942
FXUS65 KCYS 101135
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
535 AM MDT Fri Oct 10 2025

.KEY MESSAGES...

- Scattered showers and thunderstorms return to the area today
  through early Sunday.

- A strong cold front will bring strong winds back to the wind
  prone areas Saturday night and Sunday.

&&

.SHORT TERM /THROUGH SATURDAY/...
Issued at 400 AM MDT Fri Oct 10 2025

Current GOES satellite imagery in the water vapor channel shows the
unseasonably strong plume of moisture beginning to move into
southern Wyoming this morning. High water vapor content is apparent
surging straight out of the tropical eastern Pacific from the
weakening Tropical Storm Priscilla. This moisture is caught up in
strong south to southwest flow aloft circulating around the edge of
an upper level ridge currently in West Texas. Precipitable water is
expected to surge to near the climatological maximum with forecast
soundings showing nearly entirely saturated soundings throughout the
atmosphere. While dewpoint records are not carefully maintained, a
quick glance suggests that dewpoints exceeding 50F (and approaching
60F in the Nebraska panhandle on Saturday) will be near October
monthly record highs. Expect fairly thick mid to upper cloud cover
as a result, which should keep daytime highs a little lower both
today and tomorrow. The clouds will of course have the inverse
effect overnight, and both today and tomorrow will have potential to
near record high minimum temperatures.

This sets the stage for the precipitation potential over the next 48
hours, but there remains quite a bit of uncertainty in the details
of the rainfall. Forecasts remain fairly consistent showing limited
forcing for ascent with this system. An upper level vort-max is
currently traversing northeastward over eastern Utah / western
Colorado this morning. This can be seen clearly on infrared
satellite imagery as a region of colder cloud tops preceding
the wave. The feature is expected to move over the area through
the evening hours today, spreading shower activity first into
Carbon County by mid-morning, then slowly spreading eastward
into the early evening hours. Confidence in rainfall is lower
further east. There is a weak signal for some slight overrunning
and/or possible low- level convergence east of the I-25
corridor, which warrants at least some low end PoPs. With the
amount of moisture present, small-scale forcing could easily
kick off more widespread showers than currently depicted in most
global models. As is typical this time of year, instability is
also quite limited today, but models have trended away from
completely zero instability, to something like up to a few
hundred J/kg of CAPE, mostly west of the Laramie range and along
the Cheyenne to Sidney corridor. We could see some isolated
embedded thunder in today`s shower activity.

Expect to see a short break in showers overnight before another very
subtle upper level shortwave returns more rainfall potential
beginning Saturday morning. Weak but nonzero instability will be a
little bit more widespread on Saturday across the area, so thunder
will be slightly more likely as well. Forcing again looks quite
limited, so expect this to be mostly widely scattered showers and
isolated thunderstorms. Despite the impressive moisture, QPF remains
rather unremarkable. Orographic lift should aid the mountains in
getting at least some light to moderate rainfall (snow levels will
be extremely high for October such that even the summit of Medicine
Bow Peak might be seeing rainfall). The valleys of Carbon and Albany
county have approximately a 40 to 60% chance for 0.1" or more of
rainfall, while this remains around 10 to 20% for areas along and
east of I-25. As mentioned before, we will need to watch for local-
scale forcing that can sometimes be missed by NWP models more than a
few hours in advance, as locally heavy rainfall will be possible if
forcing can be produced.

&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...
Issued at 400 AM MDT Fri Oct 10 2025

The next system will be hot on the heels of the weekend moisture.
This will be a powerful upper level trough sweeping in from the
northwest Saturday night into Sunday. Moist, southwest flow ahead of
the frontal boundary will likely return shower activity to Carbon
county late Saturday evening due to orographic lift. Snow levels
will also be dropping closer to October norms during this period, so
rain is expected to transition to snow and drop a dusting to a few
inches on the higher peaks by Sunday morning. However, this system
will be tracking well north of the area, and its dry slot on the
southern flank is expected to be the dominant feature over most of
the area. This will also be the windy side of the system, which will
be the main impact for our area. Gusty southwest winds can be
expected ahead of the frontal boundary Saturday afternoon and
evening, but the main event will be along and after the cold front
sweeps through. Models are coming into better agreement showing
strong pressure gradients developing across the area both at the
surface and aloft. Ensemble mean 700-mb winds are pushing 50 knots
over the wind prone areas which improves confidence in strong winds.
Gradients appear sufficient to produce high winds in the typical gap
wind areas. Probabilities for gusts exceeding 50 knots in the gap
areas are now around 50 to 80%. Models are also showing strong
subsidence through the day Sunday, which will lead to a windy day
for pretty much the entire area. 50-knot gust probabilities are
around 10 to 30% for the High Plains during the day Sunday, but
confidence is fairly high in widespread gusts between 40 and 55 mph.

While very strong, this system will be racing along, and thus the
forcing for strong winds will depart just as quickly as it began.
Look for winds to drop off quickly Sunday evening as a strong
surface high pressure fills in the lee of the Rockies behind the
departing surface low and associated cold front. Expect fairly rapid
surface pressure rises Sunday afternoon into Monday morning. With a
surface high pressure in place, much drier air, and mainly clear
skies, Sunday night brings a decent (50%) chance for a widespread
season-ending freeze. The surface high will not stick around very
long either, pulling eastward off the Rockies by dawn Monday. This
will put a pretty strong reverse pressure gradient over the area,
leading to fairly strong south to southeast winds over the High
Plains Monday. This will also help usher more moisture back into the
area after reaching a minimum on Sunday.

Next week`s weather pattern still includes quite a bit of
uncertainty, but overall we are looking at a fairly unsettled
pattern continuing. A strong closed low is expected to dive into the
West Coast, while the upper level ridge remains over Texas. South to
southwest flow continues aloft with a few disturbances getting
pulled up from Mexico. Low-end PoPs are present for much of the area
Tuesday onward with temperatures slightly above average for the time
of year.

&&

.AVIATION /12Z TAFS THROUGH 12Z SATURDAY/...
Issued at 532 AM MDT Fri Oct 10 2025

Mid to high level cloud cover is moving in this morning and
showers will not be far behind. Confidence is unusually low in
how widespread rainfall will be today, but WY terminals have
some potential for light to moderate rainfall late morning
through the early evening. Scattered showers and possibly an
isolated thunderstorm may linger into the late evening over the
High Plains.

Gusty south to southeast winds will develop around Nebraska
terminals this afternoon, and will strengthen overnight at KCDR.
There is a chance (30%) for low CIGs and/or fog over the High
Plains early Saturday morning.

&&

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

&&

$$

SHORT TERM...MN
LONG TERM...MN
AVIATION...MN