118
FXUS65 KRIW 150302
AFDRIW

Area Forecast Discussion
National Weather Service Riverton WY
902 PM MDT Fri Jun 14 2024

.KEY MESSAGES...

- Isolated thunderstorms will produce 45 to 55 mph outflow wind
  gusts this evening through sunset, after which time storms
  will dissipate.

- Temperatures continue to run 10 to 15 degrees above seasonal
  normals through the day Saturday.

- Breezy winds are expected on Saturday combined with
  temperatures well above normal, leading to elevated fire
  weather conditions. Shower and thunderstorm activity will be
  minimal.

- Temperatures begin cooling on Sunday, and below average
  temperatures are expected by Tuesday as the next weather
  system moves through.

&&

.DISCUSSION...
Issued at 255 PM MDT Fri Jun 14 2024

A strong ridge of high pressure continues to dictate the weather
pattern for Wyoming over the next 36 hours, with temperatures
remaining 10 to 15 degrees above normal. As a trough slowly
pushes onto the West Coast this afternoon, a shortwave focused
over Montana has provided lift for some thunderstorms, primarily
across southern Montana, just north of the Wyoming border. Over
western and central Wyoming, dynamics are not as favorable, but
scattered diurnal-heating-based "garden variety" thunderstorms
will still produce gusty outflow winds on the order of 45 to 55
mph due to the large temperature-dew point spreads (indicative
of efficient evaporation and cooling of downdraft air parcels).

After sunset storms will quickly dissipate. Overnight RH
recovery will be relatively poor and thermal belts are likely
for midslopes. Any fire activity is likely to be more vigorous
than on a typical overnight.

On Saturday, the trough over the Pacific Northwest will continue
inching eastward, tightening the pressure gradient. Most areas
across Wyoming will see strong sustained westerly winds develop
by noon, with gusts in the 35 to 50 mph range. The higher gusts
will be focused over the wind corridor from Sweetwater to
Natrona County. Isolated thunderstorms are again possible on
Saturday afternoon, but these will be focused over the Powder
River Basin and quickly move into eastern Wyoming by mid-
afternoon. Gusty outflow winds are again the main threat with
any of this convective activity.

Sunday and into early next week the trough to the west will
begin to influence sensible weather more. Temperatures will
cool to seasonal normals, and areas along the northern third of
the state will likely (40 to 70% chance) see light measurable
rain Monday into Tuesday. Tuesday will even feature temperatures
below seasonal normals for the first time in over a week.
Temperatures moderate for the second half of the week, with
above average highs again in the forecast by Friday.

&&

.AVIATION /06Z TAFS THROUGH 06Z SUNDAY/...
Issued at 902 PM MDT Fri Jun 14 2024

Some lingering rain showers and thunderstorms are near KRKS/KPNA
thanks to a rogue outflow boundary that is moving northwest. This
outflow boundary looks like it has finally stalled just southeast of
KPNA, so no new convective development is expected with this tonight
as the recent convective activity dissipates. Conditions will remain
VFR through the TAF period. Model guidance is now depicting
convective development in Natrona and Johnson County Saturday
afternoon, which means a chance for storms in the vicinity of KCPR
for a couple of hours. Strong surface winds should prevent any rogue
outflow boundaries associated with this convection from pushing west
and initiating more convection in the area, so thinking is just a
short window for thunderstorms at KCPR Saturday afternoon. Wind will
increase Saturday morning and become strong across the area through
the afternoon. Wind gusts will average 25-35 knots (as high as 45
knots) Saturday afternoon.

Please see the Aviation Weather Center and/or CWSU ZDV and ZLC for
the latest information on icing and turbulence forecasts.

&&

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

&&

$$

DISCUSSION...VandenBoogart
AVIATION...Rowe