139
FXUS65 KRIW 131721
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
1121 AM MDT Sat Jul 13 2024

.KEY MESSAGES...

- Another day of hot temperatures peaking in the 90 to 100
  degree range.

- Isolated showers and thunderstorms may bring strong outflow winds
  gusting 50 to 60 mph this afternoon and evening.

- Elevated to near-critical fire weather conditions are expected
  through the weekend.

- Smoke from western US wildfires will continue to move in to the
  area causing hazy skies at times.

- Temperatures remain hot through Sunday, then cool slightly for
  early next week.

&&

.DISCUSSION...
Issued at 421 AM MDT Sat Jul 13 2024

If you`re looking for relief from the heat...you won`t find it this
weekend. The strong area of high pressure that has been driving the
hot temperatures will persist, now centered over the Four Corners
area. Highs will again peak into the upper 90s to low 100s east of
the Continental Divide and lower to middle 90s west. That`s good for
around 10 degrees above normal for this time of year.

Similarly to previous days, there will be enough moisture and
divergence aloft rotating through the flow for some isolated
convection this afternoon. Hi-resolution models are showing perhaps
better coverage today, even across the southern half of the area.
However, we still expect the majority of the area to remain rain-
free given the very dry boundary layer and correspondingly high
LCLs. Accordingly, a lot of this activity will again be virga
showers. As we have seen repeatedly the last few days, this will
bring the threat of strong outflow winds gusting 50 to 60 mph.

The heat, low humidity, and outflow wind potential will continue the
heightened fire weather concerns today. On that note, we are
starting to see the annual pilgrimage of western US wildfire smoke
to the area. This trend is expected to continue through the weekend
considering that Wyoming is sitting at the 12 o`clock position of
the dominating anticyclone.

One difference for Sunday compared to today is that a stronger
shortwave will rotate through the flow, bringing increased
precipitation chances for the afternoon and evening as monsoonal
moisture expands over the area. With a slightly more moist lower
atmosphere, more rain will likely reach the ground Sunday. That said
- we are still not expecting a lot of rain with this wave, and the
majority of the area will again be dry and hot. Strong outflow wind
gusts will again be the primary concern Sunday.

By Monday it appears the ridge will get flattened somewhat, likely
providing a bit of relief from the heat as well as increased
rain chances. Further out, ensemble cluster guidance favors
continued anomalously high 500mb heights over the region as the
ridge builds back in through the end of next week. This would
keep temperatures on the warm side with precipitation chances
mainly limited to isolated diurnal convection.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 1121 AM MDT Sat Jul 13 2024

VFR conditions prevail through the period. Like the previous few
days, shower and thunderstorm chances occur this afternoon. They
will be isolated, so it is difficult to put confidence in the TAF;
have VCSH in a few locations where high-resolution models have more
consensus in showers, though even at those locations, low confidence
(about a 20% chance). The bigger impact from these isolated showers
will be gusty outflow winds. Gusts 40 to 50 knots are possible with
the stronger outflows.

Smoke continues to pass through the area. Currently, VFR conditions
are expected to remain, though some mountain obscuration continues.

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 421 AM MDT Sat Jul 13 2024

Elevated to near-critical fire weather conditions are again expected
today. Humidity will drop below 15 percent for the majority of the
area. Isolated showers and thunderstorms will continue to bring the
potential for strong outflow winds gusting 50 to 60 mph. Most of
this activity will be in the form of virga showers, but a wetting
rain is possible with a few of the stronger cells. Humidity recovery
will be a little better tonight, but still only reaching the 30 to
40 percent range along thermal belts.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
Heat Advisory until 10 PM MDT Sunday for WYZ004>006-010-011-
017-018-020.

&&

$$

DISCUSSION...Myers
AVIATION...Wittmann
FIRE WEATHER...VandenBoogart