Morton, Wyoming Weather Forecast Discussion

013
FXUS65 KRIW 171845
AFDRIW
Area Forecast Discussion
National Weather Service Riverton WY
1245 PM MDT Wed Sep 17 2025
.KEY MESSAGES...
- Shower activity decreases through the afternoon along and east of
the I-25 corridor. Clearing skies from west to east this evening.
- Dry and warmer weather expected for Thursday and Friday.
- Above normal temperatures are expected to return by Friday and
  continue through much of next week.
&&
.UPDATE...
Issued at 1242 PM MDT Wed Sep 17 2025
As the low rotates eastward, showers across eastern Natrona and
Johnson Counties have continued to decrease in coverage through the
morning. The primary change in the forecast is that hi-res guidance
has significantly backed off on any shower and thunderstorm activity
this afternoon. Thus, expect mostly dry conditions to occur through
the rest of the day with clouds clearing from west to east. The
forecast remains on track beyond today, with a warming and drying
trend, light winds, and no precipitation chances through Friday. It
is still looking likely (70% chance) that temperatures will be
around 5+ degrees above normal for mid-September by Friday, but we
are not expecting record warm temperatures.
&&
.DISCUSSION...
Issued at 153 AM MDT Wed Sep 17 2025
The main weather maker today remains a slow moving upper level
low swirling over the Cowboy State early this morning. And we
continue to have areas of showers swirling across the area, mainly
in central Wyoming. It has brought some needed rain, with over
an inch in some areas around Casper yesterday. And, we could
have some decent rainfall amounts again today as the last in a
series of waves rotates around the low through Wyoming.
Emphasis continues to be east of the Divide, especially our
eastern counties of Johnson and Natrona. Ensemble guidance gives
a greater than 1 in 2 chance of a quarter of an inch of rain
through tonight in this area, although most would fall before
midnight. Areas along and east of Interstate 25 have a 1 in 2
chance of an additional half inch of rain over the same time
period. There could be some localized flooding though if showers
persist over an area. Chances of showers generally decrease as
you go west, with mainly dry conditions expected in far
northwestern Wyoming.
Showers should end after midnight tonight as the last shortwave
exits the area and the upper level low finally gets evicted
into Nebraska and the Dakotas. Ridging should then build into
the area and bring a return to dry and warmer weather for
Thursday and Friday, with Friday looking especially warm with
highs in the 80s for many of the warmer spots.
On Saturday, most of the area should have another dry and warm
day with highs rising into the 80s, possibly a few spots in the
upper 80s in the Bighorn Basin. Just enough moisture may sneak
into the western mountains from the south for a stray shower or
storm, but the chance is less than 1 out of 5 in any particular
location. Things look a bit more active for Sunday as a Pacific
cold front and trough move across the area. The best forcing
and moisture should remain to the north of Wyoming though. It
may be close enough to bring a few showers and storms to
northern Wyoming. The main concern would be elevated fire
weather, as a gusty breeze develops with the passage of the
front and relative humidity will be low ahead of it, falling
into the teens in some locations. Following a brief cooldown for
Monday, dry and warm weather should return for Tuesday and
Wednesday as ridging builds back across the state.
&&
.AVIATION /18Z TAFS THROUGH 18Z THURSDAY/...
Issued at 1103 AM MDT Wed Sep 17 2025
An exiting weather system will bring isolated rain chances to
KCPR through 00Z Thursday. Chances of rain showers with
accompanying MVFR ceilings is around 30%, so maintained a PROB30
group to reflect these chances. Otherwise, dry and VFR flight
conditions are anticipated at all terminals this TAF period with
winds less than 10kts as high pressure builds into the region.
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.
&&
$$
UPDATE...Hensley
DISCUSSION...Hattings
AVIATION...Gerhardt

NWS RIW Office Area Forecast Discussion