315
FXUS65 KCYS 101102
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
502 AM MDT Thu Oct 10 2024

.KEY MESSAGES...

- Continued dry and warm conditions are expected through early
  next week with elevated fire weather concerns continuing.

&&

.SHORT TERM /THROUGH FRIDAY/...
Issued at 300 AM MDT Thu Oct 10 2024

Warm and dry weather continues unabated today. Yesterday`s very weak
shortwave is on its way out across the central plains at this time,
while another more significant trough is currently pushing into the
persistent ridge. In between the two features today, we`ll see
decent warm air advection and slightly increased westerly flow. A
light breeze is keeping the boundary layer mixed in some of the
westerly or southerly wind prone areas. This areas are seeing 2AM
temps hold in the mid 50s to lower 60s, which isn`t too far below
typical daily maximum temperatures this time of year. This will lead
us into the warmest day of the week today as the ridge axis shifts
overhead. Expect mid 70s west of the Laramie range, and 80s to
the east. A few spots in the Nebraska panhandle may make a run
for 90. Forecasts match daily record highs at KCDR and KAIA, and
are within a few degrees at all other climate sites. The
westerly breeze will also produce widespread elevated fire
weather conditions, along with briefly critical conditions for
the wind prone areas. While 3 hours of critical conditions
probably won`t be met, any ignitions today could still spread
rapidly as we are over 3 weeks since the last rainfall anywhere
in the area, and at 35 days for Cheyenne and Rawlins.

For those curious about how unusual this dry stretch is, we are not
close to records yet. Most locations have gone over 2 months without
measurable precipitation at some point in their history. However,
the 35 day stretch at Cheyenne and Rawlins will enter the top 10
longest dry streaks on Monday and Wednesday next week respectively,
of course assuming no precipitation between now and then (which
looks likely).

The shortwave will pass over the top of the ridge tonight, resulting
in the most cloud cover we have seen over our area in weeks. This
will hold temperatures up well into the night across the area, but a
weak cold front will flip winds to the north to northeast overnight
and usher in a cooler airmass for Friday morning. Lows will still be
above normal but perhaps not as warm as they would be in the absence
of the new airmass. This airmass will not get far west of the
Laramie range, so temperatures will only be a few degrees cooler
than Thursday there. To the east though, highs 10-15+F cooler than
Thursday are expected, though they still won`t get below average for
this time of year. The cooler/moister air will reduce fire weather
concerns for the High Plains, but Carbon county will remain warm,
dry, and breezy.

Lastly, the smoke/haze will remain in the picture. Westerly/
southerly winds today should lead to improving conditions today, but
it won`t last long as more smoke will probably be caught up in the
northerly flow that resumes this afternoon and into the overnight
hours.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
Issued at 300 AM MDT Thu Oct 10 2024

An active synoptic pattern continues to be likely for the weekend
into early next week, though minimal precipitation chances are
expected at this time. Saturday features a messy ridge across the
Intermountain West, with an upper-level low pushing inland over
California and Nevada. An advancing upper-level Canadian trough
begins to push into the northern CONUS Saturday into early Sunday
morning, which will active to block the upper-level low. The upper-
level low will progress very slowly to the east, allowing for a weak
ridge to remain over the CWA and temperatures in the low-70s to low-
80s.  Sunday, the low moves from southern Idaho to southern Utah
throughout the day as the Canadian trough digs southward, with a
strong jet from North Dakota south to Kentucky and north again to
Maine.

Model disagreement picks up significantly for Monday and Tuesday,
with the GFS keeping the upper-level low nearby through Thursday,
while the ECMWF quickly pick up the low within the upper-level flow
associated with the Canadian trough. The GFS does not push the low
out of the region until Wednesday and Thursday, as an upper-level
ridge develops and absorbs the low into the flow. The ECMWF also
develops another upper-level ridge by Tuesday afternoon. Confidence
is decent in a mid-week ridge developing overhead once again next
week, but the exact progression to get to the ridge is uncertain at
this time. Ridging is expected to remain through Friday.

Looking past the long term forecast period, both the ECMWF and GFS
are picking up on a potent upper-level trough digging across the
CONUS over the weekend. Both models are nearly identical on the
placement of the trough, as well as its strength and progression. If
this trough comes to fruition, this will likely result in the first
widespread freeze of the winter season and may even include some
snow as it pushes overhead. This is still over a week out, but this
potential winter system will continue to be monitored over the
coming days.

&&

.AVIATION /12Z TAFS THROUGH 12Z FRIDAY/...
Issued at 500 AM MDT Thu Oct 10 2024

VFR conditions ongoing across all terminals. Clear skies and
light winds are expected through much of the 12Z TAF period,
with some gusty winds possible at KCYS and KLAR this afternoon.
High clouds return this evening into the overnight hours.

&&

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

&&

$$

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