575
FXUS65 KRIW 131915
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
115 PM MDT Tue Aug 13 2024

.KEY MESSAGES...

- Active weather continues today (Tuesday) and tomorrow
  (Wednesday) with showers and thunderstorms, most numerous
  West of the Divide. A few severe storms possible.

- Trending warmer and drier from Thursday into next weekend,
  with Saturday looking like the warmest and driest day.

&&

.DISCUSSION...
Issued at 112 PM MDT Tue Aug 13 2024

Marginal Risk (Level 1 of 5) remains in place across Wyoming for the
potential for severe thunderstorms this afternoon and evening.
Thunderstorm ingredients are starting to come together with
dewpoints in the upper 40s to 50s, SBCAPE values near 500 J/kg, and
bulk shear values 30 to 40 knots. The best combination of these
ingredients are along the western border and southwest corner of
Wyoming, so that will be the area to watch for the strongest storms
this afternoon. Elsewhere, the thunderstorms will likely be more
"garden-variety" or strong with small hail and strong wind gusts.
Cloud cover this morning has inhibited some storm development and
could lead to the storms overaLl being weaker today, like yesterday.
However, training storms, especially in areas that received a decent
amount of rainfall yesterday, may lead to localized flash flooding
in low-lying and poor drainage areas.

Wednesday there is another Marginal Risk (Level 1 of 5) across
central and southern Wyoming for the potential for storms to produce
strong to severe wind gusts and hail. While the better moisture,
instability, and shear will be outside of RIW`s forecast area,
dewpoints are still expected to be in the mid-to upper-40s with
SBCAPE 500-1000 J/kg and bulk shear values 30 to 40 knots. The
combination of these ingredients in best along the southern half of
the state, but a 30 to 50 percent chance of rain showers and
thunderstorms extends across the whole state.

Thursday brings drier and warmer conditions as a ridging pattern
takes back over through the weekend. Weak disturbances embedded in
the flow could kick off a few thunderstorms daily, but the
confidence is low in any widespread impacts. Thunderstorm chances
increase slightly Saturday night into Sunday as the ridge shifts
eastward, placing central and western Wyoming on the western side,
allowing some moisture to creep back in. Temperatures during this
time are expected to be in the 70s to 80s west of the divide and 80s
to low 90s east of the divide. Elevated fire weather concerns are
expected especially Friday and Saturday as minimum relative humidity
values approach critical across central and southern Wyoming with
southwest wind gusts 20 to 25 mph.

&&

.AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 1112 AM MDT Tue Aug 13 2024

Showers and thunderstorms this afternoon and evening. TAFs have
TEMPO groups to indicate where the best chances fall. Overall,
chances are 40% to 70% west of the Continental Divide, with around
40% chances or less east. Any storm could produce gusty outflow
winds 30 to 40 knots, with the potential for higher gusts in the
strongest storms. Brief drops to visibilities are possible too, if a
storm directly passes over a terminal. Chances continue through
about 06Z/Wed, mostly for locations east of the Divide.

Winds decrease this evening, with lessening clouds. Wednesday has
another chance of showers/storms near the end of the TAF period, but
especially after, for Wednesday afternoon.

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...

&&

$$

DISCUSSION...Gross
AVIATION...Wittmann