Cheyenne, Wyoming Weather Forecast Discussion

863
FXUS65 KCYS 172042
AFDCYS
Area Forecast Discussion
National Weather Service Cheyenne WY
242 PM MDT Wed Sep 17 2025
.KEY MESSAGES...
- Expect widespread showers and isolated thunderstorms to
  gradually decrease in coverage through Thursday morning as the
  slow moving storm system begins to depart.
- Temperatures are expected to warm Thursday through the
  weekend with some minor chances for precipitation during this
  time.
&&
.SHORT TERM /THROUGH THURSDAY NIGHT/...
Issued at 245 PM MDT Wed Sep 17 2025
The slow moving upper level low continues to produce unsettled
weather across the forecast area this afternoon. GOES water vapor
imagery shows two distinct circulation centers associated with the
broader scale trough. The primary upper level low is located over
south central South Dakota, but there is an obvious secondary
circulation that has developed just to the northeast of Cheyenne.
The secondary upper level low is helping to extend the TROWAL to the
southwest, supporting shower activity into Albany county and into
Laramie county. For most of Laramie county, surface winds have
enough of a westerly component that downslope flow will likely
prevent much more than light rainfall, but further west, there is
better potential for another tenth or so of liquid. Temperatures are
quite chilly behind this system. Observations in the Snowy Range
show 2PM temperatures hovering at 33-34 degrees F, indicating there
are likely some flakes flying above about 10,500`. In between the
two upper level lows, a sloppy deformation zone has set up. Forcing
remains sufficient to keep light to moderate rainfall going mainly
north of the North Platte River Valley. We also have some modest
instability still present, so some isolated embedded thunder will
remain possible through the duration of the event. Drier air
wrapping into the secondary upper level low is suppressing rainfall
to the south. Over the next several hours, the expectation is for
the secondary upper level low to begin to break down while the low
to the northeast of us takes over. Once this occurs, expect the
shower activity west of the Laramie range to decrease. The
precipitation shield over the High Plains will then slowly move to
the south and east as the upper level low strengthens and departs.
Expect rainfall to gradually decrease in intensity and coverage as
the evening progresses. Most of the area should be drying out by
midnight, with the exception of possibly the Chadron to Alliance
corridor where decent PoPs are maintained into Thursday morning.
Thursday will kick off with some areas of patchy fog, mainly in
areas where low clouds intersect terrain. The best chance for fog
will be in the Pine Ridge and Laramie Range, and could occur in
parts of Carbon County and along the Cheyenne ridge too, but
confidence is lower there. Skies will gradually clear from west to
east on Thursday with a modest northwest breeze continuing over the
High Plains. Temperatures will remain cool, but with more sunshine,
should be noticeably warmer than today. A surface high is expected
to sneak down from the north in between the Rockies and the
departing low pressure system Thursday night, turning winds to the
east or southeast over the plains as it pushes up against the range.
This may lead to some additional areas of fog and low cloud cover
Friday morning, but this is not included in the gridded forecast at
this time.
&&
.LONG TERM /FRIDAY THROUGH TUESDAY/...
Issued at 245 PM MDT Wed Sep 17 2025
While periods of active weather will be ongoing during the long
term for regions bordering our CWA, our overall area looks to
remain mostly quiet as we move into next week. Friday should see
clearing precipitation but areas of clouds lingering and highs
still in the 70`s for most of the CWA. Moving into the weekend,
we`ll see the influence of a ridge moving in to warm our region
up, but a passing shortwave to the north should bring just
enough energy to produce a few showers or storms mainly in the
high terrain or adjacent regions on both Saturday and Sunday.
Into Monday a strengthening system will pass across and while
we`ll see our temperatures drop once again into the widespread
70`s, the bulk of the moisture associated with this feature will
be to our north and east and precipitation chances are expected
to be overall fairly meager to nil outside of once again the
high terrain. And then by Tuesday ridging starts to build back
in as we`ll see temperatures rising once again to move into the
middle of next week. Overall there is moderate to high
confidence in the forecast with ensembles agreeing on the
overall forecast pattern and the features associated within,
with the primary discrepancies lying with some minor variances
in strength and placement.
&&
.AVIATION /18Z TAFS THROUGH 18Z THURSDAY/...
Issued at 1155 AM MDT Wed Sep 17 2025
Precipitation will continue to move across the region through
tonight, bringing a mixture of all flight categories across all
terminals. Any rain/thunder that move across will primarily
bring these reduced VIS or lowered CIGs, with breezy and erratic
winds possible though not expected on the strong side. Winds
will be overall breezy from a northerly component, with gusts
around 20-30 knots expected. Tonight expect lingering clouds
with occasional showers, with NE Panhandle sites potentially
seeing a return of mist and fog bringing IFR to LIFR conditions
through tomorrow morning. By tomorrow afternoon, precipitation
and clouds should be exiting the region.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...None.
NE...None.
&&
$$
SHORT TERM...MN
LONG TERM...CG
AVIATION...CG

NWS CYS Office Area Forecast Discussion