546
FXUS65 KRIW 041029
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
429 AM MDT Fri Jul 4 2025

.KEY MESSAGES...

- An unsettled 4th of July with numerous chances for showers and
  thunderstorms; a few strong to severe storms possible in the
  afternoon.

- Chances for showers and thunderstorms continue into Saturday
  with a greater chance for severe storms developing especially
  across northern and eastern WY.

- Drier and warmer weather returns for Sunday into the first
  half of next week bringing increased chances for fire weather
  conditions.

&&

.DISCUSSION...
Issued at 227 AM MDT Fri Jul 4 2025

Its the United States` birthday today and turns 249, also known as
Independence Day or the 4th of July. The weather across the
Cowboy State is looking quite unsettled with chances for natural
fireworks occurring in the form of lightning and thunder.
Temperatures today will be on the cooler side but still around
seasonable values. Highs range from the low to mid 70s west of
the Divide and low 80s east of the Divide.

Two shortwaves will move across the region today, both are expected
to influence and aid in the development of shower and thunderstorms.
PWATs will remain above normal across the area but the main concern
as a result of this will be brief heavy downpours. Moisture has had
issues mixing down to the surface which has limited any flooding
concerns. So while flash flooding is not likely it cannot be
entirely ruled out. CAMs continue to show a couple rounds of showers
and thunderstorms today. The first moves into western WY by the mid
morning then gradually spreads into central and northern WY. The
next round follows shortly behind, developing by the early afternoon
with coverage being more widespread. There are some signs of a third
push developing in the late afternoon, lingering into the evening.
Another concern today will be the chance for a few isolated strong
to even severe storms developing. Instability is fairly limited but
a brief period of clearing should allow for CAPE to increase,
ranging from 700-1200 J/kg. Low to mid level lapse rates will be
fairly steep and favorable for some of these storms to become
severe. Other components such as bulk shear will be present with
values around 40 knots over parts of the area. The main hazards as a
result of these components will be strong gusty winds mixing down to
the surface as these storms move across the state. CAMs are showing
potentially widespread outflows of 40 to 50 mph with isolated gusts
possibly nearing 60 mph. Small hail will be possible if storms are
able to organize and enough instability develops. The best chances
for hail looks to be across western WY where some models show CAPE
values ranging from 1000 to 1500 J/kg. The potential for strong to
severe storms is also represented by the SPCs outlooks which has
placed much of WY in a Marginal risk for strong wind gusts and small
hail. Overall, today is not looking to be a washout but as mentioned
earlier it will be unsettled with chances for showers and some
strong to severe thunderstorm throughout the day.

The weekend is looking less active, but will still have some chances
for showers and thunderstorms. Coverage of these showers and
thunderstorms will be less widespread Saturday, with the best
chances being across central and northern WY. There is the potential
for some severe storms to develop Saturday as a result of the second
shortwave moving across Montana. The SPCs day 2 outlook highlights
this potential with parts of the state being placed in a Slight
risk. The areas of concern look to be across northern and eastern
WY, specifically the Bighorn Basin along with Johnson and Natrona
Counties. These areas will see instability develop during the day
and will be combined with favorable dynamics from the nearby
shortwave. The main hazards will be large hail and strong gusty
winds along with an isolated tornado or two.

The unsettled weather pattern finally looks to quiet down for
Sunday. Temperatures will be seasonable but begin to gradually warm
as ridging looks to start building in over the western CONUS. A
period of hot and dry conditions is beginning to look more likely
for the upcoming week. A big factor will be the strength of the
ridging and how long it can prevail over the region. There is still
time for things to change but as of right now the July heat and
dryness looks to be right around the corner. This may lead to some
elevated fire weather conditions so it will need to be monitored as
we head into the start of next week.

&&

.AVIATION /12Z TAFS THROUGH 12Z SATURDAY/...
Issued at 418 AM MDT Fri Jul 4 2025

Showers have primarily ended across the forecast area this
morning. An area of thunderstorms, currently over southeast ID,
will continue to move toward the northeast and could reach KJAC
between 12Z and 16Z.

This activity will be the precursor for the convective activity
expected later today, with multiple rounds of showers and
thunderstorms expected with movement from the west to east.
Thunderstorms will not be constant, hence the PROB30 groups, but
they should be a consideration at all airports between 18Z and
06Z. Lightning, heavy rain, and gusty outflow winds will be the
primary aviation weather threats from these storms. KCPR could
be the last terminal to be impacted, but confidence is too low
to include into the forecast at this time.

&&

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

&&

$$

DISCUSSION...Dziewaltowski
AVIATION...LaVoie/VandenBoogart