Carpenter, Wyoming Weather Forecast Discussion

504
FXUS65 KCYS 231147
AFDCYS
Area Forecast Discussion
National Weather Service Cheyenne WY
545 AM MDT Tue Sep 23 2025
.KEY MESSAGES...
- A cold front and Pacific storm system will bring much cooler
  temperatures and unsettled weather Tuesday. Mountain snowfall
  is expected above 8500 feet.
- A ridge of high pressure aloft will lead to drier and warmer
  weather for Thursday through the weekend.
&&
.SHORT TERM /THROUGH WEDNESDAY NIGHT/...
Issued at 250 AM MDT Tue Sep 23 2025
Current KCYS radar loop early this morning shows increasing
coverage of rainfall with embedded heavier shower activity
across most of southeast Wyoming and the southwestern corner of
the Nebraska Panhandle. IR Watervapor shows the upper level
trough closing off as a upper low at this hour across far
northwest Colorado. All models show this low slowly tracking
eastward near the Wyoming border before becoming an open wave
again as it heads into the central plains tonight. High res
guidance and synoptic models are in good agreement, showing the
steady rainfall growing in coverage and extending south into
northern Colorado as we get into the wrap around precip band
this afternoon into this evening. Will likely see rain amounts
between 0.40 to 0.90 inches with locally higher amounts. Surface
observations already show snow over 9500 feet in the
mountains...with Vedauwoo and the I-80 summit coming really
close to 35 degrees at this hour. Will likely see the first few
snow flakes falling at the I-80 Summit sometime this morning.
Otherwise, the Winter Weather Advisory remains on track with
SNOTEL sites recording precipitation with temperatures between
32 to 35 degrees already. The other mountain locations,
including the I-80 Summit, will likely see slushy snow
accumulations of 1 to 2 inches...mainly on elevated and grassy
surfaces. Otherwise, it will be a chilly rain for the lower
elevations through the day today. Lowered high temperatures a
few degrees lower due to overcast skies and widespread rain. The
only exception will be east central Wyoming and the
northern/central Nebraska panhandle which should see breaks in
the clouds and rain ending earlier in the day.
For tonight, models have continued to show freezing or slightly
below freezing temperatures west of the I-25 corridor. With the
10th to 25th percentile ensemble spreads (GEFS and GEPS)
showing upper 20s to 30 degrees for lows for Rawlins, Laramie,
and Saratoga, decided to issue a Freeze Watch for the lower
elevation zones, including the northern Snowy Range foothills
tonight through early Wednesday morning. Do not expect all of
these locations to get below freezing, but a solid frost appears
likely as well. The only thing to keep temperatures from
falling too low will be the expected onset of fog. Added patchy-
areas of fog to the lower elevations with models starting to
pick up on this trend. Either way, it will be quite cold with
either lows below freezing or a decent frost with light winds
and ample low level moisture present. Further east, models have
slowed the exit of the upper level low/trough by several hours
and now show skies struggling to clear after midnight. Kept low
temperatures in this area in the low to mid 40s and will
continue to monitor sky trends for tonight.
For Wednesday, all models show the Omega Block across the Great
Basin Region drifting eastward towards the Continental Divide.
Although northerly flow is expected to continue, 700mb
temperatures will rebound and increase between 4 to 8 degrees.
This will lead to the start of the warming trend with highs
returning to the 60s and low 70s (warmest below 4500 feet).
Another chilly night Wednesday night due to the drier airmass,
so will need to watch for low temperatures trending lower than
current guidance, especially along and east of the Interstate 25
corridor. Kept lows between 38 to 45 degrees for now, with near
freezing temperatures west of the Laramie Range.
&&
.LONG TERM /THURSDAY THROUGH MONDAY/...
Issued at 314 PM MDT Mon Sep 22 2025
An upper level ridge will keep things rather dry
starting Wednesday. Following the trough that pushed through the
Intermountain West, a amplified ridge sets in. The strong
subsident flow is expected to suppress any rising motion to
decrease any rain/snowfall chances. 700mb temperatures look to
remain stagnant between 9 to 11C Thursday through the weekend.
So temperatures look to remain the the 70`s in Wyoming with low
to mid 80`s in the Nebraska Panhandle. Friday into Saturday, an
upper level trough traverses across the Canadian Providences as
well and another trough pushing into the southern California
coast. The southern trough will inject some moisture into the
region however will strengthen the ridge over the intermountain
west as the Rex Block sets up. The northern trough will compress
the ridge to give us a dry but gusty weekend. Our next
precipitation chances after the weekend may come Monday
afternoon with another shortwave pushing through the
intermountain west.
&&
.AVIATION /12Z TAFS THROUGH 12Z WEDNESDAY/...
Issued at 545 AM MDT Tue Sep 23 2025
Upper level low pressure system will move along the Colorado/Wyoming
border this morning. Expect widespread IFR to LIFR conditions to
continue with moderate to heavy rain at times, isolated afternoon
thunderstorms, and some fog for the terminals along and near the
Interstate 80 corridor into western Nebraska. Conditions aren`t
expected to improve until late this afternoon or this evening.
HAZARDS/WEATHER TRENDS: IFR to LIFR conditions will continue at KLAR
and KCYS through early this afternoon, with conditions deteoriating
for KSNY shortly. Further north, MVFR CIGS and VIS are expected at
KBFF, KRWL, and KAIA with off/on shower activity until mid Tuesday
afternoon (21z). All terminals will improve to VFR between 22z and
02z this evening.
&&
.CYS WATCHES/WARNINGS/ADVISORIES...
WY...Freeze Watch from late tonight through Wednesday morning for
     WYZ105-109>111-113-115.
     Winter Weather Advisory until 6 PM MDT this evening for WYZ114.
NE...None.
&&
$$
SHORT TERM...TJT
LONG TERM...MM
AVIATION...TJT

NWS CYS Office Area Forecast Discussion