Area Forecast Discussion
Issued by NWS Cheyenne, WY

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FXUS65 KCYS 112015

Area Forecast Discussion
National Weather Service Cheyenne WY
115 PM MST Wed Jan 11 2017

.SHORT TERM...(This evening through Thursday night)
Issued at 115 PM MST Wed Jan 11 2017

Have seen some pretty impressive snow rates over the Sierra Madre
and Snowy Ranges through the morning with some locations in the
Sierra Madre getting 0.2-0.3 inches of SWE per hour. Moderate to
heavy snow is currently falling in the Arlington area, however it
looks like the back edge of the precip shield is over western
Carbon county as it has stopped snowing in Rawlins. The models
continue to indicate the snow tapering off by the late aftn over
lower elevations. Winds should begin to rise in the Arlington and
Elk Mountain areas by later this aftn and into the evening with
the 850 mb CAG-CPR gradient increasing to around 55 meters and the
sfc trough just to the northeast. Thus, with the fresh snow on
the ground and strong winds developing, expect significant blowing
snow through the evening even as the falling snow ends. Went ahead
and issued a Winter Storm Warning through 12Z Thurs for the
Arlington zone with this reasoning. Orographic snow over the
western mtns should largely taper off by late tonight.

Not as active through the remainder of the short term. The front
that has stalled along the Laramie Range will return slightly to
the northeast this evening before moving back southward over the
region by Thursday morning. Upper trough amplifies into central CA
during the day on Thursday. Upper lvl divergence will combine with
moist southwesterly flow aloft to bring snow chances back to the
Sierra Madre and Snowy Ranges by Thurs aftn and then spreading
over portions of southeast WY during the evening. Overall, looks
like a light snow accumulations over lower elevations with 4-8
inches in the mtns.

.LONG TERM...(Friday through Wednesday)
Issued at 115 PM MST Wed Jan 11 2017

Long term looks pretty tranquil from what is being seen in the
medium range models.

Starting off Friday, system departing to the east with snow
ending. Looks like the mountains will be the last to end. 700mb
winds fairly weak, so we may get a break for a while.

Fairly dry through the weekend as a broad upper ridge remains over
the area. Continued light winds at 700mb. Temperatures at 700mbs
range from -3 to -5C, so not overly cold. Should see highs in the
mid 30s east of the Laramie Range and mid 20s to low 30s west.

Next chance for snow may be Monday along the Colorado/Wyoming
border. Both the GFS and ECMWF now have the southern low that we
have been watching ejecting out into Kansas Monday instead of
moving northeast into Nebraska. With this solution, most everyone
should stay dry.

Better chances Wednesday next week as next Pacific shortwave moves
into western Wyoming. This may be a wind maker more than a snow
producer. Will have to wait and see what this system does as we
get closer.


.AVIATION...(For the 18Z TAFS through 18Z Thursday afternoon)
Issued at 1031 AM MST Wed Jan 11 2017

Tough forecast for the 18Z TAFs for southeast Wyoming and Nebraska
Panhandle. Guidance showing front retreating northeast this
afternoon into the northern Panhandle and eventually into South
Dakota this evening. Do feel the HRRR and other guidance may be
too fast on doing this, especially for KCYS where we are
experiencing northeast winds now when guidance is forecasting
west winds. So, confidence is low for this set of TAFs. Snow fills
in for KLAR, so do feel confident on KLAR going down. Generally
followed the HRRR guidance with low confidence.


Issued at 115 PM MST Wed Jan 11 2017

No fire weather concerns through the week. Temperatures will
remain cold with minimum afternoon humidity values generally above
40 percent.


WY...Winter Storm Warning until 5 AM MST Thursday for WYZ110-112-114.

     Winter Weather Advisory until 5 PM MST this afternoon for WYZ109-



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