Chadron, Nebraska 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

373
FXUS65 KCYS 211118
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
518 AM MDT Thu May 21 2026

.KEY MESSAGES...

- There is a Marginal Risk (Level 1 of 5) for severe weather
  Thursday afternoon across western Nebraska and far
  southeastern Wyoming. Isolated large hail and damaging winds
  are the primary concerns.

- Widespread showers and storms come to an end early Friday
  morning before drier weather returns for the weekend.

- Very warm temperatures return for the start of the work week,
  with some locations likely seeing the 90s once again.

&&

.SHORT TERM /THROUGH FRIDAY NIGHT/...
Issued at 206 AM MDT Thu May 21 2026

Active weather days are anticipated both Thursday and Friday, with
additional precipitation chances expected over the weekend. An upper-
level trough is slowly digging into the Intermountain West this
morning, with upper-level clouds starting to push into western
portions of the CWA as of 07Z, per the GOES-19 Upper-Level Water
Vapor Channel and Nighttime Microphysics. This upper-level trough
will continue to push eastward throughout the day today, with some
models hinting at a negatively-tilted trough by mid-day.
Southwesterly flow aloft will dominate ahead of the incoming trough
with strong cyclonic vorticity advection along the trough axis and
multiple vorticity lobes ejecting out ahead into southeast Wyoming
and western Nebraska. The trough will narrow throughout the late-
evening and overnight hours while it models across the CWA aiding in
more concentrated synoptic ascent across much of the area.
Southwesterly to westerly flow is progged at 700mb as the 700mb low
spins, nearly stationary, across southern Saskatchewan. Warm air
advection at 700mb will be present as the CWA remains within the
warm sector of the surface low over far western South Dakota. This
will further aid in additional ascent across the region, but
especially along and east of the Laramie Range. At the surface, the
surface low will struggle to organize over western South Dakota this
morning as it interacts with the Black Hills, but will be closed and
well defined by the evening. Despite this, strong southerly flow is
expected, bringing ample warm air and modest moisture from the
moisture rich regions of the southern CONUS. Afternoon dewpoint
values across the Panhandle are anticipated to surge into the mid-
to upper-40s this afternoon, creating a warm, moist environment from
broad lift from the warm sector and supportive synoptic-scale lift.
As a result, afternoon showers and thunderstorms are anticipated to
develop between 1pm and 3pm east of the Laramie Range, with showers
and storms starting as early as 9am to 11am across Carbon County.
Showers and storms west of the Laramie Range are not expected to be
severe at this time, but there is a Marginal Risk (Level 1 of 5)
from the Storm Prediction Center in an arch from Cheyenne north to
northern Goshen County eastward through Southern Sioux County and
Box Butte County then back south through Sidney. Primary severe
threat at this time is very strong winds and possibly some isolated,
large hail. Forecast soundings from the RAP suggest ample surface-
based CAPE across most areas east of the Laramie Range, between 600
J/kg in southeast Wyoming to 1200 J/kg over western Nebraska. Low-
level turning will be modest with good directional shear, but poor
speed shear. Ample CAPE is available within the Hail Growth Zone,
favoring the potential for large hail to develop. Additionally, bulk
shear is decent, between about 35kt and 50kt, depending on location.
The strongest shear will be along the I-80 Corridor from about
Kimball east to Sidney, but decent shear remains from Cheyenne to
the Nebraska state line. Given this environment, an isolated
supercell or two will be possible, especially in western Nebraska,
this afternoon with hail and wind being the primary threats.
However, an isolated tornado cannot be completely ruled out due to
low-level turning across this area.

The cold front associated with the surface low is progged to push
northwest to southeast across the CWA between about Noon and 6PM.
Behind the front, temperatures will drop fairly quickly, with
continued precipitation development along and behind the front.
Therefore, Thursday night looks quite wet across the region with the
possibility for some rumbles of thunder in the east after the
potential severe weather in the afternoon. As the surface low spins,
multiple bands of precipitation will develop due to lingering
moisture and ascent, so precipitation will come in waves overnight.
West of the Laramie Range, much cooler 700mb temperatures filter in
behind the front, bottoming out around -5 to -3C. With cooler air,
moisture, and continued ascent, locations west of the Laramie Range
will likely see isolated to scattered snow showers overnight
Thursday into the early morning hours Friday before diurnal heating
returns. Significant accumulations are not anticipated at this time,
likely between a trace to half an inch in the lower elevations. The
mountains may see between 2 and 5 inches of snow overnight into the
morning hours Friday. Temperatures Thursday night will tumble back
to around 28 to 32F, just above frost advisory criteria. However, if
the system comes in a bit cooler than currently anticipated, a short-
fuse Frost Advisory may be needed for Carbon and Albany Counties
overnight Thursday into Friday morning. There is low confidence in
the potential for widespread and long duration frost conditions,
therefore, no Frost Advisory was issued with this forecast update.

