288
FXUS65 KRIW 261722
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
1122 AM MDT Wed Jun 26 2024

.KEY MESSAGES...

- Shower and thunderstorm chances return to the area today.

- Stronger storms are expected Thursday with the best chances
  across northern, central, and southern Wyoming. Strong wind
  gusts and large hail are the primary threats.

- Cooler and drier Friday before a warmup begins this weekend. Not
  much chance of precipitation after Thursday until Sunday
  night/Monday.

&&

.DISCUSSION...
Issued at 404 AM MDT Wed Jun 26 2024

The hot and dry trend finally breaks down today with the arrival of
an embedded shortwave trough. This is evident on water vapor
satellite currently over western Idaho. This will shunt increased
Pacific moisture into the area. At the same time, decent Gulf
moisture will return from the east. Accordingly, showers and
thunderstorms will begin around sunrise across western Wyoming as
the shortwave arrives, moving northeast through the afternoon. With
PWAT values of 0.8-1.0 inches, any cell will have the ability to
produce brief, heavy rain. The other threat will be the usual strong
outflow winds up to around 40 mph this afternoon.

Most of this initial activity will move east of the area around 0Z.
However, with continued theta-e advection through the afternoon and
increasing upper-level forcing, another round of convection is
likely to kick off around this time. There is not great
consensus on coverage of storms from CAMs though, and for now
we have kept PoPs on the lower end for this evening. This may
need adjusted up if current trends hold. Otherwise, today will
be a little cooler with highs for most remaining below 90
degrees.

Stronger forcing arrives Thursday as a deeper and more pronounced
wave clips the area. Destabilization through the morning will make
for MLCAPE values of 500-1000 J/kg, and by early afternoon
convection will fire off across western Wyoming. This activity will
quickly move east through the afternoon, likely exiting most of the
area by 0Z. Some of these storms will be on the strong side, and the
SPC has recently expanded a marginal risk into much of northern,
central, and southern portions of the area. The greatest threats
will be strong wind and large hail.

Cooler air moves in within westerly flow behind the system for
Friday. This will make for highs in the 70s and low 80s for most, or
a few degrees above normal. There may be a few showers across
southern Wyoming and the northern mountains, but the majority of the
area will be dry.

Guidance favors a building ridge for Saturday and Sunday, returning
a warming and drying trend to the area. Sunday, in particular, looks
hot with highs returning to the upper 80s west of the Divide and
upper 90s east. With a drier airmass and gusty winds, elevated to
critical fire weather conditions are likely this weekend.

Further out, guidance is hinting at a stronger wave dropping south
from Montana Sunday night into Monday. This would bring the next
appreciable chance of rain to the area, with the best chances across
northern Wyoming.

&&

.AVIATION /18Z TAFS THROUGH 18Z THURSDAY/...
Issued at 1122 AM MDT Wed Jun 26 2024

Shower and thunderstorm chances continue to spread eastward through
the afternoon. All sites have at least a 15% chance to see a shower
or thunderstorm today. Locations with closer to 30% chances have
TEMPO or PROB30 groups in the TAFs. Shower chances will persist
overnight, but will be less than 20% for all terminals (except KRKS)
after 03Z. KRKS has the best chance to see thunderstorms after 03Z.
Then, shower and thunderstorm chances increase again late in the
period. West to southwest winds also increase late Thursday morning
as a shortwave passes through the area.

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...Myers
AVIATION...Hensley