898
FXUS65 KCYS 182326
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
526 PM MDT Fri Apr 18 2025

.KEY MESSAGES...

- Winter Storm Warnings and Winter Weather Advisories remain in
  effect through this evening. Continued snowfall expected
  through the day.

- Warmer and slightly drier Sunday through Tuesday. Windy
  conditions possible Sunday night and Monday.

- Another period of  unsettled weather expected mid to late
  week with numerous showers and widely scattered thunderstorms.

&&

.SHORT TERM /THROUGH SATURDAY NIGHT/...
Issued at 210 PM MDT Fri Apr 18 2025

Radar returns show precipitation slowly decreasing across the area
this afternoon. Many of the Winter Storm Warnings were able to come
down earlier in the day, but a few Warnings and Winter Weather
Advisories remain in place until this evening to account for areas
of blowing snow and some lingering snow. These remaining headlines
look on track to come down on time as Hi-Res guidance shows shower
activity dying down by this evening. Some lingering snow showers and
potentially fog will be possible overnight along the Interstate 80
corridor in Wyoming.

Heading into Saturday, the upper-level trough will still be in place
over the CWA. This means that the cold, below average temperatures
will also stay in place. Low temperatures Saturday morning will be
quite cold as 700 mb temperatures sit in the 10th percentile of
NAEFS climatology. This anomalously cold air will lead to low
temperatures early Saturday morning in the teens and 20s.
Temperatures in western Nebraska will heat up quickly into the 50s
due to mostly sunny skies and minimal snow cover. Southeast Wyoming
will remain on the chillier side with 40s along the Interstate
25 corridor, and upper 30s along the Interstate 80 corridor.
Temperatures out west will be particularly cold due to snow
cover. Although chances are slim, cannot rule out a few snow
showers in the high terrain during the day Saturday as a
vorticity max hangs over the CWA with some leftover mid-level
moisture. Any showers that do develop are not expected to be
impactful. The precipitation threat will taper off Saturday
night as winds become stronger and more westerly.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
Issued at 210 PM MDT Fri Apr 18 2025

An area of surface high pressure moves into the
intermountain west following the trough responsible for the mountain
precipitation on Saturday. This results in a weak upper level ridge
that isn`t very amplified and easily flattened.  Another shortwave
starts to push into our region Monday morning. This shortwave is
pretty weak and not likely to overcome the downsloping westerly
flow. Looking at model soundings, there is a little bit of
saturation in the mid levels and a stout dry layer in the lower
levels. Virga seems the more likely result of this shortwave given
the environment. However, the rain chances may not really occur until
Monday night into Tuesday morning as it will be easier to saturate
in the overnight period and in the morning. Tuesday throughout the
day looks rather dry as the dry lower layer remains in the model
soundings. Wednesday becomes very muddled in the long term. The
deterministic models have reached an agreement of the possibility of
showers forming along this southern boundary. However, it seems like
the moisture advection doesn`t reach our area until late Wednesday
morning with the stronger forcing to the north of our forecast area.
NAEFS places PWAT values between 0.25 and 0.35 inches across the
state of Wyoming and 0.35 to 0.50 values for the Nebraska Panhandle
around 18z Wed. So its more likely if showers do occur Wednesday
they would be more likely in the afternoon during the strongest
moisture content and peak heating for some possible afternoon garden
variety thunderstorms. The global models look to throw in a couple
hundred joules of CAPE in the afternoon and evening.

&&

.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 520 PM MDT Fri Apr 18 2025

A trough aloft will remain over the terminals through Saturday.

Wyoming TAFS...For Rawlins and Laramie, Scattered to broken
clouds from 3500 to 8000 feet will prevail, with occasional fog
reducing visibilities to 3 miles at Laramie from 04Z to 08Z.

For Cheyenne, ceilings will lower to 800 to 1000 feet from 06Z
to 14Z, with areas of fog reducing visibilities to 1 to 3 miles,
then ceilings will improve to 4000 feet after 14Z Saturday.

Nebraska TAFS...Scattered to broken clouds from 4000 to
6000 feet will prevail, with occasional light snow reducing
visibilities to 2 miles and ceilings to 2500 feet at Chadron and
Alliance until 02Z.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...Winter Storm Warning until 6 PM MDT this evening for WYZ106-
     109-110-116-117.
     Winter Weather Advisory until 6 PM MDT this evening for WYZ107-
     108-113-115-118-119.
NE...None.

&&

$$

SHORT TERM...SF
LONG TERM...MM
AVIATION...RUBIN