297
FXUS65 KRIW 251159
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
559 AM MDT Tue Jun 25 2024

.KEY MESSAGES...

- Warm above normal temperatures are expected for today. Highs
  are expected to be cooler compared to the past few days but
  will still be 10-15 degrees above normal.

- Afternoon showers may create strong gusty outflow winds with little
  to no rain reaching the surface.

- Chances for precipitation and cooler temperatures look to
  arrive by Wednesday.

- Thursday may be the best day to see widespread showers and
  thunderstorms with much needed rain possible.

&&

.DISCUSSION...
Issued at 245 AM MDT Tue Jun 25 2024

Another hot day across the Cowboy State is in the books. Some
temperatures of note from yesterday, Lander hit 96, Riverton hit 95,
Greybull hit 102, Worland hit 99, and Casper hit 97. Unfortunately,
even with how above normal these values are there were no records
met or broken. Temperatures will begin to trend cooler starting
today, as high pressure is pushed out of the region by the end of
the week.

Warm and dry conditions persist for one more day. Highs today will
be in the low 90s east of the Divide and in the mid to upper 80s
west of the Divide. Winds will still be breezy at times but not to
the same degree as they were yesterday. Isolated showers are
possible during the afternoon mainly in parts of northern Park and
southern Sweetwater Counties. Due to the dry nature of the
atmosphere, most will see virga showers. The one concern is the
dryness of the atmosphere which may produce strong outflow winds
from these showers. An example of this was seen yesterday at Casper
airport, where an outflow created 60 mph wind gusts. While the same
degree of gusts are not expected today, they are still a possibility
during the afternoon and evening today.

As mentioned earlier, change is on the way, with cooler temperatures
and chances for precipitation for the second half of the week. The
change looks to really kickoff Wednesday, as a potent trough digs
across the PACNW. This trough will start to push out the area of
high pressure that has been influencing our weather over the past
few days. As the high pressure is ushered east, moisture rich air
will be funneled north just in time for the trough to start
providing favorable dynamics for shower and thunderstorm
development. The first real chance for precipitation will come
Wednesday afternoon and evening. Current guidance is showing a
minimum chance of precipitation ranging from (20-30%) across much of
the CWA. The one concern will be the ability of this moist air from
the south being able to mix throughout the atmosphere. CAM`s vary of
the degree of mixing, with some showing a deep dry layer near the
surface inhibiting precipitation from reaching the surface. Others
show a more mixed atmosphere, which would be favorable for shower
and thunderstorm development along with wetting rain on the surface.
If mixing is able to occur there is a chance of seeing some heavy
downpours with any showers or thunderstorms that end up developing.
This is due to the high PWAT values associated with this moist
southern air. Models are showing values of 0.75-1.00 inches with
splotches of 1+ inch. So overall for Wednesday there is still some
uncertainty regarding the exact impacts but the expectation should
be possible showers and thunderstorms during the afternoon and
evening.

Thursday looks to be the best day to see widespread precipitation
over the whole CWA. This is due to better dynamics as the trough
over the PACNW nears closer to the region. Another aspect is the
ability for moisture to mix throughout the atmosphere. Thursday has
the potential to be a very interesting day as the dynamics and
moisture is there for possible widespread thunderstorm development.
CAM`s are only just starting to reach this time frame, meaning we
will have a better idea of the convective environment within the
next day or so. As of right now it is looking like the CWA could see
widespread showers and thunderstorms develop during the day
Thursday. The main concerns from any convection would be strong
winds, small hail, frequent lightning and heavy downpours due to the
higher than normal PWAT values.

Temperatures look to cool behind the trough, as 700 MB temperatures
range from 1-7 degrees Friday into Saturday. Overnight temperatures
may be chilly in spots those nights, especially west of the Divide
where temperatures may flirt with the mid 30s. Overall, the heat and
dry conditions linger for another day before a change to cooler and
wetter weather. The weekend sees a brief return to warmer weather
with another chance of showers and thunderstorms for Sunday/Monday.

&&

.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 558 AM MDT Tue Jun 25 2024

VFR conditions will prevail through the period. West to
northwesterly wind gusts of 15 to 25 knots will occur at most
terminals this afternoon. Isolated virga showers are once again
expected this afternoon, most likely across southern Wyoming.
The main concern with this activity will be isolated outflow
winds gusting over 40 knots. Wind and any showers will subside
around sunset. An incoming wave will start spreading clouds and
a low chance of showers across western Wyoming near the end of
the period, but no impacts are expected at this time through 12Z
Wednesday.

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...
None.

&&

$$

DISCUSSION...Dziewaltowski
AVIATION...Myers