Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 171144

Area Forecast Discussion
National Weather Service Cheyenne WY
541 AM MDT Fri Aug 17 2018

.SHORT TERM...(Today and tonight)
Issued at 223 AM MDT Fri Aug 17 2018

Some morning lower cloud ceilings and patchy fog are possible
across SE WY and the NE Panhandle. Fog is not expected to become
as dense as many locations entered the overnight with
temperature/dewpoint spreads greater than 10 degrees Fahrenheit.
The better chances for fog will be in the far eastern NE Panhandle
counties in the forecast area. Some locations could get down to a
few miles in visibilities with dissipation expected around 9 AM

An upper level ridge will continue to build across the region as
the first set of a series of shortwaves impact the area over the
weekend. Low level moisture of around half an inch will be
sufficient for initial shower and thunderstorm development mainly
along the Snowy and southern Laramie Range over the mountains
before moving off into the high plains in the afternoon to early
evening. Daytime highs will be seasonal with low to mid 80s
across the high plains with some pockets reaching 89 degrees,
cooler in the mountains with highs in the upper 60s to lower 70s.

.LONG TERM...(Saturday through Thursday)
Issued at 223 AM MDT Fri Aug 17 2018

A more potent shortwave trough with an associated cold front will
pass through the region on Saturday with additional moisture and
forcing for widespread showers and thunderstorms. Better chances
for higher precipitation amounts will be localized in the NE
Panhandle though up to a tenth of an inch for the WY high plains.
Frontal passage will be during the afternoon making for a cooler
overnight with lows in the upper 40s to mid 50s. Sunday highs will
also be on the cooler side in the upper 60s and low 70s with
continued chances for showers through the day from leftover
moisture and instability. Precipitation will be out of the region
Sunday night as an upper level ridge builds into the region.

GFS and EURO model showing a quick low level shortwave moving into
the region Monday afternoon into Tuesday for another round of
showers and thunderstorms. Tuesday afternoon may have some
isolated storms as high amplitude ridging takes hold aloft before
monsoonal moisture advects into the region on Wednesday for
showers along the Colorado border along the Snowy and southern
Laramie Range. Ridging overall will bring temperatures back their
seasonal averages in the lower to mid 80s across the high plains.


.AVIATION...(For the 12Z TAFS through 12Z Saturday morning)
Issued at 540 AM MDT Fri Aug 17 2018

Patchy MVFR in mist/fog will be possible from the eastern WY plains
into the western NE Panhandle thru 15Z, with VCFG at KAIA and KSNY.
Otherwise, VFR will prevail through tonight. Widely scattered
convection will affect all but KRWL. It will be breezy with
southerly winds occasionally gusting to 20 kt.


Issued at 223 AM MDT Fri Aug 17 2018

A weak shortwave trough will move overhead the region Friday
afternoon with some additional moisture and forcing that could
initiate showers and convection over the mountainous areas with
later afternoon and evening convection moving off into the high
plains. Winds will still remain generally light with gusts into the
middle to upper teens on Friday. Lowest RH values in the middle
teens will be constrained to the western portion of Carbon County. A
more potent shortwave with an associated cold front will move across
the area Saturday afternoon bringing a better chance for overhead
showers and thunderstorms with RHs in the upper 20s to middle 40s
across the region.




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