422
FXUS65 KRIW 291922
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
122 PM MDT Sat Jun 29 2024

.KEY MESSAGES...

- Above normal temperatures, a dry lower atmosphere, and gusty
  southwest wind elevates the fire weather hazard Sunday.
  Critical fuels in Natrona County have led to a Red Flag
  Warning Sunday afternoon.

- Seasonal temperatures return Monday behind a cold front.
  Scattered thunderstorms are most likely across the northern-
  third of the forecast area.

- After a period of generally seasonal temperatures and typical
  afternoon showers and thunderstorms, a ridge of high pressure
  will raise temperatures for next weekend while keeping
  conditions dry.

&&

.DISCUSSION...
Issued at 122 PM MDT Sat Jun 29 2024

Satellite imagery shows isolated convection across northeast
Utah early Saturday afternoon within a plume of mid-level
moisture. Southwest flow aloft allows this plume to track into
southwest Wyoming later this afternoon. Given low dew points and
limited instability, any convection would be weak with little
if any rainfall and generally confined to Sweetwater County
until sunset Saturday. Gusty outflow wind 40 to 50 mph would be
the primary hazard with any convection. Otherwise, dry
conditions and seasonal temperatures prevail overnight as a
low-amplitude ridge axis traverses the region.

The upper flow backs a bit more to the southwest Sunday in response
to an approaching trough moving across the Pacific Northwest and
into the Northern Rockies Sunday and Sunday night. Southwest wind of
20-30kts at 700mb mixes to the surface during the afternoon ushering
in drier air from the southwest. This same flow boosts 700mb
temperatures to 16-18C Sunday afternoon leading to widespread highs
in the 90s. Dew points decrease through the afternoon hindering
convection and dropping relative humidities into the teens. This
favors elevated fire weather conditions across central and southwest
Wyoming. One limiting factor to realizing full heating and low
humidity could be afternoon cloud cover within this region. The axis
of mid-level moisture remains along and south of a line from roughly
Green River to Kaycee, where cloud cover may become a bit more
extensive Sunday afternoon. Isolated convection is most plausible
across the eastern half of Natrona County and neighboring areas.

The incoming trough and associated cold front reaches northwest
Wyoming Sunday evening and pushes east overnight and into Monday
morning. Scattered showers and a rogue thunderstorm or two develop
as moisture spreads across the northern-third of the forecast area.
Jet streak energy and a steady stream of channeled vorticity serves
to enhance convective potential through the day Monday, especially
across the aforementioned northern areas. Daytime high temperatures
Monday cool 8-15F from those of Sunday. Below elevations of 6000
feet, the coolest readings will be across the far north where
readings may not climb out of the 70s. The trough lifts northeast
late Monday night leading to a decrease in precipitation by sunrise
Tuesday. Overnight temperatures will be seasonal.

Cyclonic flow lingers Tuesday keeping daytime highs below normal by
5-8F at many locations, particularly along and east of the
Continental Divide. The far north has the best chance for showers
given the persistent cyclonic flow. Temperatures moderate a bit for
Wednesday, but the last vestiges of the cyclonic flow keeps the
threat of late day convection over the far north through
Thursday. There is also a hint that a surface boundary will push
across areas east of the Continental Divide and cool daytime
highs for Independence Day. The pattern does begin to show
signs of shifting Friday into Saturday as ridging builds along
the West Coast. The overall trend will be toward drier and
warmer conditions beginning Friday on into the weekend.

&&

.AVIATION /18Z TAFS THROUGH 18Z SUNDAY/...
Issued at 1146 AM MDT Sat Jun 29 2024

VFR conditions will prevail through the period. There is a low
chance (less than 20%) of a shower or thunderstorm near KRKS this
afternoon and early evening, but confidence is not high enough to
keep mention of this in the TAF for now. Otherwise, wind will
generally remain on the lighter through this evening. The exception
will be at KCPR which will see a gusty easterly wind from around 0Z
to 06Z. Then, southwesterly wind will begin increasing at most
terminals late Sunday morning.

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 122 PM MDT Sat Jun 29 2024

Unseasonably warm temperatures and gusty southwest wind 20 to 35 mph
will combine to create low relative humidities Sunday afternoon
leading to widespread elevated fire weather conditions. A Red Flag
Warning has been posted for Zone 280 where fuels are now critical. A
dry lower atmosphere will hinder the development of late day showers
and thunderstorms. Any that are able to form would generate outflow
wind gusts of 40 to 50 mph rather than rain of any consequence.
Conditions improve around sunset Sunday and more so Monday behind a
Sunday night cold front.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning from 1 PM to 7 PM MDT Sunday for WYZ280.

&&

$$

DISCUSSION...CNJ
AVIATION...Myers
FIRE WEATHER...CNJ