Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 021749
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1049 AM MST Fri Dec 2 2016

.UPDATE...
Issued at 1040 AM MST Fri Dec 2 2016

Light snow falling over the foothills and portions of Boulder and
Larimer counties due to the influence of some local dynamics and
light upslope flow. Do not expect much in accumulation due to
limited moisture and the lack of deep upslope along the Foothills.
Have increased pops for those areas and continued it through the
afternoon. Do not expect temperatures to increase too much with
cloud cover increasing to will drop highs a few degrees for areas
closer to the foothills.

&&

.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
Sun.

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 orographic 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 18Z TAFS through 18Z Saturday afternoon)
Issued at 1040 AM MST Fri Dec 2 2016

Mid level cloud deck firmly entrenched over area aiports with low
clouds moving in by 19 to 20z with the onset of flurries. Expect
some light snow between 23 and 03z with increasing ESE winds. ILS
approaches possible with the onset of snow and covered by a TEMPO.
By 03z subsidence and clearing will move in with winds veering
around to drainage by 14z. Winds will remain light through the
period. Any snow accumulations at area airports will be under a
quarter of an inch. Temperatures will be cooler with highs
hovering around 30.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

UPDATE...Bowen
SHORT TERM...Entrekin
LONG TERM...RPK
AVIATION...Bowen



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