-- Discussion containing changed information from previous version are highlighted. --
433
FXUS65 KCYS 230214
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
814 PM MDT Sun Sep 22 2024

.KEY MESSAGES...

- Patchy frost is possible once again tonight in low-lying and
  wind sheltered areas.

- Above average temperatures and dry conditions expected for the
  second half of the work week, with increased fire weather
  concerns Wednesday onward.

&&

.UPDATE...
-- Changed Discussion --
Issued at 812 PM MDT Sun Sep 22 2024

No major changes with the forecast update this evening. Modified
dewpoint temperatures a few degrees as observed values were not
matching forecast values. Updated overnight lows, but no major
changes there. Still expecting a chilly night with some of the
low-lying and/or wind-sheltered areas possibly seeing freezing
temperatures. Gusty winds associated with an increased pressure
gradients across the region will keep many locations from
cooling too rapidly, despite the clear skies overnight.
-- End Changed Discussion --

&&

.SHORT TERM /THROUGH TUESDAY NIGHT/...
Issued at 300 PM MDT Sun Sep 22 2024

It has turned into a pleasant fall day across most of the area
today. The upper level low that just missed giving some rain to our
area is now ejecting eastward out of northern Colorado. An
associated cloud shield is still circulating over far southeast WY
and the southern NE panhandle, but clouds will continue to clear
over the next few hours. Surface high pressure has settled into
eastern Colorado, while the next pressure trough is currently
located near the Carbon/Albany county line. A decent pressure
gradient is in place across the area tonight, pushing south to
southeast winds over the plains, and southwest winds further west.
As the pressure trough jumps east of the Laramie range overnight
tonight, westerlies will spread towards the I-25 corridor. Even
though clear skies are expected tonight, the pressure gradient
should keep enough of a breeze going through the night to prevent
widespread frost or freezes. Still, low-lying and wind sheltered
areas will be able to develop a very shallow surface inversion and
could see some patchy frost or near freezing temperatures. The most
likely area for this is low creek beds over the High Plains,
particularly around the Pine Bluffs area.

A quick and transient ridge will briefly build in Monday across the
area. 700-mb temperatures will climb to around +8 to +10C Monday
afternoon before the next shortwave trough arrives late in the day.
Temperatures will warm quickly back to above normal values for this
time of year, with west to northwest breeziness producing some
elevated fire weather conditions. Clouds will increase rapidly from
the northwest to southeast in the afternoon hours just ahead of a
modest cold front which will push through shortly after. While a few
showers can`t be ruled out along and behind this frontal boundary,
the chances for measurable rainfall are pretty low. Tuesday looks
like a very nice day with highs near average for this time of year
and clouds decreasing through the day as the trough moves out and
ridging starts to build back into the area.

&&

.LONG TERM /WEDNESDAY THROUGH SUNDAY/...
Issued at 300 PM MDT Sun Sep 22 2024

Quiet weather expected in the long term as a strong ridge of high
pressure sits over the Rockies on Wednesday. 500 mb heights climb to
about 588 to 590 decameters, which is fairly anomalous for this
time of year. Temperatures on Wednesday will be about 10
degrees above average. Although the upper-level ridge axis will
be overhead on Wednesday, Thursday looks like the warmest day of
the week as winds turn more westerly ahead of a shortwave that
will pass well to the north of the CWA. Breezy downsloping
winds, plus 14C to 15C 700 mb temperatures aloft will make for a
toasty late September afternoon with highs 15 to 20 degrees
above average. Some locations will even be within a few degrees
of their record high! Highs west of the Laramie Range will max
out around 80 degrees, while locations east of the range will be
in the 80s, with even lower elevation spots expected to make it
into the low 90s! Weak ridging Friday into Saturday will lead
to slightly cooler high temperatures, but the area can still
expect these temperatures to be above average for the end of
September. Precipitation chances Wednesday through Sunday will
basically be zero as sunny skies dominate through this period.
However, more fall weather may be on the horizon as long range
models show a trough rapidly digging south into the CWA Sunday
night into Monday with a strong cold front in tow.

&&

.AVIATION /00Z TAFS THROUGH 00Z TUESDAY/...
Issued at 530 PM MDT Sun Sep 22 2024

Upper level trough, south of the area, is forecast to slowly move
eastward and weaken over the next 24 hours. Decreasing cloudiness
and relatively light winds are expected.

HAZARDS/WEATHER TRENDS: VFR conditions will continue over the next
24 hours with minimal impacts to aviation. The probability of fog
over the Nebraska Panhandle terminals is below 5 percent tonight.

&&

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

&&

$$

UPDATE...AM
SHORT TERM...MN
LONG TERM...SF
AVIATION...SF