Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 232204

Area Forecast Discussion
National Weather Service Cheyenne WY
304 PM MST Tue Jan 23 2018

.SHORT TERM...(Tonight - Wednesday Night)
Issued at 233 PM MST Tue Jan 23 2018

It is a challenging and low-confidence wind forecast for tonight &
Wednesday AM in the ARL/BRX areas. A semi-favorable pattern should
set up over the next 12 hours with pressure falls spreading across
central MT into eastern WY. This is expected to result in a fairly
substantial H85 CAG-CPR gradient near 65 meters between 9z-15z Wed
AM. The models also show an uptick in H7-H8 flow as this occurs w/
widespread 45-50 knots over the wind corridors, strongest over the
BRX area. Guidance has been trending slightly weaker though. There
are a few concerns that could limit high wind potential as we head
into the early morning hours. First, the upper-level short wave is
rather weak, and upper-level ridging dominates. This yields a very
stout subsidence inversion tonight per GFS soundings, which may be
too strong to overcome w/out the presence of a stronger wave. Also
some concerns that the low-level gradient around ARL could be more
W-E rather than a more favorable SW-NE. Over BRX, confidence still
low on the position of the surface trough. Based on this reasoning
we decided to maintain the High Wind Watch, and let the next shift
decide if a warning is warranted. Believe both ARL and BRX will be
close to criteria around 12z Wed or so.

Another potential high wind episode on Wed night/Thu as a vigorous
short-wave tracks across the western US. Strong southwesterly flow
aloft and decent subsidence w/ the upper jet may support high wind
in the wind corridors once again. Did not reflect this in the High
Wind Watch product for Arlington/Bordeaux, but we did go ahead and
add the Ferris/Seminoe mountains in northern Carbon county.

.LONG TERM...(Thursday through Monday)
Issued at 233 PM MST Tue Jan 23 2018

Strong winds linger into Thursday afternoon. A weakening mid-level
short wave is progged to sweep across the area Friday, potentially
resulting in some mountain snow showers. Otherwise, expect most of
the area to be dry. A generally quiet pattern is likely to prevail
through the remainder of the extended forecast period.


.AVIATION...(For the 18Z TAFS through 18Z Wednesday morning)
Issued at 1131 AM MST Tue Jan 23 2018

VFR conditions will prevail through the period.


Issued at 330 AM MST Tue Jan 23 2018

Despite periods of gusty winds, overall fire weather concerns will
remain low with recent snow pack.


WY...High Wind Watch from Wednesday evening through Thursday
     afternoon for WYZ104.

     High Wind Watch from midnight MST tonight through Wednesday
     afternoon for WYZ106-110.



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