Natrona, Wyoming Weather Forecast Discussion

167
FXUS65 KRIW 111059
AFDRIW
Area Forecast Discussion
National Weather Service Riverton WY
459 AM MDT Thu Sep 11 2025
.KEY MESSAGES...
- Another day of afternoon/evening showers and thunderstorms
  with gusty outflow winds being the main concern.
- Elevated to near critical fire weather conditions may be
  possible at times today due to low min RH values and gusty
  south/southwesterly winds.
- Chances for showers and thunderstorms increase for Saturday
  and Friday with coverage becoming more widespread.
&&
.SYNOPSIS...
Issued at 304 AM MDT Thu Sep 11 2025
A trough continues to dig across the western CONUS this morning and
will gradually shift east into the Great Basin. This will be the
next weather maker, bringing chances for showers and thunderstorms
through the remainder of the week into the weekend. The overall
trend has been towards a more unorganized system, which would lead
to less precipitation and lower impacts across much of the CWA.
A low will develop in the northern portion of the trough over
MT and ID with a second low attempting to develop farther to the
south. As a result the bulk of the impacts will remain to the
north and south of the CWA. Embedded shortwaves associated with
the trough will move through the region bringing chances for
precipitation in the form of daily showers and thunderstorms.
Long range models indicate the chance for another disturbance
arriving for the first half of next week. As of this morning
impacts would be mainly confined to northern and western WY.
&&
.DISCUSSION...
Issued at 304 AM MDT Thu Sep 11 2025
Showers and an isolated thunderstorm or two are moving across the
state this morning. Conditions should dry out by the late morning
with partly to mostly sunny skies expected through the mid
afternoon. Southwesterly flow increases across the region today as a
deep trough over the western CONUS begins to near. 700 MB winds of
30 to 40 knots move into the region which will lead to gusty surface
winds of 25 to 35 mph throughout the afternoon Thursday.
Temperatures today remain above normal east of the Divide with highs
in the low to mid 80s. Locations west of the Divide look to see more
seasonable temperatures in the low 70s as a result of the nearing
trough. Increasing southwesterly flow will usher in drier air
leading to dewpoint depressions of 45 to nearly 50 degrees in some
locations. A second round of showers and thunderstorms looks to
develop during the afternoon and evening. Due to the overall dryness
of the atmosphere many locations will see little to no moisture
reach the surface. The concern as a result of this dryness will be
strong gusty outflow winds of 40 to 50 mph nearby any showers and
thunderstorms as they develop and collapse. Elevated to near
critical fire weather conditions will be possible in portions
of the state today. The only limiting factor for Red Flag
Warnings are RH values slightly above 15%. So while not fire
weather highlights will be issued, favorable fire weather
conditions will be possible especially east of the Divide.
Friday will start to see conditions shift as the trough axis nears
the area. Cooler temperatures slightly below normal are forecast
west of the Divide with highs in the upper 60s to low 70s. East of
the Divide remains warm but with temperatures beginning to gradually
cool as highs range in the upper 70s to low 80s. Winds increase once
again during the afternoon but with gusts mainly around 20 mph. The
atmosphere remains dry but not to the same extent as Thursday with
lesser dewpoint depressions of only 30 to 40 degrees. Showers and
thunderstorms will be possible once again starting in the early
afternoon and spreading to the northeast into the evening. Coverage
will be more widespread compared to Thursday but the dryness may
limit moisture from reaching the surface in some areas. This dryness
may once again lead to some gusty outflow winds nearby any showers
or storms. Elevated fire weather conditions look possible at times
Friday with lesser concerns due to weaker winds and higher min RH
values around 20 to 30%.
The trough axis enters the area by Saturday with shortwaves moving
across the state through the weekend. This will lead to continued
chances for showers and thunderstorms Saturday through Sunday
morning. Temperatures will continue to cool over the weekend with
highs west of the Divide in the mid 60s and highs east of the Divide
in the mid to upper 70s. Long range models show a brief lull in
activity for most of Sunday before the next disturbance moves in
from the PACNW. The exact impacts from this disturbance remains
unknown as models do not have good agreement regarding the track.
Differing tracks of this disturbance will lead to differing impacts.
A better idea of what to expect should begin to develop by the end
of the week.
&&
.AVIATION /12Z TAFS THROUGH 12Z FRIDAY/...
Issued at 450 AM MDT Thu Sep 11 2025
Isolated showers continue over central and far western portions
of the forecast area this morning. A thunderstorm currently over
the Star Valley may hold together and impact KJAC as it
continues to move northward. This activity is expected to end
by 15Z with mostly clear skies for much of the area. VFR
conditions expected for the entirety of the period for all TAF
sites. Thunderstorm activity increases after 19Z with the storms
moving from the southwest to northeast. This activity will be
widely scattered across the CWA, but all terminals will have a
chance to impacted between 20Z and 00Z. Outside of storm
outflow winds, expect synoptic wind gusts of 25 to 35 kt. Some
of the stronger gusts will be up to 45 kt as a result of the
already higher wind gusts. Most of this convective activity will
end for much of the area by 02Z, however showers will remain
possible through 12Z from southern Lincoln County to the Bighorn
Basin. Confidence remains too low to include any impacts at any
terminal through this time frame.
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.
&&
$$
SYNOPSIS...Dziewaltowski
DISCUSSION...Dziewaltowski
AVIATION...LaVoie

NWS RIW Office Area Forecast Discussion