923
FXUS65 KRIW 301844
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
1244 PM MDT Sun Jun 30 2024

.KEY MESSAGES...

- Widespread elevated to critical fire weather conditions are
  expected through this afternoon.

- Isolated showers and thunderstorms are expected from
  Sweetwater County through Johnson County. Strong outflow wind
  gusts are the main concern.

- Cooler and wetter conditions expected Monday, with the best
  chance of rain across northern Wyoming.

- An active weather pattern will keep temperatures around or
  below normal with continued low chances of precipitation
  through midweek. Warmer and drier conditions are likely toward
  next weekend.

&&

.DISCUSSION...
Issued at 1240 PM MDT Sun Jun 30 2024

Mid/upper level flow has turned more southwesterly today in response
to an approaching trough currently over the Pacific Northwest. This
will be the impetus for our primary forecast concern today. A dry,
mixing southwest wind will become widespread early this afternoon.
Combined with temperatures peaking in the upper 80s west of the
Divide and mid to upper 90s east, relative humidity will drop below
25 percent nearly everywhere and below 15 percent across most
basins. Accordingly, widespread elevated to critical fire weather
conditions are expected through the afternoon. With cured fuels
across much of Natrona County we will continue the Red Flag Warning
there.

Otherwise, modest mixed layer instability (generally up to 500 J/kg)
will develop across southern and central areas by early afternoon.
CAMs have been fairly consistent with isolated convection breaking
out across these areas, specifically from Sweetwater County through
Natrona County. Associated soundings show the the classic inverted-v
boundary layer; with DCAPE values over 1000 J/kg, strong to severe
outflow wind gusts are the main concern with convection today.

Wind and any convection will subside after sunset. However, the cold
front associated with the incoming trough will begin pushing in to
north and western Wyoming this evening, dropping southeast through
the rest of the area through Monday morning. Showers are likely to
sweep along this boundary as moisture returns to the area, with
additional convection likely developing across northern Wyoming as
increased upper level support arrives. Highs Monday will be cooler
behind the front, generally peaking around normal for this time of
year. It will be another breezy day, this time out of the west or
northwest as a lee surface low forms across the Great Plains.

Isolated showers may linger across the area through Tuesday, though
drier air moving in will keep most areas precipitation free. There
will be another surge of colder air during the morning, however, and
highs Tuesday will be even cooler, only peaking into the upper 70s
for most.

Westerly flow keeps Wednesday mostly dry with temperatures
recovering to around normal. However, there is some hints at the
next trough dropping into northern Wyoming Wednesday evening,
bringing another round of convection there. This solution takes the
associated low to our east and then south through Thursday, with
varying degrees on precipitation impacts to our area. For now,
the main impact with this system in the forecast will be another
cooler day on Thursday.

Further ahead, ensemble cluster guidance is favoring an area of
blocking high pressure developing to our west. This would likely
lead to warmer and drier conditions into next weekend.

&&

.AVIATION /18Z TAFS THROUGH 18Z MONDAY/...
Issued at 1135 AM MDT Sun Jun 30 2024

Winds begin to increase at most terminals within the first hour or
two of the forecast period. Gusts 20 to 25kts should be expected at
most terminals through the afternoon, then diminishing by around
sunset. KRKS and KCPR will be the two terminals with the best chance
of seeing any showers or thunderstorms today as Pacific moisture
begins to push through. Spotty convection has been observed across
the south and central portions this morning, but convection will
generally be weak. A few stronger storms would be possible at the
aforementioned terminals late in the afternoon, as diurnal heating
and instability increases.

Monday morning, a cold front will move west to east across the
region. Showers are possible with the front, but confidence is not
high on intensity of these showers, so have included several PROB30
groups to account for any stronger showers or storms that might
occur along and behind the front. The cold front will not bring a
strong wind shift, but gusty west winds will occur ahead of and
behind the front for most terminals Monday 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 1240 PM MDT Sun Jun 30 2024

A gusty and persistent southwest wind will help mix dry air to the
surface. Combined with hot temperatures, relative humidity will fall
below 25 percent for the majority of the area and below 15 percent
for a good chunk of southern and central Wyoming. Elevated to
critical fire weather conditions will continue through sunset before
the wind begins to subside. Otherwise, isolated convection across
these areas could result in strong to severe wind gusts as storms
track to the northeast. Cooler and wetter conditions expected Monday
behind a cold front, with the best rain chances across northern
Wyoming.

&&

.RIW WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning until 7 PM MDT this evening for WYZ280.

&&

$$

DISCUSSION...Myers
AVIATION...Hensley
FIRE WEATHER...Wittmann