985
FXUS65 KRIW 140857
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
257 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 /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 1055 PM MDT Mon May 13 2024

A couple of shortwaves will keep an active TAF period across the
area. In the short term, there will be some isolated convection
through the overnight hours moving from west to east. Western and
then northern terminals will have the best chance at brief impacts
through the morning. Conditions are expected to remain
predominantly VFR, though brief periods of MVFR ceilings are
possible with any storm that moves over terminals. The next wave
arrives by late morning and will set off another round of
showers and thunderstorms for Tuesday afternoon. All terminals
other than KRKS have at least brief mention of convection for
the afternoon. The main concern with this activity will be brief
MVFR ceilings and strong wind. There is some guidance hinting
at bringing this farther south to KRKS around 00Z Wednesday, but
confidence is not high enough to include this for now.

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...Straub
AVIATION...Myers