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Area forecast discussion...updated 
National Weather Service Cheyenne Wyoming
1122 am MST Friday Jan 30 2015

Short term...(today through sunday)
issued at 229 am MST Friday Jan 30 2015

Today...despite broken to overcast skies over Carbon County...we
may see some areas of fog there with temperature and dewpoint
spreads around 3 degrees. Will see increasing middle and high
clouds ahead of the shortwave trough aloft approaching from
southern Arizona...with a few snow showers over our snowy and
Sierra Madre ranges...dry elsewhere.

Tonight...areas of fog will increase in coverage as the low levels
saturate...though the fog coverage will be limited somewhat by
the amount of middle and high level clouds. With some weak
shortwave trough aloft energy...upslope and saturated low
levels...expect a chance of snow south of a Rawlins to Cheyenne
line. fast moving shortwave trough Alberta
type clipper...will move to northeast Wyoming sending the next
Arctic cold front south across our northern counties. Enough low
and middle level moisture...northerly upslope and weak upward
vertical motion to produce a chance of light snow south of a
Rawlins to Scottsbluff line.

Saturday night...strong cold air advection and cyclonic flow aloft
will wring out a chance of light snow but with minimal accumulations
due to lack of low and middle level moisture.

Sunday...breezy and cold day with fast north northwest flow aloft
and decent cold air advection continuing. High temperatures will
struggle to reach freezing at most locations despite some

Long term...(sunday night through thursday)
issued at 229 am MST Friday Jan 30 2015

An upper level ridge will build over The Rockies Sunday night into
Monday with strong warm air advection occurring over the County Warning Area through this time.
Looking at temperatures spiking into the 40s and 50s for Monday. Shortwave
energy on the nose of a 100 knots jet will move quickly atop the
ridge and over The Rockies as well and the leeside pressure trough
will rapidly deepen in advance of this wave. Models show winds in
the 800-700 mb layer over southeast Wyoming increasing to 50+ kts
late Sunday night as the low level pressure gradient strengthens. With
warm air advection in place...likely to see strong winds become trapped near the
surface in the wind prone areas of southeast Wyoming. Upslope flow
along the western slopes will strengthen as these winds develop
and will combine with increased Pacific moisture to bring a good
chance for orographic snow during this time as well. The low level
pressure gradient will relax slightly on Monday evening as the
initial wave shifts east...but another and somewhat stronger vorticity
maximum will move into the northern rockies Monday night and will
reintensify the gradient. Still thinking the wind prone areas will
see a second round of high winds while orographic snow intensifies
over the mountains Monday night through Tuesday morning. High
winds could expand further east onto the plains late Tuesday
morning with nearly 60 kts prognosticated at 750 mb and only patchy
cirrus overhead to potentially inhibit mixing. Cant rule out a few
showers mainly over the northern zones from Converse to Box Butte
counties Tuesday morning as the vorticity moves across the northern
rockies and an associated cold front stalls over this area.

Beyond Tuesday...confidence is low whether high winds will be
realized in the wind prone areas once again Wednesday
morning...or if the cold front will move south through the plains
early enough to shut off the high winds and bring rain/snow to
the County Warning Area instead. The 00z and Gem all show varied
solutions with the southward surge of the front...with the Gem
nearly 12hrs faster than the GFS...and the ec 6hrs slower than the
GFS. With this level of variability on timing...will trend toward
a middle ground solution for now which means windy conditions will
prevail through Wednesday morning but will not quite reach high
wind levels. Will keep mainly slight chance probability of precipitation Tuesday night
into Wednesday morning for much of the County Warning Area except in the
mountains where chance probability of precipitation are reasonable. Mostly dry conditions
and less wind will prevail for Thursday.


Aviation...(for the 18z tafs through 18z Saturday afternoon)
issued at 1114 am MST Friday Jan 30 2015

Currently getting MVFR category observed at Rawlins Wyoming where light
snow showers are producing visibilities down to 2sm...but that should
not be a prevailing condition through the afternoon with MVFR
ceilings broken 2000ft above ground level expected. Otherwise rest of forecast area
expected to see VFR conditions through the evening with lowering
ceilings to MVFR across the Alliance and Sidney NE areas later
tonight with light southerly flow. May get some patchy fog in
spots tonight (particularly where any light upslow develops). Will
also see a chance of light snow with MVFR category conditions
possible Rawlins and Laramie closer to where oragraphically
induced snow showers in the mountains are expected...but otherwise
no major concerns through tomorrow morning and we dont expect to
see prevailing reduced visibilities due to snow for those
locations through morning. The higher snow chances through morning
are expected to be to our south in the Colorado mountains.


Fire weather...
issued at 229 am MST Friday Jan 30 2015

Minimal concerns. A strong Arctic cold front will sweep quickly
north to south across the district on Saturday...ushering in
colder temperatures for Sunday. Warming temperatures for Monday
and Tuesday before another cold front brings cooler temperatures
for Wednesday.


Cys watches/warnings/advisories...


Short term...Rubin
long term...rjm
fire weather...Rubin

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