723
FXUS65 KRIW 181100
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
500 AM MDT Sat May 18 2024

.KEY MESSAGES...

- Elevated to critical fire weather conditions are expected today
for much of central and southern Wyoming with humidity below 15
percent and wind gusts of 30 to 40.

- Elevated fire weather conditions continue on Sunday.

- A stronger system will arrive Monday, bringing cooler and
  wetter conditions through Tuesday. Snow is expected in the
  mountains.

&&

.DISCUSSION...
Issued at 457 AM MDT Sat May 18 2024

A dominant westerly flow will become reestablished over the area
today as yesterday`s shortwave departs. Temperatures will be a
little cooler behind the associated front that has pushed south this
morning, but still around 5 degrees above normal for most. It will
be another breezy day, though not nearly to the extent of Friday.
However, fire weather concerns will continue as humidity values
again drop into the teens. With an even drier airmass overhead,
humidity may approach 10 percent across central and southern basins
this afternoon. Wind will quickly wane with sunset.

The prevailing flow will become more southwesterly this evening as a
trough deepens to our west. This will help bring in some Pacific
moisture, and we may see a few showers across the area overnight and
through Sunday morning as a leading shortwave crosses the area. This
will be followed quickly by a stronger wave rotating through the
broad trough during the afternoon. Additional showers and
thunderstorms should develop through the evening as a weak cold
front pushes east. However, the majority of the area will remain
dry. With another robust pressure gradient setting up, wind will
increase again for Sunday; widespread gusts of 30 to 40 mph are
likely, especially across southern and central areas. This will also
bring another day of elevated to critical fire weather conditions,
though slightly higher dewpoints will keep humidity values a little
higher than Saturday.

On Monday and Tuesday the trough mentioned above is forecast to drop
south and impact the area with widespread cooler temperatures and
precipitation chances. There is still plenty of uncertainty with the
evolution of this system and of course with the amount of available
moisture, but there has been a notable upward trend with QPF
recently. With the associated low placement across Wyoming on
Tuesday, locations east of the Divide appear favored to pick up
the most precipitation as upsloping is enhanced. Accordingly,
the mountains here could see a decent snow event and may need
winter weather highlights.

Further ahead, guidance is favoring a continued active pattern with
the next wave arriving in the Wednesday to Thursday timeframe. The
forecast reflects this trend with generally cooler than normal
temperatures and daily precipitation chances across the area through
the end of next week.

&&

.AVIATION /06Z TAFS THROUGH 06Z SUNDAY/...
Issued at 845 PM MDT Fri May 17 2024

VFR conditions will prevail through the entirety of
the TAF period. Winds have weakened over the past few hours,
with breezy conditions lingering across some terminals to start
the period. Skies will continue to clear overnight, with some
high clouds over northern WY gradually decreasing by the
Saturday morning. Winds return Saturday afternoon across all
terminals but will be less impactful. Gusts will range from 20
to 30 knots through the afternoon/evening Saturday for the
majority of terminals. Light and variable winds return around
sunset and continue through the end of the period. Skies remain
mostly SKC for all terminals Saturday, with mid level clouds
developing by the end of the period.

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

&&

.FIRE WEATHER...
Issued at 457 AM MDT Sat May 18 2024

Another dry and windy day will return elevated to critical fire
weather conditions to most of central and southern Wyoming today.
Wind will not be quite as strong as on Friday, but gusts of 30 to 40
mph are still expected for most of the area. Humidity again will
drop below 15 percent for much of this area. Wind ticks up a bit
again on Sunday as the surface pressure gradient tightens. There
will be some isolated convection in the area as a shortwave pushes
through, but the majority of the area will remain dry; elevated fire
weather conditions will continue. Cooler and wetter conditions are
expected for Monday and Tuesday as a stronger system arrives.

&&

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

&&

$$

DISCUSSION...Myers
AVIATION...Dziewaltowski
FIRE WEATHER...Myers