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Area forecast discussion 
National Weather Service Cheyenne Wyoming
240 am MST Wednesday Nov 25 2015

Short term...(today through Thursday night)
issued at 330 am MST Wednesday Nov 25 2015

Forecast challenges deal with snow amounts and timing.
Currently...a cold front lays roughly along a line from Lusk to
Evanston early this morning. Temperatures up in Montana this
morning are in the single digits and low/middle teens. Quite windy up
there as well with most metars reporting gusts in the upper 20kt
range. Quite mild here south of the front with upper 20s and low
30s being reported.

Front moves through the Cheyenne area by sunrise. Should see
falling temperatures through the day as 700mb temperatures fall
from 0c this morning to -10c by this afternoon.

Snow looks to begin in earnest this evening after 00z today. Both
the GFS and European model (ecmwf) show an upper trough moving into southwest
Wyoming at that time with northern Carbon and western Converse
counties seeing the first snow. By 06z tonight...central
Wyoming...including northern Carbon and Converse counties should
see widespread moderate snow. GFS 700mb winds increase to 30kts
after 06z and temperatures falling into the upper single digits
and low teens. Should see some pretty high snow ratios with these
cold temperatures...on the order of 20:1 to 25:1. Getting roughly
a .4 to a half inch of quantitative precipitation forecast off the GFS. Slightly less from the
European model (ecmwf) and NAM...but still .25 to .35 inches. With 20:1
ratios...getting snow amounts on the order of 7 inches for Rawlins
and Douglas. Went ahead and upgraded winter headlines to warnings
for areas out west tonight into Thanksgiving day.

Surface high builds into the area Thursday night. 850mb
temperatures down to -12c. With clearing skies and light
winds...looking at probably our coldest temperatures of the season
so far. Have low single digits in the forecast...that may be too

Long term...(friday through tuesday)
issued at 330 am MST Wednesday Nov 25 2015

Friday...cold upper trough continues to remain nearly stationary
over southern Nevada with cold surface high pressure entrenched over
our counties. Slight chance of light snow over the southern half of
our counties with adequate low and middle level moisture and weak
upward vertical motion primarily due to upslope. Continued quite
cold with fresh snowpack...700 mb temperatures near -11 celsius and
cloud cover. lobe of the upper low rotates across eastern Wyoming
producing a few snow showers. Continued cold per prognosticated 700 mb cover and snowpack.

Sunday...upper trough lifts into the northern rockies and northern
plains states with our flow aloft turning southwest helping for a
slight warming trend. Still though enough residual cloud cover and
orographics for scattered snow showers over our snowy and Sierra
Madre ranges...dry elsewhere.

Monday...pesky upper trough rotates across either the
per the GFS...or over Nebraska...per the European model (ecmwf). In either
case...cold temperatures aloft will promote at least isolated snow
showers over our counties with temperatures remaining quite
cold...and perhaps even colder than our current forecast indicates.

Tuesday...finally...a return to slightly warmer weather as the flow
aloft backs to west or northwest allowing surface Lee troughing to
strengthen and helping a moderation in the cold airmass.


Aviation...(for the 12z tafs through 12z Thursday morning)
issued at 1024 PM MST Tuesday Nov 24 2015

Wyoming tafs...VFR prevails with an Arctic cold frontal passage
this morning with ceilings lowering in the afternoon to MVFR and
then to IFR in snow during the late afternoon and early evening.

Nebraska tafs...ceilings and visibilities lowering today in the
wake of an Arctic cold frontal passage with IFR developing during
the day from north to south and snow and fog developing early
Wednesday evening.


Fire weather...
issued at 330 am MST Wednesday Nov 25 2015

Cold front moving through the area this morning. Areas of snow
developing behind the front with widespread accumulating snow
likely this evening into Thursday. Fire weather conditions minimal
with snow and cold temperatures.


Cys watches/warnings/advisories...
Wyoming...Winter Storm Warning from 9 PM this evening to 5 PM MST Thursday
for wyz101-103>105-109-110-114.

Winter Weather Advisory from 11 PM this evening to 5 PM MST
Thursday for wyz102-106-107-111>113-115>118.



Short term...gcc
long term...Rubin
fire weather...gcc

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