736
FXUS65 KRIW 030328
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
928 PM MDT Wed Jul 2 2025

.KEY MESSAGES...

- Lingering rain showers and thunderstorms will slowly taper off
  this evening ending around midnight.

- An influx of moisture will create chances for heavy downpours
  and localized flash flooding in poor drainage areas Thursday.

- Widespread afternoon shower and thunderstorm chances continue
  for the July 4th holiday with most likely chances (50 to 60%)
  across the northern half of the state.

- A drier pattern with near to above normal temperatures looks
  to return over the weekend and persist through the early part
  of next week.

&&

.UPDATE...
Issued at 222 PM MDT Wed Jul 2 2025

Showers and thunderstorms have continued to develop through the
early afternoon. Slow moving and training storms are a concern
today, as PWATs are much above normal. Some of this has already been
noted near Barnum in Johnson County and across portions of Park
County north of Meeteetse. Notably, there is enough low-level
dryness that Dual-Pol and other precipitation products are likely
overestimating QPE with these storms. Inverted-V soundings are
generally in place across the region, so gusty winds will generally
be the primary concern through the rest of the day. Showers and
thunderstorm chances diminish after about 2000L.

As noted in the discussion below, Thursday will see a much better
flux of moisture with PWATs nearing 1" or greater across portions of
the region. Flash flooding will certainly be a concern with training
storms and any storms that track across prone urban areas and local
poor drainage areas. Active and wet conditions will continue into
Friday, but July 4th is not looking like it will be a complete
washout, just scattered shower and thunderstorm chances in the
afternoon, mainly across northern WY.

&&

.DISCUSSION...
Issued at 223 AM MDT Wed Jul 2 2025

July started off hot and unsettled across the Cowboy State.
Temperatures reached the mid to upper 90s east of the Divide and mid
to upper 80s west of the Divide. Showers and thunderstorms developed
during the afternoon and evening with some locations seeing brief
downpours along with gusty outflow winds.

Wednesday will see much of the same with warm above normal
temperatures and afternoon showers and thunderstorms. The one
difference will be the start of an influx of well above normal
moisture. An upper level low over the western CONUS will begin to
funnel moisture into the region. Models show PWAT values of 0.60 to
0.90 inches which would be nearly 100 to 150% above normal.
Convection is expected to be more widespread as a result of this
moisture starting to move in. However, there will still be some
dryness lingering through the atmosphere. This dryness and lack of
dynamics will limit stronger thunderstorm development. The main
concern will be strong gusty outflow winds as a result of dewpoint
depressions ranging between 40 to 60 degrees. Portions of northern
and central WY look to have the best chances to see these gusty
winds. Showers and thunderstorms linger into the evening before
gradually dissipating by the early morning hours on Thursday.

Thursday will see the warm and unsettled pattern continue. However,
moisture is expected to increase further with PWATs nearing 1 inch
translating to almost 200% above normal values. This will increase
the chances for periods of heavy downpours as showers and
thunderstorms develop and move across the state during the afternoon
and evening. Storms will have potential to produce localized flash
flooding as a result of this increased influx of moisture. The other
concern that develops on Thursday will be increased chances for
strong thunderstorms. These increased chances are due to higher CAPE
values along with more favorable dynamics as a result of a shortwave
trough moving across the region. While still a few days out the best
chances for strong thunderstorms looks to be over central and
eastern WY.

Looking towards Friday the 4th of July, unsettled weather looks to
be possible. However, there is still some uncertainty regarding how
widespread the showers and thunderstorms may be. Temperatures will
cool slightly compared to earlier in the week, returning to near
seasonable values. Above normal PWATs linger which would create
another day with chances for heavy downpours. Models show another
shortwave move across the region with the track differing slightly
between models. Some show a more northerly track which would bring
favorable chances for showers and thunderstorms to northern WY.
Other models keep it farther south leading to move widespread shower
and thunderstorm chances. The good news is that convection is
expected to dissipate by sunset leading to drier conditions by the
time it gets dark. Overall, there does look to be a period of
unsettled weather for Friday afternoon and evening but to where the
best chances will be is still to be determined.

&&

.AVIATION /06Z TAFS THROUGH 06Z FRIDAY/...
Issued at 927 PM MDT Wed Jul 2 2025

Any lingering rain showers or isolated thunderstorms will quickly
taper off within an hour or two to begin the TAF period. More
isolated showers are possible near KJAC Thursday morning before
widespread showers and storms develop in the afternoon. Moisture
values will be increasing during the day Thursday, so there is a
better chance for reduced VIS from the heavier downpours. As such,
have dropped VIS to 5SM for the majority of the PROB30 groups.
Scattered rain showers and isolated storms will linger well into
Thursday evening.

It will be a bit gusty at KRKS and KRIW Thursday afternoon,
otherwise wind will be around 10 knots outside of outflows and
downdrafts. Overall downdrafts and outflows should not be as strong
Thursday afternoon as low-level moisture will limit temperature dew
point spreads. Cloud heights will be a few thousand feet lower due
to the increased moisture as well. There is the possibility that
denser cloud cover will develop Thursday morning and prevent
convective initiation until later in afternoon.

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

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

UPDATE...Hensley
DISCUSSION...Dziewaltowski
AVIATION...Rowe