683
FXUS65 KCYS 060211
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
811 PM MDT Sat Oct 5 2024

.KEY MESSAGES...

- Critical fire weather conditions will continue today with Red
  Flag Warnings through early this evening. A passing weather
  disturbance and cold front will produce windy conditions, with
  High Wind Warnings in effect through this afternoon for wind
  prone locations of southeast Wyoming.

- Dry weather and above normal temperatures will occur through
  the week.

&&

.UPDATE...
Issued at 810 PM MDT Sat Oct 5 2024

No major changes with tonight`s update. Relative humidity values
increased to above Red Flag criteria and winds decreased across
much of the area, so the Red Flag Warning expired on time at
7pm. Additionally, the High Wind Warning expired on time at 6pm,
as winds decreased to well below High Wind Warning criteria.

&&

.SHORT TERM /THROUGH SUNDAY NIGHT/...
Issued at 1253 PM MDT Sat Oct 5 2024

Latest upper air analysis depicts the shortwave trough axis is
centered across the I-25 corridor in southeast Wyoming, with an
upper level ridge developing across the Pacific Northwest.
Observations throughout the morning have seen increased wind speeds
across the I-80 corridor, with wind gusts up to 68 mph recorded
across the North Snowy Range Foothills. Otherwise, gusty to stronger
winds will prevail outside of the current warnings, with speeds up
to 30 mph for both Cheyenne and Laramie.

Tonight into tomorrow should see a decrease in wind speeds with the
upper level ridge beginning to build eastward, with the upper
level closed low across the Canadian Border continuing to push
eastward into the Great Lakes by the nighttime hours and thus
easing the gradients across our zones. Generally milder
conditions expected through Monday morning, with the upper level
ridge centering across the Intermountain West and into the High
Plains. All in all, should be cooler by a few degrees into
tomorrow, with daytime highs in the mid-70s and overnight lows
in the mid 30s to high 40s. Starting to get temperatures where
frost could form tomorrow morning. However, will the lack of
moisture over the last few weeks, will be hard for frost to
form outside of sheltered areas. Will hold off on any frost
headlines during this forecast package.

Tomorrow evening will see a shortwave propagate within the flow
and dig across southeast Wyoming and into Northeast Colorado.
PWATs continue to show a lack of moisture advection into the
zone. As a result, will see some gusty winds return across
portions of the CWA, and continued dry conditions for the
remainder of the weekend.

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...
Issued at 256 AM MDT Sat Oct 5 2024

The upper level ridge is expected to continue to dominate the
forecast area through much of the week. This will result in
sunny and mild conditions through the week with mainly 10 to 20
mph wind speeds during the afternoon. However, the low
afternoon relative humidities will continue invoke near critical
fire weather conditions. Therefore, the threat for red flag
conditions still may exist periodically especially in the higher
terrain.

There is still a glimmer of hope for precipitation along with
cooler conditions this weekend. However, there is a lot of
discrepancy in the deterministic solutions on the large scale
upper level flow. The GFS is really getting excited about a
powerful closed low developing over the northern plains and
diving south into the central Plains. It even brings some hints
of a freeze to our forecast area with the potential for light
snow in the mountains. The ECMWF and GEFS are not as cold, but
they are picking up on a chance for light rain and is somewhat
in more agreement with 10/04 00Z GFS run. The NAEFS
precipitable water fields are showing about .5 inch which is
about 1 standard deviation above normal. This would indicate
there is a possibility for some light precipitation especially
in the mountains if we can cool and saturate the air mass with
orographics. Overall, there is some signs that a cool down may
take place on Saturday on Sunday, but not confident enough about
the precipitation potential at this time.

&&

.AVIATION /00Z TAFS THROUGH 00Z SUNDAY/...
Issued at 510 PM MDT Sat Oct 5 2024

Wind gusts will wind down quickly this evening, but increasing
coverage of FU/HZ from nearby wildfires in Western/Northern WY
will result in reduced VIS at times. Fluctuations to high-end
MVFR of 4 or 5 SM due to FU/HZ at times are possible this
evening, but overall expect VFR for all terminals for the
forecast period.

&&

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

&&

$$

UPDATE...AM
SHORT TERM...MRD
LONG TERM...REC
AVIATION...BW