809
FXUS65 KRIW 141127
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
527 AM MDT Fri Jun 14 2024

.KEY MESSAGES...

- Some waterways continue to run high for at least the next 24
  hours.

- Hot and mainly dry Friday with some isolated thunderstorm
  activity east of the Divide.

- Elevated fire weather risk Saturday with gusty winds and low
  humidity.

- A cooler and more unsettled pattern for late Sunday through
  mid next week.

&&

.DISCUSSION...
Issued at 1238 AM MDT Fri Jun 14 2024

Current IR depicts a low to the southwest over southern
California pushing ample mid to upper level moisture into the
upper Rockies and the CWA. Some lingering rain showers east and
southeast of the Winds that will push eastward through sunrise
Friday morning. Some stronger storms are pushing into
Yellowstone as well with some gusty outflow coming out of Idaho
as indicated with some observations. These should diminish as
well moving into a more stable environment less favorable to
stay in tact as the night moves on.

Otherwise, another warmer than average temperature afternoon for
the entire CWA. A weak shortwave will spin off an upper level
low nearing the Pacific northwest coast supporting a weak
frontal boundary draped across the northern border with Montana.
This will slowly pushed east and southeastward during the
afternoon sparking some isolated thunderstorms with peak
heating east of the Divide. The main concerns for stronger
outflows will be across northern parts of the CWA and especially
through the Bighorn Basin. This is where the greatest
destabilization will occur with CAPE values over 600-700 J/kg.
Sufficient enough shear will be present to allow for possible
stronger storms to see wind gusts up to 50-60 mph. Confidence
low at this point (only 10-20% severe possibility) as much of
the much better ingredients being well eastward into the high
plains.

With this slow moving front, it will tighten the gradient for
Saturday seeing 6-7 mb spreads through the CWA. By late morning
and especially for peak heating of the afternoon and strongest
mixing to the surface, wind gusts up to 40-50 mph are likely
with the wind prone areas the strongest across the I-80 corridor
and through the Rattlesnakes to the Casper area. Combined with
low relative humidity values, elevated fire concerns are
present, even with green-up across most of the area. Any storm
activity will be constrained to higher elevations of the
Bighorns and Winds to the northern Absarokas with no significant
impacts expected at this time.

The stronger cold front will push through Sunday with timing not
solidified with ample discontinuity between a multitude of
models. Thus, temperatures will fluctuate at this point in time
dependent on FROPA with warmer highs further south and cooler
behind it to the north. Precipitation chances and cooler
temperatures will come with the front late Sunday and into the
first half of next week. Accumulation amounts are uncertain at
this point as well but looks to impacts the northern half of the
CWA as models are more aligned to the northern path of the
aforementioned upper level low to the northwest. The low looks
to fill with its eastward progression with decreasing divergence
aloft and thus, QPF amounts do not look to have a big impact.
Models are even hinting at some higher terrain snow above 7-8kft
with minor accumulation`s possible. Lower areas will remain
liquid rain with chances through Wednesday.

The low will elongate into an upper level trough as it becomes
more progressive through the upper Rockies quickly pushing into
the Great Plains by late Wednesday. Upper level ridging will
build back in from the south for the rest of the work week and
into the next weekend. Dry conditions and a warming trend will
return heading into the later stages of the month of June.
Hopefully, some decent rainfall and moisture will occur with
this upcoming system Sunday night through Wednesday morning as
precipitation chances outside of this time frame look to be
minimal at best moving forward.

&&

.AVIATION /12Z TAFS THROUGH 12Z SATURDAY/...
Issued at 521 AM MDT Fri Jun 14 2024

Conditions will remain VFR through the TAF period, unless a strong
thunderstorm moves directly over a terminal Friday afternoon. If
that occurs conditions may drop to MVFR briefly with reduced VIS.
Wind will be light (5-10 knots) this morning and then will increase
into the afternoon as a weak cold front moves through the area.
Gusts will be 20-25 knots on average Friday afternoon. Scattered
rain showers and thunderstorms continue across portions of the CWA
this morning, and will linger through the afternoon as this front
moves through. KJAC is seeing localized shower activity now, and
there is a band heading toward KCPR as well.

The best chance for thunderstorms later today in the vicinity of a
terminal will be at KCOD as convection develops along the eastern
slopes of the Absarokas and moves east with the general flow. So,
have included VCTS at KCOD Friday afternoon. A lower chance for
showers and storms at KWRL for Friday afternoon, so included a
PROB30 group with -TSRA. Strong wind gusts around 40 knots will be
possible (40-50%) with any thunderstorms that develop.

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...Lowe
AVIATION...Rowe/Swanson