Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 111147

Area Forecast Discussion
National Weather Service Cheyenne WY
447 AM MST Wed Dec 11 2019

.SHORT TERM...(Today and tonight)
Issued at 258 AM MST Wed Dec 11 2019

Latest nighttime microphysics satellite imagery shows areas of
high clouds moving southeastward across the area with fairly
quite conditions expected through the remainder of the morning.
These high clouds are ahead of an approaching shortwave trough
that will give rise to snowfall over the southern mountains
particularly late this afternoon through the evening. Winter Storm
Watch in effect for the Sierra Madre and Snowy Ranges given the
fairly consistent agreement of models of over half inch of QPF for
heavy snow totals through Friday morning.

Winds have remained generally breezy but under high wind criteria
this evening though 850mb gradients remain fairly elevated for
KBRX through today with KCPR increasing above 50 meters after 12z.
High Wind Warning remains in effect with gusts up to 65 mph still

Seasonably warm temperatures in the mid to upper 40s over the high
plains expected today with initial sunny skies with increasing
clouds through the afternoon ahead of the shortwave.

.LONG TERM...(Thursday through Tuesday)
Issued at 258 AM MST Wed Dec 11 2019

In the wake of the shortwave trough flow aloft becomes much more
favorable with increased jet stream speeds to keep concerns for
Friday of yet another high wind event particularly across the gap
wind areas with height gradients in the upper 60 and 70 meter
ranges for the Craig to Casper and Bordeaux line respectively.
High Wind Watch likely will be needed but avoided implementing
this forecast cycle to avoid confusion with ongoing High Wind

Isolated heavy snow bands to continue mainly across the Snowy and
Sierra Madre Ranges with expected higher accumulations there.
Scattered light snow possible across the remainder of the CWA
though accumulations at this point through Saturday afternoon
remain generally under an inch outside of the southern mountains.

With sharp northwest flow, colder air expected to be advected in
with the trough digging into the region with near normal highs in
the low 30s for the weekend.

Moisture tap dries up into Monday with lingering flakes and
flurries ending west to east as zonal ridging builds in through


.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 445 AM MST Wed Dec 11 2019

VFR conditions expected through the forecast period for area
terminals. Upper level clouds have begun moving overhead from the
northwest early this morning. Additionally, low level clouds
northeast of the CWA with ceilings 1 to 5 kft have been pushing
west towards KCDR most of the night per GOES Nighttime
Microphysics imagery. Model guidance does not bring restricting
flight conditions into KCDR, but will continue to monitor
satellite trends over the next few hours. Otherwise, main concern
Wednesday will be gusty west winds across SE WY terminals
beginning mid-morning. LLWS may be a concern Wednesday night,
mainly for KCYS and KLAR as 45-50 kt jet develops just off the
surface with the tightening height gradients.


Issued at 257 AM MST Wed Dec 11 2019

Windy stretch across the gap areas in SE WY continue over the
next couple days with a return to mountain snowfall over the
southern mountains ranges starting late this afternoon with
periods of snowfall continuing through the weekend. Lighter
accumulations of generally under an inch expected elsewhere mainly
between Friday afternoon and Saturday afternoon. RH values remain
above critical thresholds.


WY...Winter Storm Watch from this afternoon through Friday morning
     for WYZ112-114.

     High Wind Warning until 5 PM MST this afternoon for WYZ106-110.



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