951
FXUS65 KRIW 270445
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
1045 PM MDT Wed Jun 26 2024

.KEY MESSAGES...

- Showers and a few thunderstorms continue to bubble across the
  state. Some thunderstorms may contain gusty winds.

- A more widespread threat for stronger thunderstorms expected
  on Thursday for nearly all of the state. Western and Central
  WY will have the threat for very gusty winds and hail.

- Ridge builds back across the state for the weekend, with a
  return of much warmer and drier conditions. Gusty winds will
  increase the fire weather threat both Friday and Sunday.

&&

.DISCUSSION...
Issued at 202 PM MDT Wed Jun 26 2024

Shortwave continues to transit the state this afternoon, with
enough instability to spark a few showers. Main push has been
held back until current time due to building of daytime heating,
but more convective activity is setting up across central WY,
and another area developing quickly in NE ID. SPC did bring a
marginal sever threat into far NW WY this afternoon, with gusty
winds being the main threat. Any precip should be fairly light,
but a brief downpour may occur in stronger storms.

Thursday turns to a more potent day across the state as a
larger trough sweeps in off the PacNW Coast into the far
southern Canadian Prairies. Ahead of the trough, sfc moisture
will be building across the state, with dewpoint temperatures
starting the day in the 50s. Related PW values running 2 to 3
standard deviations above normal indicate plenty of fuel to
generate thunderstorms. Mostly clear morning skies will help
quickly destabilize this layer. As the trough sweeps to the east
during the day, diffluence ahead of the trough will bring good
lifting aloft, tapping the unstable sfc moisture layer. drier
air aloft will try to wrap in from behind during the afternoon,
trying to form a modest dryline-type boundary advancing across
the state. Storms would be able to tap the approaching 100 jet
to mix very gusty winds down to the sfc. Some hail is also a
threat, but this may be confined farther north closer to the
cold pool near the trough center. SPC already has marginal SVR
risk for nearly all of western and central WY, with slight risk
just to the east of the I-25 corridor. Main forecast issue is
where storms fire first. Initial showers may already form along
the WY/ID border midmorning, but the main building will
probably fire along the western mountains and quickly push east
during the afternoon, tapping the unstable sfc moisture. The
thunderstorm activity will be moving quickly, so most activity
should be well off to the east and southeast by early evening.

Friday will see the trough continue east into the Northern
Plains. Some lingering moisture and daytime heating may bring a
few showers along the higher elevations of the Bighorns, and for
southeastern Sweetwater County, but most other will see a nice
day with temperatures in the 70s and 80s. Friday will be windy
and drier, so some fire weather concerns may develop during the
afternoon. Saturday and Sunday will continue the warming and
drying trend, with temperatures back in the 90s. Sunday will see
gusty winds again in advance of the next trough sweeping into
the PacNW, so more fire weather concerns are noted here, as
gusts could approach 40 mph at times, while humidity levels fall
to near 10 percent.

Still watching with interest that next trough for late Sunday
and Monday. Current forecast does bring a good amount of Pac
moisture with it, but strongest lift occurs overnight, so peak
heating will be minimized as it passes.

&&

.AVIATION /06Z TAFS THROUGH 06Z FRIDAY/...
Issued at 1045 PM MDT Wed Jun 26 2024

Isolated rain showers and thunderstorms continue through the
overnight hours. Convective activity will end early Thursday morning
with clear skies paving the way for more convection Thursday
afternoon. A low pressure system will slide southeast into Wyoming
Thursday afternoon, which will lead to the development of scattered
rain showers and thunderstorms. Some of the thunderstorms will be
strong. As it stands right now KRKS has the best chance of
prevailing TSRA Thursday afternoon, but not a high enough chance to
add it to this issuance of the TAFs. There`s a slight chance (20-
30%) of thunderstorms at all terminals Thursday afternoon. Wind will
increase Thursday morning and continue into the afternoon. Wind
gusts of 20-30 knots will be prevalent across the area. Higher gusts
are likely (70%) with thunderstorm downdrafts/outflows. There will
be prevailing VFR conditions, with temporary drops to MVFR/IFR if a
thunderstorm moves directly over the terminal.

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