF cycle.

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...Lowe