Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 250032

Area Forecast Discussion
National Weather Service Cheyenne WY
632 PM MDT Sun Sep 24 2017

.SHORT TERM...(This evening through Tuesday)
Issued at 259 PM MDT Sun Sep 24 2017

Tonight...Expect visibilities to slowly improve through the early
evening over the I-80 summit and foothills, thus have cancelled the
dense fog advisory, especially with rain expected to move into the
area overnight. A band of rain, with snow at mountain locations
expected to move across our counties of Wyoming this evening, so the
Winter Weather Advisory for the Snowy Range looks on track.
Precipitation chances should decrease somewhat after midnight in the
wake of the shortwave trough aloft passage. Still will see areas of
fog along and east of the Laramie Range with close temperature and
dewpoint spreads.

Monday...Upper trough still prevails overhead, though with some
clearing noted in the afternoon. Will likely see some scattered
showers develop in the afternoon with cool air aloft and adequate
low and mid level moisture. Warmer temperatures with somewhat less
cloud cover.

Monday night...Main trough aloft moves off to our east, though will
still likely see some cloud cover, with slow clearing from west to

Tuesday...Flow aloft turns westerly with more sunshine and
moderating temperatures. No signs of lift along with limited
moisture, thus dry. For high temperatures, compromised between the
NAM and GFS MOS maximums.

.LONG TERM...(Tuesday night through Saturday)
Issued at 259 PM MDT Sun Sep 24 2017

The models are in good agreement at showing an upper low developing
in the vicinity of Arizona on Tuesday night after splitting off from
the main upper level flow. This low is progged to lift northeastward
on Thursday to near western Colorado. The best moisture and lift
will remain mostly south into Colorado, however could see some
shower chances return to areas near the Colorado Border, especially
the Sierra Madre and Snowy Ranges. While temps will moderate by
the middle of next week, they will still remain a few days below
average. Winds will be weak through Friday in the split flow
aloft. Better warming may occur by next weekend as the shortwave
trough moves east of the region with stronger and more zonal flow
aloft over the Intermountain West.


.AVIATION...(For the 00Z TAFS through 00Z Monday evening)
Issued at 631 PM MDT Sun Sep 24 2017

Very poor aviation conditions to persist thru the period as low
clouds/fog blanket the area. IFR/LIFR will be common through at
least Monday morning, with perhaps some improvement after 18z
Monday. Mountain obscurations will persist across routes in
southeast WY thru the period as well. Band of precipitation
lifting across the area will bring a period of -SHRA to KLAR and
KCYS and to a lesser extent the western Nebraska Panhandle
terminals. In fact, confidence was not high enough to include more
that VCSH at Nebraska terminals. Precipitation will shift east by
sunrise Monday, with drying conditions anticipated thru the day on


Issued at 259 PM MDT Sun Sep 24 2017

No concerns based on projected winds and humidities.


WY...Winter Weather Advisory until midnight MDT tonight for WYZ114.




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