Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Denver/Boulder Colorado
324 am MST Friday Mar 7 2014
Short term...complex storm system will move across Colorado today
and tonight with main concern snow potential over mountains and
adjacent plains. The storm is a bit deeper and stronger than
previous forecast. The evolving precipitation has been slow to evolve
but radar imagery showing some heavier snowfall now developing
over western Colorado. This heavier snowfall will shift eastward
into the north central mountains this morning. In the
meantime...surface low continues to deepen over southeast Colorado
as high pressure builds southward from Montana. Weak pressure
rises moving into northern Colorado but not a huge cold front to
really lower temperatures quickly. Main issue over the plains
will be the rain/snow line as temperatures will be in the upper
30s to middle 40s this morning. Expect much of this precipitation to be rain
this am and then become a more mix of rain/snow this afternoon.
More complicated towards the Front Range as expect heavier showers
may turn precipitation to all snow at least for a short term this
afternoon. Forecast soundings are fairly unstable with steep lapse
rates and this looks reasonable based on the lightning strikes
reported across Utah overnight.
The short range models have become more bullish with the quantitative precipitation forecast and
snowfall with quantitative precipitation forecast on the plains from a quarter to a half inch and
upwards of an inch of liquid over higher east slopes. This may
result in upwards of a foot or more of snow in the higher
foothills and along The Divide. Could see 2-3" of snow per hour
with the heavier snowfall given the lapse rates and moderate qg
ascent. Even the dry NAM model from 24 hours ago is now the most
excited about heavy snowfall. Most of the models now have
consistency about significant quantitative precipitation forecast with this system.
As for the hilites have upgraded or added the Front Range foothills
and zones 33..34 to winter storm warnings today and tonight and
added advisories for zones 37..41. Have also added the Boulder and
Denver area into an advisory for later this afternoon and tonight.
Amounts be more marginal but the time of heaviest precipitation may
coincide with the late day rush hour and could present a problem.
For the urban corridor looks like 2-6"...heaviest near the
foothills. Lesser amounts further north and east...away for the
best upwards forcing. Snowfall will gradually end from north to
south later tonight with gradualy clearing.
Long term...some light snow may still exist over the foothills
and Palmer Divide early Saturday morning before drying and
downward qg motion pushes it south. Clearing skies will allow sun
to shine...however temperatures should not climb too much under
the Post frontal airmass. Expect readings in the middle 40s to middle
50s over the plains and the 30s to 40s over the mountains. Winds
will begin to pick up out of the Front Range high country
overnight as a surface trough deepens along the eastern state
border. This will moderate minimum temperatures that night.
Sunday and Monday...an upper ridge...good warm advection and
leeside surface troughing will allow temperatures to climb 10 to
15 degrees above normal both during the day and at night. Maximum
temperatures readings into the 70s will be possible over the
The next system is expected to affect the area late Monday through
Wednesday day. Model timing differences still exist...but are
improving. The European model (ecmwf) has slowed its outlying fast progression
during the latest model cycle and matches better with the Gem. The
GFS remains the slower solution...however has good agreement run
to run with itself. Will increase probability of precipitation for the mountains to likely
and the plains to chance. This storm system looks similar to
today's system...but with cooler temperatures. As the system gets
closer in time and space...will assess the need for any
highlights. Wednesday night into the rest of the work week looks
like another ridge will bring back warmer and drier weather.
Aviation...ceilings will continue to lower this morning with rain
showers developing during the middle morning hours. Colder air will
slowly filter in as atmosphere continues to cool and saturates.
Expect a mix of rain and snow this afternoon and with potential
heavier showers...could change to all snow or for a brief time
this afternoon. Should see all snow after 00z tonight. Snowfall
expected by later tonight to be in the 2 to 5 inch range...highest
at bjc/apa and lower amounts near kden. With warm surface
temperatures any lighter snow will likely just melt. However
heavier snow showers could drop a quick inch of slushy snow on
runways. Surface winds will gradually shift more north and
northeast this morning and remain there for the rest of the day.
Still quite a bit of uncertainty on exact timing of precipitation types
and changeover to snowfall.
Winter Weather Advisory from noon today to 5 am MST Saturday for
Winter Weather Advisory from 3 PM this afternoon to 2 am MST
Saturday for coz039-040.
Winter Storm Warning from 8 am this morning to 2 am MST Saturday
Winter Storm Warning from 6 am this morning to 5 am MST Saturday
Winter Weather Advisory until midnight MST tonight for coz031.