579
FXUS65 KRIW 031955
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
155 PM MDT Wed Jul 3 2024

.KEY MESSAGES...

- An unsettled weather pattern continues through this week as a
  trough remains over Wyoming.

- Scattered rain showers and thunderstorms have developed across
  northern Wyoming this afternoon. Small hail and gusty wind is
  possible with these storms. Elevated fire weather conditions
  are occurring across southern Wyoming and will through this
  afternoon.

- The weather pattern favors breezy to windy conditions for the
  next 7 days and mostly dry conditions beyond Thursday. A heat
  wave is looking more likely to begin next week as a strong
  ridge moves into the region.

&&

.DISCUSSION...
Issued at 155 PM MDT Wed Jul 3 2024

Troughing will be the general weather pattern through this weekend,
with several waves within the trough sliding through Wyoming.
Independence Day (The 4th of July) looks pleasant temperature-wise
as cooler air moves into the area behind the weather system moving
through today. The current high temperature forecast is for upper
60s to middle 70s across the area.

The wave today has resulted in scattered rain showers and
thunderstorms across the northern half of the area. Who gets a good
wetting rain with these showers and storms will depend on where they
develop, but about from YNP eastward through the Bighorn Basin and
into Johnson County is likely to have measurable precipitation from
Wednesday through Thursday. Currently, the SPC has a Marginal risk
of severe weather in the Bighorn Basin eastward into Johnson County
for large hail and damaging wind, but this threat looks to be very
low based on how things have developed this afternoon. Still, it is
best to stay alert, especially in northern Johnson County where the
best chance of severe weather exists. Once the wave passes by on
Thursday the cooler air aloft will allow for isolated convection to
develop. The best chance will be along/near the Absaroka
Mountains/Bighorn Mountains where afternoon upslope will contribute
to lift. Localized heavy rain will be a threat on Thursday,
especially in or near the Bighorns as northwest flow sets up and may
lead to the formation of some training convection in the Bighorns.
PWAT`s don`t look excessive, so not expecting widespread flash
flooding.

Model guidance has diverged on the flow pattern for Friday. The GFS
shows northwest flow greatly weakening, whereas the ECMWF now has a
wave/weak upper-low clipping the area. Am leaning toward the FGS
solution which would more of a consistency forecast since models
have been showing weaker flow with that wave further north and east.
As such, mostly clear skies on Friday will allow for temperatures to
get back to about normal. Model guidance has another wave coming
down in northwest flow this weekend, which will bring low chances
for isolated convection to mainly northeastern portions of the area.
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.

&&

.AVIATION /18Z TAFS THROUGH 18Z THURSDAY/...
Issued at 1125 AM MDT Wed Jul 3 2024

VFR conditions expected to prevail through the 18Z TAF period
with the primary concern being strong winds and wind shifts with
the cold front passing through Wyoming today. Wind gusts 30 to
40 knots initially from the WNW, shifting NW and N as the front
passes through. The front is currently across northern Wyoming,
expected to drop south into central Wyoming over the next 3 to 6
hours. Rain showers and thunderstorms are expected along the
front as well, mainly impacting KCOD and potentially KWRL this
afternoon. Gusty and erratic winds are possible near
thunderstorms and showers.

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 155 PM MDT Wed Jul 3 2024

Elevated fire weather conditions will continue across southern fire
zones this week. The worst days will be today and Saturday as wind
increases ahead of weather systems and RH will drop into the teens
each afternoon. For northern zones wetting rain is possible (40-50%)
this afternoon/evening and even into Thursday for The Absarokas
Mountains/Bighorn Mountains. Lightning will be frequent with
thunderstorms on Wednesday and Thursday, but the storms should have
a good amount of moisture with them, so the chance of dry lightning
is low (<10%). Smoke dispersal looks to be at least good in the
afternoon for the next few days at least.

&&

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

&&

$$

DISCUSSION...Rowe
AVIATION...Gross
FIRE WEATHER...Rowe