Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 202045
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
245 PM MDT Thu Apr 20 2017

.SHORT TERM...(Tonight through Saturday)
Issued at 223 PM MDT Thu Apr 20 2017

Clouds increasing over the CWA this afternoon with showers also
increasing gradually over and near the higher mtns. This in
response to digging upper shortwave now over the Pacific
northwest. This system will continue to drop southeast overnight
and close off an upper low over Colorado during the day Friday.
Rains and higher elevation snow will increase across mainly the
southwest half of the CWA overnight and continue across most of
the CWA Friday before tapering off Friday night. Main difficulty
will continue to be the level of accumulating snow later tonight
into Friday. Still appears that will be generally above about
7000 feet so current Winter Wx Advy looks good overall though the
start of the snow over the South Laramie Range may hold off until
later this evening. Some snow likely to fall as well later tonight
into Friday morning down to around 6000 feet or so but initial warm
ground and Sun angle likely to limit accumulations late tonight
and Friday. Winds modest and should not create much of a problem.
Much cooler over much of the CWA Friday given clouds and pcpn with
chilly conditions Friday night. System pulls away Friday night
and saturday allowing for warmer weather to begin its return on
Saturday.

.LONG TERM...(Saturday night through Thursday)
Issued at 223 PM MDT Thu Apr 20 2017

A warm and dry start to the extended forecast period w/broad upper
level ridging in place. Strong subsidence beneath the ridge should
preclude any risk for precipitation through Sunday evening. Expect
highs in the 60s and 70s with H7 temperatures of +5 to +7 C. GFS &
ECMWF both suggest a fast moving short-wave trough tracking across
the central Rockies on Sunday night/Monday. Jet energy is expected
to be fairly modest, but 700-300 hpa RH progs show sufficient mid/
high level moisture for scattered precipitation coverage. It looks
like the overall pattern will remain rather unsettled through much
of next week with numerous waves embedded w/in fast WNW flow aloft
through Thursday. Medium range models suggest a deepening low over
the western US mid to late week, which could have the potential to
bring widespread precipitation to the CWA.

&&

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1151 AM MDT Thu Apr 20 2017

VFR conditions should prevail across much of southeast Wyoming and
the western Nebraska Panhandle through this afternoon, although we
expect rain showers to begin developing roughly along and south of
I-80 from KRWL to KCYS as early as 20z today. Ceilings will likely
lower through the afternoon/evening with a good potential for LIFR
or IFR conditions at KCYS/KLAR after 03z Fri. After 09z, pcpn will
become heavier and more widespread, especially between Laramie, WY
and Kimball, NE. A changeover to snow is expected at elevations at
or above about 6000 feet, so there is a risk for accumulating snow
at KCYS early in the AM with visibilities possibly reduced to one-
half mile. In the Nebraska Panhandle, precipitation will likely be
rain and overall aviation impacts should be lower. However, expect
MVFR to locally IFR ceilings to spread northeast across the region
between 12z-18z Friday.


&&

.FIRE WEATHER...
Issued at 223 PM MDT Thu Apr 20 2017

Wetting pcpn expected across much of the area tonight and Friday
with cooler temperatures. This will keep fire weather concerns nil
through at least the weekend.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...Winter Weather Advisory from 6 PM this evening to 6 PM MDT
     Friday for WYZ112-114-116.

NE...None.
&&

$$

SHORT TERM...RE
LONG TERM...CLH
AVIATION...CLH
FIRE WEATHER...RE


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