209
FXUS65 KRIW 030645
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
1245 AM MDT Wed Jul 3 2024

.KEY MESSAGES...

- Scattered rain showers and thunderstorms Wednesday afternoon
  with severe weather possible across the Bighorn Basin and
  Johnson County. Large hail and gusty outflows the main
  concerns. Elevated fire weather risk across the southern half
  of the CWA.

- More isolated rain showers and thunderstorms Thursday
  afternoon, but severe weather is not expected.

- Mainly dry and a warming trend into the weekend and next week
  with increasing fire weather concerns moving forward.

&&

.DISCUSSION...
Issued at 1224 AM MDT Wed Jul 3 2024

IR currently depicts mainly clear skies through much of the CWA
with some mid level clouds for northern parts along the Montana
state line. This is where some weak rain showers are currently
that will push east and dwindle through the early Thursday
morning hours. Another shortwave will push through by late
morning that will increase the gradient to 6-7mb across the
state leading to some gusty winds, especially for areas along
the I-80 corridor up to 30-40 mph likely. Points north should
see 15-25 mph during peak heating of the afternoon before
diminishing towards sunset and into the overnight hours.

By noon to 1PM Thursday afternoon, isolated thunderstorms will
develop off the Absarokas and push into the Bighorn Basin
becoming more widely scattered by mid afternoon around 3-4PM.
Some gusty outflows and larger hail are possible with the main
concern for Johnson County after around 5PM. This is where the
better ingredients are located. CAPE values over 600-700 J/kg
and wind shear up to 35-40kts, along with better low level
moisture as well. The weak surface boundary will help aid in
the lift off the Bighorns after this time through the evening
hours before pushing to the east by 8PM or so. Overall, a
marginal severe afternoon is projected with Johnson County once
again the area to watch as per usual. Some isolated
thunderstorms possible further south along the front with most
CAMS depicting activity staying north of Riverton to Casper
with low confidence (20%) for anything that far south.
Otherwise, points to the south, elevated fire weather concerns
will be had during the afternoon and early evening hours.

Behind the weak cold front, expect slightly cooler temperatures
for the Fourth with only 70s east of the Divide and 60s to the
west. A weaker shortwave is projected during the afternoon
Thursday that will see more of an isolated scenario across
northern portions of the CWA once again for the same area, but
severe weather is not expected at this time. Weaker winds and
cooler temperatures will see good fire weather conditions for
fireworks later that evening and into the nighttime hours.

Friday and into the weekend through much of next week, expect
mainly dry conditions with a warming trend in store through the
long term forecast. Higher heights centered to the southwest
will build greatly during this time period with increasing
convergence aloft extending ridging into the upper Rockies. With
this, will come a weaker upper level flow allowing for only some
isolated higher terrain airmass storms to develop each
afternoon with some possible outflows to the lower terrain. No
impacts expected except for increasing drought and fire weather
concerns going forward through the month of July. Longer term
outlooks show warmer and dry than average conditions going
forward not looking too well going forward in these areas.

&&

.AVIATION /06Z TAFS THROUGH 06Z THURSDAY/...
Issued at 1026 PM MDT Tue Jul 2 2024

A couple showers continue to approach KCOD this evening, but are
expected to finally die off by 06Z. Tonight will be VFR with
minimal clouds and light winds. Gusty winds return across the
state Wednesday, with frequent gusts above 30kts at most sites,
especially KBPI/KPNA/KRKS. More numerous showers and
thunderstorms will build up across northern WY in the afternoon,
with gusty winds and lowered cigs possible at
KCOD/KWRL/KGEY/KBYG. Models continue to limit shower getting any
farther south, so have kept any precip notes from TAFS at KRIW
and KCPR. Precip will end early evening with loss of daytime
heating, but gusty winds will likely continue until 06Z/Thu.

&&

.FIRE WEATHER...
Issued at 1224 AM MDT Wed Jul 3 2024

Elevated fire weather concerns for southern areas along the I-80
corridor and extending through Fremont and Natrona Counties
Wednesday. Winds will be strongest for Sweetwater county with
westerly winds gusting up to 30-40 mph through peak heating of
the afternoon. Points north will see breezy conditions 15-25
mph. Relative humidity values will drop into the 10-15 percent
range for this entire area but with green-up conditions
continuing, only an RFD will be issued from noon Wednesday
through the afternoon and early evening hours.

&&

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

&&

$$

DISCUSSION...Lowe
AVIATION...Straub
FIRE WEATHER...Lowe