Moving into Friday, the initial trough associated with the
precipitation for Thursday will advect off to the northeast early
Friday morning through the mid-morning hours as precipitation
chances start to taper off. A brief period of zonal flow is expected
to develop as another short-wave trough moves into the CWA from the
west. This shortwave currently looks to remain largely neutral to
positive in tilt, though ample 500mb vorticity advection will be
present with multiple vorticity lobes ejecting out ahead of the
second incoming trough. There will be a period of 700mb warm air
advection in the afternoon hours as the 700mb low slowly moves
northeasterly and before the second upper-level short-wave moves
through. At the surface, northwesterly flow will continue through
the morning and early afternoon hours, before switching
southeasterly to easterly late evening into the overnight hours.
With this timing, airmass recovery does not look good throughout the
day Friday, despite the warm air advection at 700mb. Northwesterly
flow will act to dry out the surface level as modest downslope
develops to the southeast of the Laramie Range, preventing a good
airmass recovery. Most models are not onboard with precipitation for
Friday afternoon and evening, though a few suggests some isolated
showers overnight Friday into the early morning hours Saturday.
While precipitation cannot be completely ruled out Friday afternoon,
it is becoming less likely as models continue to suggest poor
airmass recovery behind the initial cold front. In addition to this,
Friday high temperatures are expected to remain in the upper-40s to
low-50s west of the Laramie Range and mid-50s to low-60s east of the
Laramie Range. These temperatures could be enough to get an isolated
shower to develop, but overall the setup looks weak. Temperatures
Friday night will drop back to the low-30s to low-40s
everywhere.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
Issued at 206 AM MDT Thu May 21 2026

No major changes with this forecast update. Precipitation
chances increased for Sunday evening and Monday afternoon.
Please see previous discussion...

The cool and unsettled weather pattern will come to a close this
weekend as broad troughing is replaced by zonal flow on Saturday,
followed by building ridging Sunday through Tuesday. Expect a
pleasant day on Saturday with temperatures near seasonal averages.
Typical diurnal cloud cover and winds can be expected with some mid-
level cumulus and westerly breeziness developing in the afternoon.
Isolated high based showers and a few thunderstorms will be
possible, though the chance for appreciable rainfall is fairly low.
A potent upper level ridge will build into the area Sunday into
Monday, pushing temperatures above seasonal averages. 700-mb
temperatures climb to around +8 to +12C, which will support highs
around the climatological 90th percentile, but still several degrees
shy of daily record highs. Chances for a few afternoon and evening
high based showers and thunderstorms will continue Sunday and
Monday, but again, rainfall potential will be limited. With westerly
flow prevailing at the surface, dewpoints will remain stuck mostly
in the 30s. Forecast soundings show decent moisture aloft, but
fairly deep, dry, and well-mixed boundary layers. In addition,
forcing for ascent looks limited. NBM PoPs are not really showing up
for this period yet, but this is a fairly typical bias during warm
and dry weather.

Tuesday will be another warm day, but hints of a more active pattern
to come will begin to show up. The strong upper level ridge will
shift eastward, setting up over the Plains and Midwest. Meanwhile, a
closed upper level low will dive into the Pacific Northwest and then
stall for several days as it inches eastward. Falling surface
pressure over Montana associated with modest lee cyclogenesis will
increase southerly flow Monday into Tuesday, which should allow low
level moisture to recover. Forcing from the approaching upper level
low will help ignite showers and thunderstorms in the place of
modest instability and ample moisture. This should setup Tuesday as
the best day for more widespread shower and thunderstorm activity.
The upper level low will be very slow to move eastward, which may
keep scattered to numerous showers and thunderstorms as a
possibility for much of next week. NBM PoPs of generally 20 to 50%
Tuesday and Wednesday afternoons appear appropriate at this time,
considering we are still 6-7 days away.

&&

.AVIATION /12Z TAFS THROUGH 12Z FRIDAY/...
Issued at 512 AM MDT Thu May 21 2026

A very narrow band of fog and low clouds has developed just
over and west of the KCYS terminal. The fog bank has sloshed
back and forth from west to east, leading to visibilities from
1/2SM to 2SM and higher. This band should erode by 14Z this
morning. Patchy fog is also ongoing across western Nebraska, but
is only slightly impacting KAIA at this time. All fog should
error after about 14Z this morning, as high clouds move back in
across much of southeast Wyoming and western Nebraska. Isolated
to scattered showers and thunderstorms are anticipated this
afternoon with scattered to widespread showers and storms
expected after about 21Z this afternoon. Showers and storms will
continue into the overnight period, decreasing ceilings and
visibilities at most terminals. Showers and storms come to an
end well after the 12Z TAF period concludes.

&&

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

&&

$$

SHORT TERM...AM
LONG TERM...MN/AM
AVIATION...AM