756
FXUS65 KRIW 161020
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
420 AM MDT Thu Jul 16 2026

.KEY MESSAGES...

- A similar day today to yesterday with warm and humid
  conditions and a scattering of showers and thunderstorms.
  Heavy rain is possible with any storm and local flooding is
  possible.

- Most showers and storms will be across the western half of the
  area through Saturday, the becoming more widespread Sunday
  and into early next week with the threat of flash flooding
  continuing.

- Above normal temperatures will continue through the period
  with highs in the 80s and 90s, with some locations close to
  100 on Friday and Saturday.

&&

.DISCUSSION...
Issued at 203 AM MDT Thu Jul 16 2026

It is amazing how quickly things can change with the weather in
Wyoming. Just a couple days ago we were talking about record heat
and very dry conditions. Well, the weather has decided to do a
Freaky Friday on us and flip into full monsoon mode. We had some
reports of flooding today and the chance will be around through the
next several days.

Water vapor imagery shows a large plume of monsoonal moisture
continuing to stream northward from the Gulf of California and up
through the Great Basin and into the northern Rockies. We continue to
have some rain and some thunderstorms early this morning, especially
in the south which just happened to light up when the previous shift
left for the night. Luckily, the storms have some movement but there
have been some good local rains, Big Piney got a quarter of an inch
in only 20 minutes. The general trend is down tonight through and
most places should be rain free by sunrise. However, things look
similar to yesterday, with low level easterly upslope flow and
abnormally high precipitable water levels, as high as 200 percent of
normal. There is some steering flow but again, not a lot. So, it
looks almost like a repeat performance of yesterday with slow moving
showers and thunderstorms, although it could be a bit further east
that yesterday. Instability parameters are decent as well with up
to 1000 J/Kg of CAPE and lifted indices as low as minus 4. There is
not a lot of upper level forcing though so most storms should
largely be rain makers although you can`t rule out small hail or a
strong wind gust with any storm in Wyoming. With the local
flooding we had yesterday and a similar setup to Wednesday, we have
decided to issue a flood watch through midnight for the
Absarokas, Cody Foothills as well as Hot Springs County given
the favored low level easterly flow bringing upslope flow and
slow movement of the storms. Like yesterday, the most numerous
storms should end after sunset, but a few will linger after
midnight. Temperatures should be a few degrees cooler than
yesterday, but still above normal for this time of year.

I still feel there may be a bit less coverage on Friday and
Saturday, especially in central Wyoming. It still looks like
ridge may build a back to the west somewhat on these days. This
should decrease available moisture and instability somewhat,
especially in eastern portions of the area. However, it will be
going back to 150 to 175 percent of normal versus 200 percent,
so not a huge difference. The POPs reflect this fairly well
again, with the highest in the western mountains on each day.
And like the previous days, most should be diurnal but a few
showers could linger after midnight and possibly until sunrise
the next day. Temperatures will also warm a bit, especially East
of the Divide, with some of the warmer spots getting close to
the 100 degree mark once again.

Sunday still looks like the transition day when the monsoonal push
will begin to move eastward, bring a better chance of showers and
storms to areas East of the Divide and fewer storms across western
Wyoming. Precipitable waters remain high all the way through much of
next week as well, as high as 200 percent of climatological normals.
There are still differences in the guidance in regards to which day
will be the most active though, as is to be expected this far out.
However, all areas should have a decent chance of getting some
needed rain over the next several days. We just don`t want too much
at once. And unfortunately, that is a definite possibility as well.

&&

.AVIATION /12Z TAFS THROUGH 12Z FRIDAY/...
Issued at 415 AM MDT Thu Jul 16 2026

Largely VFR conditions are expected through the TAF period. Dry
conditions are expected until around 18Z when showers and
thunderstorms will again develop in and near the mountains and
move slowly to the east and northeast. Terminals West of the
Continental Divide will be the first to be impacted, with areas
East of the Divide largely after 23Z until around 06Z. The one
exception is in vicinity of KCPR where there is only around a 10
percent chance of a shower or thunderstorm so it was not
included in the TAF forecast. Brief MVFR to IFR conditions are
possible in the heavier showers or thunderstorms as well as wind
gusts over 40 knots. Most convection should end by 06Z but a few
showers and storms linger after midnight.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
Flood Watch through this evening for WYZ002-003-005-007.

&&

$$

DISCUSSION...Hattings
AVIATION...Hattings