-- Discussion containing changed information from previous version are highlighted. --
394
FXUS65 KCYS 270818
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
218 AM MDT Fri Sep 27 2024

.KEY MESSAGES...

-- Changed Discussion --
- Elevated to critical fire weather conditions are possible to
  return Sunday, with minimum humidity in the teens and
  increased wind speeds.

- Warm and dry conditions are expected through the middle part
  of next week.
-- End Changed Discussion --

&&

.SHORT TERM /THROUGH SUNDAY/...
-- Changed Discussion --
Issued at 212 AM MDT Fri Sep 27 2024

Latest surface analysis depicts building high pressure from the
Pacific Northwest pushing eastward into the Intermountain West, with
a cool front digging south from Montana across northern Wyoming and
positioning right along the northern fringes of the CWA.
Observations throughout the night have been once again mild with
temperatures in the high 50s, and even high-60s where
downsloping winds are increasing overnight temperatures, with
clear overhead skies for both southeast Wyoming and the Nebraska
Panhandle.

Slightly cooler temperatures expected today, with a weak surface
front progged to continue digging southward across southeast
Wyoming and the Nebraska Panhandle by the morning hours. Will
see temperatures decline a bit behind the boundary, and dropping
a good 10 degrees from yesterday. However, will still see warm
temperatures persist even under the influence of this boundary
with daytime highs in the low to mid 80s across the I-25
corridor, mid to high 80s for the Nebraska Panhandle, and cooler
for the higher terrains to the west. Moisture advection remains
low for today, with all the good PWATs being much further south
into the Rockies and southern Colorado to do much for our
region.

This weekend will see the return to well above average temperatures
as the upper level ridge once again pushes northward into Wyoming
and Western Nebraska. Kept with the trends over the last few days by
blending in higher NBM percentiles into the short term forecast,
with the NAEFS mean 700mb temperatures in the climatological maxes
both Saturday and Sunday, bringing daytime highs into the high 80s
for southeast Wyoming and into the 90s for the Nebraska Panhandle.
As has been the pattern over the course of the week, forecast
concerns will remain focus on the prolonged dry conditions,
combined with the much warmer temperatures, which will
inevitably raise fire weather conditions as the minimum RH
values drop to the mid to low-teens for much of southeast
Wyoming and the Nebraska Panhandle. Sunday still looks the best
for Red Flag conditions where increased wind speeds will be co-
located with the critical level RH values. However, will hold
off on any headline issues till HiRes model guidance begins
showing higher probabilities for fire weather.
-- End Changed Discussion --

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
-- Changed Discussion --
Issued at 212 AM MDT Fri Sep 27 2024

Dry weather with fast, zonal flow aloft will dominate the long-term
forecast period. Overnight ensemble guidance remains in support of a
surface cold front dropping south through the high plains on Monday
morning. This will end the long stretch of above-normal weather and
return afternoon highs to near climatological averages for both
Monday and Tuesday. The overnight low forecast on Monday night into
Tuesday morning remains seasonably chilly. With dry air and clear
skies in place, we continue to expect an outside chance of scattered
frost in the higher elevation basins including Laramie and possibly
Rawlins. Cheyenne as well as portions of the outlying colder valleys
in the high plains may also see their first frost of the season,
however lows east of the Laramie Range remain on the fringes
(mid 30s) of what would possibly result in some frost at the
surface. Temperatures will rebound on Wednesday as a favorable
downslope flow pattern sets up over southeast Wyoming and
western Nebraska. By Thursday, model guidance begins to diverge
somewhat as a very broad, stretched out trough skirts through
the northern high plains. This system may bring another
reinforcing cold front at the surface southward through the high
plains, reducing temperatures back to seasonable levels by
Thursday. Regarding precipitation, the forecast continues to
look dry through day 7. By Friday evening into Saturday, there
is some indication that a weak upper-level low trapped over the
southwestern CONUS may drift northward through the Central
Rockies and bring a return of showery weather to the mountains.
However, only a very low percentage of ensemble members (less
than 20%) depict this solution with the remaining suite
supporting a dry, almost storm-free pattern. Therefore, we will
favor the drier outcome for the end of next week into the
weekend for now.
-- End Changed Discussion --

&&

.AVIATION /06Z TAFS THROUGH 06Z FRIDAY/...
Issued at 1050 PM MDT Thu Sep 26 2024

Partly cloudy skies will turn mostly clear for the 06Z TAF issuance.
VFR conditions are expected to continue through the TAF period.
Gusty winds expected at KCYS, KCDR, KSNY, and KAIA overnight as a
low-level jet kicks up across the region. KBFF should remain
sheltered from increasing winds, but will likely see winds around
40kts about 2000ft above the surface. Included low-level wind shear
for the KBFF TAF through 12Z. Wind shear comes to an end early in
the morning. Expect clear skies and calm winds throughout the
afternoon hours.

&&

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

&&

$$

SHORT TERM...MRD
LONG TERM...MAC
AVIATION...AM