601
FXUS65 KRIW 162056
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
256 PM MDT Thu May 16 2024

.KEY MESSAGES...

- Elevated fire weather danger Friday afternoon and evening,
  with warm temperatures and wind gusts in the 40 to 50 mph
  range.

- Another windy day Sunday, with elevated fire weather concerns.

- An active weather pattern will be in place next week, with
  Thursday currently looking like the timeframe with the highest
  chances for widespread soaking rains and mountain snow.

&&

.DISCUSSION...
Issued at 250 PM MDT Thu May 16 2024

Westerly flow dominates across the region this afternoon and
evening, with temperatures about 10 degrees above average and
mostly clear skies, save for some high cirrus.

Friday will bring even warmer conditions about 15 degrees above
normal, along with elevated fire weather danger, as a weather
system moves across Montana and pushes a weak cold front across
Wyoming. Afternoon RH values will range from 10 to 20 percent,
with sustained westerly winds of 25 to 35 mph and widespread
gusts in the 40 to 50 mph range. Early afternoon through sunset
will be the period with the driest and windiest conditions.
Thankfully most areas are thoroughly in spring greenup, so fuels
are not a major concern at this time, keeping the threat of
impactful fires lower than it would be later in the summer. The
weak cold front will be mostly dry, so only isolated mountain-
based showers are likely as the front passes.

Saturday cools off a bit compared to Friday, but temperatures
remain about 5 degrees above normal, with dry conditions and
typical breezy conditions during the afternoon. Another weather
system approaches Wyoming on Sunday, tightening the pressure
gradient bringing a return of gusty afternoon winds. Relative
humidity will be in the 15 to 25 percent range, leading to a
repeat afternoon with elevated fire weather concerns. Only
scattered mountain-based precipitation is expected with this
system on Sunday.

On Monday, a reinforcing trough will bring colder air and
another chance (50% chance) for more widespread precipitation
east of the Continental Divide. Temperatures Monday cool to
about 10 degrees below seasonal normals. After a brief ridge
and drying trend mid-week, the active weather pattern continues
with a larger weather system poised to impact the region on
Thursday. This could bring another round of lower elevation
rain.

&&

.AVIATION /18Z TAFS THROUGH 18Z FRIDAY/...
Issued at 1111 AM MDT Thu May 16 2024

VFR conditions through the TAF period. Winds increase this
afternoon, with gusts 20 to 25 knots for many locations. Most of
these winds decrease by 03Z/Fri. Models are indicating downvalley,
northwest winds at KRIW this evening into the night, with winds
around 15 knots possible (60%-70%); models show this wind lasting
through 07Z to 10Z/Fri. A few showers are possible across the
northern Wyoming mountains this afternoon, but no impacts to
terminals expected (90%).

Friday is a windy day. Gusts begin to increase early morning,
increasing further for the afternoon (after the TAF period). Showers
are possible across the northern section of Wyoming, but at this
distance it is too difficult to pinpoint locations and timings.

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...VandenBoogart
AVIATION...Wittmann