Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Denver/Boulder Colorado
1147 am MDT Monday Mar 10 2014
Short term...current forecast looking pretty good. Substantial
wave cloud just east of the Front Range with plenty of sunshine
elsewhere. Temperatures will be about the same as yesterday...
except 5 to 10 degrees cooler under the wave cloud. All this
already anticipated. NAM continues to back away from the snow for
tomorrow...but GFS less so...it still looks a lot like our
forecast and does not weaken the trough until it is past Denver.
Will consider further but still looks like the idea of a quick
shot of snow and strong winds coming through Denver Tuesday
afternoon seems reasonable. Amounts will be limited by the short
duration...maybe only 2-4 hours...and there should be great
improvement by early evening.
Aviation...VFR through tonight. Winds going northwest at kden/kapa at
this time...should stay that way through the day. Tendency back
toward SW this evening but then northwest again ahead of the front later
Previous discussion... /issued 349 am MDT Monday Mar 10 2014/
Short term...one more warm and dry day is in store with similar
temperatures as yesterday. Additional moisture will move into
flow aloft becoming more west-southwest and will produce more
wave clouds today. This in combination with weak cold advection
from the northwest should produce temperatures a few degrees
cooler in areas over the mountains...foothills and the northern
and Western Plains. Still expect readings near 70 over the plains
and in the 30s over the highest peaks to 40s and low 50s over the
High Mountain valleys. Surface leeside troughing will keep gusty
west winds in the eastern Front Range mountains and foothills.
The next system will begin to move into the state tonight from the
northwest. With good qg vertical motion and westerly mountain top
flow...will start to see some light snow late this evening over the
northern mountains...then the cold front begins to sink south over
northwestern Colorado for snow to ramp up over the
park...Gore...Medicine Bow and Laramie ranges after midnight.
Orographics and synoptic components may allow for snowfall rates of
a half to one inch per hour rates especially over the park and Gore
ranges. The surface low over the plains will begin to sink south
over the plains with winds turning northwest ahead of the main front
expected Tuesday morning. Gusty west prefrontal winds will likely
keep minimum temperatures moderated overnight.
Long term...at this point confidence with regard to tuesdays
weather is actually lower than 24 hours ago. While the same
general weather pattern remains in tact with the upper trough and
strong cold front moving across the area...details on resultant
weather are in question. The latest models have reversed trends on
yesterdays faster arrival and have now actually slowed the system.
Not totally sure to buy off on this at this point so only raised
early morning high temperatures a few degrees...due mainly to warmth
overnight tonight. Once front moves in...temperatures will fall
through the day with strong cold advection.
With regard to precipitation...models seem to wring most moisture
and precipitation out over Montana and Wyoming. However...there is
still good and deep lift to our north which does push south/
southeast across Colorado. The strongest q-g signal is in the
boundary layer due to upslope...with weaker lift aloft and mainly
early in the day. There is a 3-6 hour period of upslope flow and
steep lapse rates as well with potential instability indicated on
forecast soundings...so we could get convective snowfall. Almost
all model quantitative precipitation forecast however is less than impressive and not sure why
based on the parameters mentioned above. Will still maintain the
snowy forecast for Tuesday at this point given the favorable
parameters. Temperatures will be falling behind the front and
strong gusty winds with peak gusts between 40 and 50 miles per hour on the
plains could also lead to blowing and drifting snow in areas that
see accumulating snowfall. Hard to narrow down accumulations at
this point but most areas should stay shy of advisory criteria
snowfall. Wildcards however would be threat of convection...
blowing snow....and amount of cooling which could lead to snow
covered roads despite the recent warmth.
Mainly dry weather is then expected through the rest of the work
week although latest model trends were to bring the secondary low
development in the Desert Southwest east across the southern
rockies by Thursday/Friday. Most precipitation would still stay well to
our south so only low probability of precipitation for park/Summit County area.
Temperatures will moderate to or slightly above normal levels
Wednesday through Friday.
Next chance of precipitation will be Saturday when another fast
moving upper level disturbance and cold front are prognosticated to reach
Aviation...VFR conditions expected through 12z Tuesday. High
clouds will continue to stream across Colorado today. South-
southwest winds expected through most of the day. At
kbjc...a more westerly wind will prevail with a few gusts to 20
knots possible this morning...then again tonight. A cold front is
expected to move in from the north Tuesday morning with strong
northerly winds. Ceilings not expected to lower until after 18z
Tuesday with snow developing shortly after.