Area Forecast Discussion
Issued by NWS Cheyenne, WY

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000
FXUS65 KCYS 122050
AFDCYS

Area Forecast Discussion
National Weather Service Cheyenne WY
150 PM MST Thu Jan 12 2017

.SHORT TERM...(This evening through Saturday Night)
Issued at 230 PM MST Thu Jan 12 2017

Forecast concerns in the short term deal with snow amounts tonight
into Friday.

Currently...Water vapor imagery showing a low circulation over
western Utah and southern Nevada this afternoon. Piece of energy
spun off this low moving northeast towards Carbon County. Mosaic
radar showing fairly widespread snow over western and northwestern
Colorado this afternoon and the area is moving towards the
northeast. Surface features showing a stationary front from
Evanston to Rawlins to Laramie south along the front range of
Colorado.

All short term guidance showing pretty good 6 hourly QPF over
southern Carbon County late this afternoon and particularly around
06Z tonight. 12Z ECMWF showing around .25 inches while NAM most
bullish with around .6 inches through the overnight hours. Getting
5-9 inches on forecast snow amounts for the Snowy and Sierra Madre
Ranges. Went ahead with a Snow Advisory for these two zones. Snow
looks to come to a quick end after 12Z Friday.

Another concern for tonight is fog. Persistent southeast flow
forecast at 850mb for areas along and east of the Laramie Range.
SOundings fairly favorable for fog. Did add areas of fog for
counties east of the Laramie Range and along the Platte River
Valley up to Douglas.

Certainly looks like the frontal boundary to our west gets edged
east through the day Friday. Westerly to southwesterly 700mb winds
return to southeast Wyoming. Outside of orographic mountain snow,
everybody else should be dry for the most part during the day.

.LONG TERM...(Sunday through Thursday)
Issued at 230 PM MST Thu Jan 12 2017

Sunday...Upper trough moves across eastern New Mexico and the Texas
Panhandle with lift across eastern Colorado and western Kansas and
perhaps a bit of lift into our far southeast counties, thus will
keep a slight chance of of rain and snow over our far southeast
counties south of a Cheyenne to Sidney line. Dry elsewhere. The
ECMWF is more north with the trough and QPF from the system into our
region, so still some uncertainty of the track.

Monday...The ECMWF is further north with the upper trough movement
taking the upper low to eastern Nebraska by late in the day, while
the GFS tracks the upper low to central Kansas. With still some
uncertainty, will continue to match with our neighbors, painting
some low POPS for our southeast third of counties, mainly earlier in
the day. With cloud cover and progged 700 mb temperatures, highs
from the mid 20s to mid 30s at lower elevations.

Tuesday...Slow warming and drying trend under northwest flow aloft,
though will likely see increasing middle and high clouds in advance
of the moisture approaching from the Pacific Northwest.

Wednesday...Warming trend continues based on thicknesses and progged
700 mb temperatures. Models differ somewhat with the ECMWF showing
southwest flow aloft and the GFS maintaining more ridging over the
western United States and northwest flow over our counties. In
either case, it looks dry, aside from a few mountain snow showers
over the Snowy and Sierra Madre Ranges.

Thursday...Similar temperatures to Wednesday based on thickness and
700 mb temperature progs as well as an increase in cloud cover.
Orographic snows likely to develop along and west of our Snowy and
Sierra Madre Ranges with moist southwest flow aloft ahead of the
next approaching shortwave.

&&

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1026 AM MST Thu Jan 12 2017

Wyoming TAFS...VFR early this afternoon, then becoming IFR and
MVFR by late afternoon and continuing most of the night, before
becoming VFR and MVFR after 11Z.

Nebraska TAFS...VFR this afternoon, then becoming IFR and MVFR
early this evening, then mostly VFR after 12Z except for IFR
at Scottsbluff.

&&

.FIRE WEATHER...
Issued at 230 PM MST Thu Jan 12 2017

Minimal fire weather concerns with existing snowpack and cold
temperatures/high humidities. Another system forecast to move into
the area this afternoon, bringing another round of widespread
snowfall for areas west of the Laramie Range.

&&

.CYS WATCHES/WARNINGS/ADVISORIES...
WY...Winter Weather Advisory from 5 PM this afternoon to 8 AM MST
     Friday for WYZ112-114.

NE...None.
&&

$$

SHORT TERM...GCC
LONG TERM...RUBIN
AVIATION...RUBIN
FIRE WEATHER...GCC



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