987
FXUS65 KRIW 151040
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
440 AM MDT Mon Jul 15 2024

.KEY MESSAGES...

- Warm but seasonable temperatures and unsettled weather to
  start the week.

- Widespread showers and thunderstorms develop this afternoon
  with strong gusty winds of 40+ mph possible at times.

- Seasonable temperatures and afternoon convection continue
  through the first half of the week.

- Uncertainty remains regarding the second half of the week,
  with either seasonable and unsettled weather continuing or
  warm and dry conditions returning.

&&

.DISCUSSION...
Issued at 244 AM MDT Mon Jul 15 2024

After multiple days of much above normal heat, temperatures will
begin to cool as we head into the start of the week. Highs today are
forecast to be in the low to upper 80s with warmer values near 90 in
parts of the Bighorn Basin. Sporadic showers and isolated
thunderstorms continue to move across the state this morning.
Showers and thunderstorms are expected to become more widespread by
the late morning and early afternoon.

The dominate potent area of high pressure that brought near to
record high temperatures to the Cowboy State will begin to subside
to start the week. This is largely due to a longwave trough digging
across the central CONUS, bringing with it an active northern stream
that aids in suppressing the high to the south. As a result of this
shift, westerly/northwesterly flow is expected to develop, which
will aid in funneling moist pacific air into the region. PWAT values
are forecast to be above normal with amounts ranging from 0.75 to
1.00 inches. This flow combined with daytime heating and Pacific
moisture will create widespread showers and thunderstorms this
afternoon and evening. The main concern with any convection today
will be strong gusty outflows and brief heavy downpours. Soundings
are showing a prominent inverted-V signature with dewpoint
depressions of 40 to 50 degrees in some places. This means that some
storms may be capable of producing outflow winds of 40 to 50+ mph.
While soundings are looking rather dry, PWAT values would indicate
that some storms will be capable of overcoming this dryness and
producing heavy downpours at times. The main limiting factor for any
convection this afternoon will be shear and CINH. Eastern parts of
the CWA look to have a more favorable environment, which may support
stronger storm development. Parts of Johnson and Natrona Counties
look to have the best chance of seeing stronger storms as shear and
instability will be more prevalent. This is shown with the Day 1 SPC
outlook which currently has a marginal risk for severe thunderstorms
this afternoon. Overall, showers and thunderstorms look likely this
afternoon with much of the CWA having a (20-50%) chance for showers.
Thunderstorms also look likely with most of the CWA seeing a (10-
40%) chance for thunderstorms. Showers and thunderstorms will
gradually dissipate by the evening with a few lingering showers
possible into the early morning Tuesday.

Due to the suppression of the high to the south and the development
of the potent northerly stream, unsettled weather is expected to
occur daily through the first half of the week. Pacific moisture
along with westerly/northwesterly flow will create daily chances for
afternoon showers and thunderstorms. The main concern with the
stronger storms remains the same, which is gusty outflows of 40+
mph. Temperatures will also remain around seasonable values with
highs in the 80s to low 90s. The second half of the week still has a
lot of uncertainty as models differ on the possible outcomes. The
key factor is the high to the south of our CWA, which will either
continue to funnel moisture into the region or amplify and move back
north. The scenarios differ slightly with the first keeping seasonal
temperatures through the week and daily chances for afternoon
showers and thunderstorms. The second scenario will have dry and hot
conditions return to the region with temperatures climbing back to
above normal values and reduced chances for afternoon
convection.

&&

.AVIATION /12Z TAFS THROUGH 12Z TUESDAY/...
Issued at 440 AM MDT Mon Jul 15 2024

Widely scattered showers continue over the forecast area this
morning, with an isolated lightning strike or two in a few
locations. This activity is expected to end by 15Z, before
showers and thunderstorms return across the area after 18Z. wind
gusts over 40 kt will be the main threat from these storms. MVFR
conditions could occur with some storms that produce brief
heavy rain. Convection will begin to end after 02Z, with any
remaining showers becoming isolated through 06Z.

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

&&

.FIRE WEATHER...
Issued at 121 PM MDT Sun Jul 14 2024

Warm but seasonable temperatures are expected through the first
half of the week. Widespread showers and thunderstorms are
expected this afternoon and evening with most seeing a (20-50%)
chance of precipitation. Strong outflow winds of 40+ mph may
occur with the stronger storms. Scattered afternoon showers and
thunderstorms will be possible daily through the first half of
the week. Increasing dew points and seasonable temperatures
through Wednesday will lead to higher relative humidity along
with improved overnight recovery.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...

&&

$$

DISCUSSION...Dziewaltowski
AVIATION...LaVoie
FIRE WEATHER...Dziewaltowski