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Area forecast discussion 
National Weather Service Denver/Boulder Colorado
523 am MST sun Dec 21 2014

Short term...(today through tonight )
issued at 523 am MST sun Dec 21 2014

Moisture plume moving into Colorado this morning on the nose of a
very strong jet. For this morning there is weak warm advection and
increasing winds...with deepening moisture but with some middle level
stability. This should generate steady snow over and west of the
Front Range...but not heavy yet. This afternoon the lift will
increase a bit and cold advection will set in making for a much
more productive environment this evening. It looks like the best
lift...strongest winds...and best instability will be over the
Interstate 70 corridor in the late afternoon and evening. Bad
timing for the impact could be substantial. We will
be hitting this message hard today. Winds go more northerly later
tonight with the best lift sinking south...but still reasonably
good conditions for moderate to heavy snow the rest of the night.
Current highlights look alright...tweaked the timing of the snow a
bit to hit this evening the hardest. This may be a candidate for a
Blizzard Warning later today if it pans out.

For areas east of The Divide...downslope winds but plenty of snow
spilling over into the foothills. In addition some forcing with
the jet so we will need some accumulations in the higher foothills
and South Park at the height of the event. Some threat of high
winds...though not enough for a warning. High winds appear likely
for the higher mountain areas that are in the Winter Storm
Warning...such as Berthoud Pass...Niwot Ridge and other above
timberline areas sticking up into the jet. For the more populated
foothill areas gusts in the 50-70 miles per hour range look likely tonight.
Jet related banding may be strong enough to overcome the downslope
at some point...especially later tonight as the deep wind
component becomes more northerly and there could be some low level
convergence somewhere on the east side. Probably a better chance
further away from the mountains...but some threat in Denver as
well. This stuff will probably be light but with the strength of
the jet and some instability there could be some places that get a
couple of inches as a shower band comes over.

Boosted high temperatures a couple of degrees today...warm airmass
and windy.

Long term...(monday through saturday)
issued at 523 am MST sun Dec 21 2014

There is northwesterly flow aloft for the forecast area on Monday.
The flow aloft becomes almost due northerly by 12z Tuesday morning
with jet level speeds on the increase. The flow aloft is northerly
around 100 knots Tuesday and Tuesday night. Downward synoptic
scale energy is prognosticated over the County Warning Area all four periods...Monday
through Tuesday night. The boundary layer flow is all northwesterly
for the County Warning Area Monday through Tuesday. Concerning stays
fairly deep over the mountains Monday and Monday night. By Tuesday
..moisture is decreasing in the high country. But not totally
gone until Tuesday evening. For the is pretty dry
Monday morning...then moisture increases in the middle and upper
levels...lowering...especially over the eastern half by Monday
evening continuing into Tuesday. All areas are pretty dry Tuesday
night. The quantitative precipitation forecast fields have pretty decent amounts prognosticated in the
mountains Monday...decreasing Monday night. There is little to no
measurable precipitation prognosticated for the plains Monday...but a tad
for Monday night into Tuesday morning. So for probability of precipitation...the
highlights are out and we are expecting a healthy snowfall for
the mountains. Widespread snow and some blowing snow too are
expected in the mountains Monday into Monday evening before
decreasing into Tuesday. Plains probability of precipitation will be 0-30%s Monday into
midday Tuesday. Temperatures on Monday are prognosticated to be 6-10 c
colder than today's highs. Tuesday is another 1-4 c cooler than
Monday for highs. For the later days...Wednesday through Saturday
..models have strong northerly flow aloft on Wednesday with upper
ridging to move over the County Warning Area through Wednesday night. Then a
broad upper trough moves in Thursday into Friday night. The flow
aloft is west-northwesterly and moderate in speed. On Saturday
strong north-northwesterly flow aloft is prognosticated. The European model (ecmwf) has
better parameters overall for snow Thursday into Friday...
especially in the mountains.


Aviation...(for the tafs through 12z Monday morning)
issued at 523 am MST sun Dec 21 2014

VFR today. West winds will mix down between 18z and 21z with gusts
in the 20 to 30 knot range...which could cause crosswind issues at
kden/kapa. Gusts as high as 40 knots and low level wind shear possible at kbjc
where the strongest winds will likely be from time to time during
the late afternoon and evening. After 08z winds will become more
northerly and scattered snow showers are expected...possibly
causing localized IFR conditions.


Bou watches/warnings/advisories...
Winter Storm Warning from noon today to midnight MST Monday
night for coz031>034.

Winter Weather Advisory from noon today to midnight MST Monday
night for coz030.



Short term...gimmestad
long term...rjk

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