Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 021038

Area Forecast Discussion
National Weather Service Denver/Boulder CO
338 AM MST Fri Dec 2 2016

.SHORT TERM...(Today and tonight)
Issued at 220 AM MST Fri Dec 2 2016

Weak upper level system over Great Basin will continue to develop
and dig into southern Arizona by later today. Colorado will be
only under under weak QG ascent through this evening...mainly
focusing on the mountains. Orographic flow will also be very weak
and only shallow moisture depth. These factors will result in only
light snowfall amounts, mainly 1-2 inches in the mountains. There
still look to be some light flurries or light snow over the
foothills and adjacent plains but low level flow will generally be
southeast. Little if any accumulations expected on the plains
mainly a dusting to a 1/4 inch. Further east on the plains no snow
expected as eastern areas removed from any dynamical support.
Given satellite imagery, best chances of snow will be from late
this morning through early evening hours.

Temperatures will be cooler today, with forecast soundings only
support 30s to around 40 over the far northeast plains.  The
northern branch of the trof will sweep across Colorado later
tonight with drier airmass and northwest flow. Light snow and
clouds will diminish by late evening through overnight. Only minor
changes to the current ongoing forecast.

.LONG TERM...(Saturday through Thursday)
Issued at 220 AM MST Fri Dec 2 2016

Drier air in nw flow aloft will spread across the area on Sat and
then become more wly on Sun.  A sfc lee trough will dvlp over nern
CO on Sat and then strengthen on Sun.  Overall it should be dry thru
the weekend with moderating temps.  Highs on Sat will rise into the
lower to mid 40`s over nern CO and then range from 45 to 50 on

For Sun night into Mon wly flow aloft will strengthen with moisture
gradually increasing in the mtns.  Lapse rates will gradually
improve by Mon aftn and combined with favorable orographics should
see a good chc of snow in the mtns.  Over nern CO it will remain dry
with highs fm 45 to 50.

Meanwhile big changes are still expected Mon night thru Tue as an
upper level trough moves into the area along with a stg cdfnt. The
GFS has deepening upslope flow late Mon night into Tue behind the
fnt along with increasing mid lvl ascent.  This would lead to a good
chc of snow east of the divide across the plains.  However the ECMWF
is slower with the passage of the upper level trough and keeps best
mid lvl ascent Tue aftn thru Tue night.  Thus there are some timing
issues as to when the best chc of snow would be fm the foothills
across the plains.  In the mtns there will be a good chc of snow as
well.  Highs on Tue will only be in the 20`s across nern CO behind
the first cdfnt.

For Tue night into Wed the GFS has the upper level trough moving
east of the area with drier air spreading across with snow ending
Tue evening.  Meanwhile the ECMWF doesn`t show the main upper level
trough exiting the area until midday Wed with favorable mid lvl
ascent and upslope flow lasting thru Wed morning.  Thus snow chances
would linger Tue night into Wed morning if the ECMWF verifies. At
this point will leave in a chc of snow across the area Tue night
with a slight chc on Wed until it becomes more clear how things
will evolve. Meanwhile temps will be even colder on Wed as a
second surge of colder air moves into the area. Latest 850-700 mb
temps would only support highs in the teens across nern CO.

By Wed night into Thu the GFS has nwly flow aloft across the area
with some moisture embedded in the flow which would lead to a chc of
snow in the mtns.  Across the nern CO it would be dry with highs in
the 20s.  Meanwhile the ECMWf has a secondary upper level trough
moving across the area with another shot of reinforcing cold air.
This would lead to a chance of snow in the mtns with possibly a chc
of light snow in and nr the foothills.  In addition highs over nern
CO would likely stay in the teens based on the ECMWF solution.


.AVIATION...(For the 12Z TAFS through 12Z Saturday morning)
Issued at 220 AM MST Fri Dec 2 2016

mid level deck of clouds over local terminals now, and then some
gradual lowering of ceilings expected by later this morning as
flurries/very light snow develop. Could see some ILS approaches by
late am as cigs expected to drop between 5000-6000ft agl and then
possible CIGS down to 3000 ft agl between 22z-02z. Clouds and
light snow will decrease this evening with clearing skies
overnight. Any snow accumulation will be under a quarter inch or




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