Chadron, Nebraska 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

309
FXUS65 KCYS 221204
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
600 AM MDT Tue Sep 22 2026

.KEY MESSAGES...

- Cool and seasonable temperatures will continue through mid-
  week, with a warming trend expected for the second half of the
  week into the weekend.

- Breezy conditions will be possible across much of the region
  Tuesday and Wednesday, especially across the western Nebraska
  Panhandle.

- Increasing coverage of showers and thunderstorms through
  Thursday, then a brief drying trend for the weekend.

&&

.SHORT TERM /THROUGH WEDNESDAY NIGHT/...
Issued at 215 AM MDT Tue Sep 22 2026

Only minor changes to the short range package as short range
ensembles and synoptic model solutions diverge as we head into
the middle of the week. Primary forecast concern is the plume
of subtropical moisture currently impacting the southern Rocky
Mountains over New Mexico and western Texas. 00z models showing
this moisture plume and associated dynamic forcing close enough
to southeast Wyoming and western Nebraska where we can`t rule
out some rainfall and thunderstorm impacts over the I-80
corridor and possibly further north towards the North Platte
River Valley.

For Tuesday, relatively quiet weather will continue with pretty
stable conditions and low CAPE. Low clouds and fog will linger
across mainly western Nebraska through much of the day under
increasing south to southeast winds. A poorly organized upper
level trough is forecast to lift northeast out of the Great
Basin region later today and into this evening. There should be
enough instability and midlevel forcing to initiate rain shower
activity this evening across mainly Carbon and Albany counties,
but can`t rule out some of this activity making it as far east
as the Laramie Range and into the I-25 corridor. Increased POP
between 15 to 30 percent for the lower elevations. Low end
chance of thunderstorms, so kept Prob thunder pretty low and
mainly confined to the areas with the best forcing...which is
still pretty limited and looks better across northern Wyoming.
High temperatures will rebound into the 70s today as the
midlevel flow shifts into the southwest. Kept the coolest
temperatures across western Nebraska due to low clouds and
fog...which may persist into the mid afternoon hours. Some
locations may not make it out of the low to mid 60s.

For Wednesday through early Thursday, most of the forecast area
is in-between systems early on Wednesday as Tuesday`s upper
level trough lifts north into the northern Plains...and the main
subtropical moisture push will be located over New Mexico and
slowly lifting north. This is where models diverge
significantly. The Canadian and ECMWF show the broad trough and
deep moisture lifting northward into Wyoming, while the GFS
shows more of a southwest to northeast trajectory...barely
brushing the southern most zones and as far north as the I-80
corridor over southern Nebraska. This is significant because
PWATs will be above the 99th percentile for late September with
this moisture surge. All models show enough instability and
forcing to produce bands of rain showers and at least scattered
thunderstorm coverage given these moisture profiles. Kept POP
around 15 to 25 percent on Wednesday, mainly across the I-80
corridor and in the mountains...but expect most of the area to
remain dry due to some short-wave ridging in between
disturbances. Late Wednesday night/Thursday looks to be the most
likely time period to see widespread rainfall, but that greatly
depends on the movement and trajectory of the subtropical
moisture plume and primary upper level disturbance lifting
northward. Lowered max and min temperatures into Thursday to
reflect the trend of cloudy skies and scattered to numerous rain
showers.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
Issued at 338 PM MDT Mon Sep 21 2026

Southeastern Wyoming and Western Nebraska will be under
southwesterly flow aloft as a mid-level ridge begins to build across
the Central United States. With an embedded shortwave trough
propagating across the region Wednesday afternoon combined with
another surge of monsoonal moisture (PWAT again ranging within the
80th and 95th percentile), widely scattered showers and
thunderstorms will be possible, mainly south of I-80. However, no
severe weather is anticipated due to weak instability (MLCAPE ~100-
200 J/Kg) thanks to poor mid-level lapse rates. Temperatures look to
be around or slightly warmer than average, in the low to mid-70s
east of the Laramie Range and mid to upper 60s to the west. A weak
cold front is progged to move through SE Wyoming and the W Nebraska
Panhandle overnight Wednesday into Thursday, which may serve as a
focal point for more shower development into the evening hours.

On Thursday, an additional shortwave trough within the longwave
ridge pattern may result in another round of afternoon and evening
showers and thunderstorms, with slightly cooler daytime high
temperatures behind the front. With an effective bulk wind
difference of only 15-20 knots along with relatively weak
instability (MLCAPE < 500 J/Kg), no organized or severe weather is
expected, despite a post-frontal air mass characterized by dewpoints
in the low to mid-50s across the Panhandle and PWAT exceeding
the 90th percentile yet again. This is rather rare for late
September, but we will certainly take any moisture we can get
despite nothing widespread expected...

The flow regime becomes more zonal on Friday which turns off our
supply for the anomalously rich monsoonal moisture seen the previous
days (PWAT ~0.9"). This will decrease our chances for any meaningful
precipitation and will also be the start of a warming and drying
period into the weekend. We will have to monitor increasing fire
weather concerns into the weekend as long range ensemble guidance
suggests gusty, westerly winds mainly across SE Wyoming, combined
with daytime RH values of 20-25%. Not particularly concerned at this
time as we are still short of critical fire weather thresholds, but
will have to be monitored as we get closer given plenty of dry fuel
and further warming underneath the building ridge. High temperatures
this weekend look to be 5-10 degrees above average, perhaps reaching
80 degrees in areas east of the I-25 corridor.

&&

.AVIATION /06Z TAFS THROUGH 06Z WEDNESDAY/...
Issued at 600 AM MDT Tue Sep 22 2026

Low clouds and patchy fog will continue over the eastern high plains
this morning as south to southeast winds increase later this morning
through the afternoon hours. Conditions will slowly improve from
west to east, with KAIA and KSNY hanging on to IFR conditions
possibly until 19z to 20z this afternoon.

HAZARDS/WEATHER TRENDS: IFR to LIFR conditions continue for all
western Nebraska terminals and KCYS. Expect these conditions to
slowly improve to VFR from west to east...by 15z for KCYS, and
closer to 19z-20z for KAIA and KSNY. Winds will then shift into the
southeast and increase this afternoon through late this evening as
the low level jet sets up across the central plains. Further west, a
few lines of showers and embedded thunderstorms possible after 22z
for mainly KRWL, KLAR, and KCYS. Kept PROB30 groups due to low
coverage with brief gusty winds the primary threat.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...None.
NE...None.

&&

$$

SHORT TERM...TJT
LONG TERM...NB
AVIATION...TJT