629
FXUS65 KRIW 112237
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
437 PM MDT Thu Jul 11 2024

.KEY MESSAGES...

- Mid-summer near-record heat today through Sunday. Afternoon
  temperatures in the 90s to low 100s will be common.

- Isolated showers and thunderstorms will cause brief erratic
  wind gusts in the 45 to 60 mph range despite light winds
  outside of outflows.

- The air mass will be very dry over the next several days,
  leading to low relative humidities and increased fire weather
  danger.

&&

.DISCUSSION...
Issued at 255 PM MDT Thu Jul 11 2024

The big weather story for the region over the next several days
will be the mid-summer heat, with many locations in the 90s to
low 100s during the afternoons through Sunday. Heat Advisories
are in effect for locations east of the Divide where the heat
will be most notable; however, even locations west of the Divide
will be 10 to 15 degrees above normal. Take precautions if
outside to avoid heat-related illnesses. It`s not until Monday
that the presiding upper level ridge flattens slightly, leading
to a slight cooling. That being said, temperatures will still be
above normal next week, with highs in 90s for many.

Isolated afternoon and evening showers and thunderstorms will be
a concern due to the very dry air in place. These will be
relatively rare, with most locations staying dry over the next 4
days; however, locations that do have a stray shower or
thunderstorm move overhead are at high risk of experiencing 45
to 60 mph erratic outflow wind gusts. Some of these dry
microbursts in past days have damaged shingles and thrown
objects across fields. Assume strong wind gusts with any nearby
shower or thunderstorm.

Another weather concern will be elevated fire weather danger.
Fuels are quickly drying, and the mid-summer heat combined with
dry air will lead to low relative humidities. This is especially
pronounced overnight when usually RH recovers; however,
midslopes and much of the higher terrain above valleys and
basins will only see RH rise into the 35 to 50 percent range,
allowing any fires to burn more efficiently overnight. The one
mitigating factor is a lack of widespread wind, but afternoon
showers and thunderstorms may provide the aforementioned brief
strong winds, along with a small chance (10% or less) of dry
lightning.

No major change in the pattern is expected in the next week,
with mid-summer heat and isolated thunderstorms remaining in the
forecast through next week.

&&

.AVIATION /00Z TAFS THROUGH 00Z SATURDAY/...
Issued at 435 PM MDT Thu Jul 11 2024

With high pressure building to the west, hot and dry conditions
have developed over western and central Wyoming today. These
conditions will continue through Sunday, though there will be
periods of increased moisture and instability for isolated
showers and thunderstorms. This evening will see general VFR
conditions with some isolated showers and thunderstorms across
northern WY and into the Casper area. MVFR conditions are
slightly possible under the storms. More likely are stronger
outflow winds over 40 kts due to the convection. Otherwise,
winds will generally decrease overnight, though remain breezy at
a couple of sites.

Friday will be similar to Thursday with hot, dry and breezy
conditions. Winds will be breezy and gusty from the west-
northwest at most sites, with KCOD and KWRL seeing northerly
flow. Isolated showers and thunderstorms are again possible in
the afternoon, with KCOD having the highest probability of
impact.

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

&&

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

&&

$$

DISCUSSION...VandenBoogart
AVIATION...McDonald/LaVoie