221
FXUS65 KRIW 042254
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
454 PM MDT Thu Jul 4 2024

.KEY MESSAGES...

- An unsettled weather pattern continues through this weekend as
  the trough hangs around.

- Isolated rain showers/thunderstorms continue across
  northeastern portions of the area from the Absaroka Mountains
  to Johnson County through this afternoon/evening. Elevated
  fire weather conditions persist across southern Wyoming today.

- A heat wave is looking more and more likely to begin next week
  as a strong ridge moves into the region. This appears to be a
  prolonged heat event, with highs 90+ F for most lower
  elevations beginning Wednesday.

&&

.DISCUSSION...
Issued at 224 PM MDT Thu Jul 4 2024

Troughing will be the general weather pattern through this weekend,
with several waves within the trough sliding through Wyoming. Today
(Independence Day/The 4th of July) looks pleasant temperature-wise
as cooler air remains in the area behind the weather system that
moved through yesterday. The cooler air aloft is allowing for
isolated convection to develop. The best chance will be along/near
the Absaroka Mountains/Bighorn Mountains where afternoon upslope
will contribute to lift. The threat of heavy rain has diminished
greatly today and it will be difficult for any locations to have
measurable rain.

Model guidance remains in disagreement on where the weak upper-
low/shortwave will be located as it passes by in northwest flow this
on Friday. The GFS still has it too far north and east for much of
any impact in the forecast area, whereas the ECMWF did shift further
north and east than yesterday`s solution, but still looks to clip
northeastern portions of the forecast area. The GFS has been more
consistent, so tend to believe it more in this situation. As such,
mostly clear skies on Friday will allow for temperatures to get back
to about normal (middle 70s F to low 80s F). Model guidance has
another wave coming down in northwest flow this weekend, which will
bring chances for isolated convection to mainly northeastern
portions of the area. The trend is for this wave to be slightly
stronger, with an increase in precip chances for northeastern
portions of the area as it slides through. This looks like the last
gasp for the trough that has been sitting over the region as a large
amplified ridge pushes into the western US early next week. This
ridge will bring hotter temperatures back to Wyoming and heat will
become the most impactful weather well into next week based on what
long-range model guidance is depicting. This looks like a prolonged
period of heat, so if heat is impactful to you then now is the time
to make preparations. Along with the heat comes very dry conditions,
which leads to fire weather concerns. This will be touched on in the
Fire Weather Discussion below.

&&

.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 454 PM MDT Thu Jul 4 2024

VFR conditions expected to prevail through the 00Z TAF period. Rain
showers and thunderstorms may cause brief reductions to MVFR
conditions due to lowered visibility at KCOD and KWRL. Gusty and
erratic winds are possible near thunderstorms and showers. Generally
light winds overnight, tapering off between 00Z and 03Z. More gusty
winds are expected Friday afternoon with mostly clear skies
across central and western Wyoming.

Please see the Aviation Weather Center and/or CWSU ZDV and ZLC for
the latest information on smoke, icing, and turbulence
forecasts.

&&

.FIRE WEATHER...
Issued at 224 PM MDT Thu Jul 4 2024

Elevated fire weather conditions will continue across southern fire
zones this week. The worst day will be Saturday as wind increases
ahead of the next weather system and RH will drop into the teens in
the afternoon. Isolated rain showers will pass through northern
zones today, but the CWR is very low. Smoke dispersal looks to be at
least good in the afternoon for the next few days at a minimum. As
temperatures increase next week it will become very dry. RH values
look like they will be in the low teens (possibly upper single
digits) for most lower elevations. High pressure will keep it dry,
with little to no chance of precip expected for most of next week,
at this time. The saving grace is wind will be much lighter than it
has been so far this summer thanks to the area of high pressure.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

DISCUSSION...Rowe
AVIATION...Gross/LaVoie
FIRE WEATHER...Rowe