-- Discussion containing changed information from previous version are highlighted. --
539
FXUS65 KCYS 262304
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
504 PM MDT Thu Sep 26 2024

.KEY MESSAGES...

- Elevated to critical fire weather conditions will continue
  through the early evening hours today.

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

&&

.SHORT TERM /THROUGH SATURDAY NIGHT/...
Issued at 300 PM MDT Thu Sep 26 2024

It feels like mid-summer across the area today despite the calendar
showing just a few days away from October. The axis of a highly
anomalous ridge is pushing over the area today, and the surface
pressure trough located near the WY/NE border is pulling westerly
downslope flow across most of southeast Wyoming. Chadron has already
broken its daily record high, and other locations are flirting
within a few degrees. With another hour or two to warm still,
expecting a few more records to fall before the end of the day.
Critical fire weather conditions are also ongoing thanks to the
westerly breeze and low RH. Westerly flow should gradually ease
through the afternoon, coming to an end by sunset. The amplification
of the ridge overhead today is primarily due to a shortwave
traversing over the top of it. This is currently visible on
satellite imagery near the Montana/Canada border. An associated weak
cold front will manage to come this far south later this afternoon
and evening, bringing a brief period of gusty north to northeast
winds over the High Plains. This won`t last long though, and winds
should be lighter on Friday. We`ll be hard pressed to find a cloud
in the sky again tomorrow, but it won`t be as hot as today. Even
though highs will be knocked down a good 5-10F off of today`s highs,
temperatures will still be considerably above average, just not
record challenging anymore. The ridge will firmly take hold again
this weekend through, pushing temperatures up by a few degrees for
Saturday. The dominant wind direction at the surface will be
southerly, so we won`t have the downslope enhancement for most of
the area, but highs will probably start to push daily records
once.

&&

.LONG TERM /SUNDAY THROUGH THURSDAY/...
Issued at 300 PM MDT Thu Sep 26 2024

The extended range forecast will remain below normal for
precipitation chances as our period of prolonged drought is favored
to continue the next week or so. Additionally, we will have above
average temperatures overall, with a chance for a couple of cool
fronts to reduce our daily highs by 5-10 degrees. With the extended
forecast anticipated to remain dry, we will be on the fringe of
passing weather disturbances to our north. This will cause our cwa
to be favored for breezy to strong wind gusts, as mountain wave
signatures are modeled to be possible early to middle of next week.

Sunday will entail an amplifying upper level ridge over our cwa,
ahead of an approaching shortwave disturbance further upstream.
Record high temperatures are anticipated for the western NE
Panhandle, should model trends continue the next 2-3 days. High
temperatures in the lower to upper 90s, with low 80s to mid 90s for
the high plains of southeast WY. Very dry conditions will accompany
this weather forecast, and there is the potential for breezy to
gusty winds. Could be a decent shot at elevated to near-critical
fire weather concerns for some areas.

Monday and Tuesday will be accompanied by a cool front from Canada,
but it will be dry once again. Daytime highs in the 60s and 70s will
make for a pleasant couple of days, but still remain slightly above
normal according to climatological records. With the passing cool
front(s), fire weather concerns will diminish for the time being.
Omega fields depict an increase in modeled subsidence aloft coupled
with possible mountain wave activity from Tuesday night into
Wednesday, so we will need to monitor trends in the event that a
High Wind headline is prudent. This would favor a lee-side downslope
regime where compressed air makes surface temperatures warmer along
the South/Central Laramie Range and its adjacent foothills...looking
at the higher chance of 80s east of the Laramie Range and western
NE. By Thursday, another cool front is modeled to quickly propagate
across the cwa, bringing temperatures back down to near-normal
readings for the first week of October.

&&

.AVIATION /00Z TAFS THROUGH 00Z FRIDAY/...
-- Changed Discussion --
Issued at 501 PM MDT Thu Sep 26 2024

Partly cloudy skies and VFR conditions are ongoing for the 00Z
TAF issuance. VFR conditions are expected to remain through the
TAF period. Gusty winds across southeast Wyoming will decrease
over the next hour with mostly light winds expected through the
overnight hours. A low-level jet will kick up over western
Nebraska tonight, leading to gusty conditions at KCDR, KSNY, and
KAIA. KBFF should remain sheltered from the gusty winds, but
low-level wind shear is likely as winds increase from around
10kts at the surface to 40kts 2000ft above the surface. Wind
shear will come to and end early in the morning as the low-level
jet decreases. Expecting clear skies for the afternoon.
-- End Changed Discussion --

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...Red Flag Warning until 8 PM MDT this evening for WYZ417>422-
     427-429-430-432.
NE...None.

&&

$$

SHORT TERM...MN
LONG TERM...BW
AVIATION...AM