Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Pueblo Colorado
417 am MST sun Dec 8 2013
Short term...(today and tonight)
issued at 352 am MST sun Dec 8 2013
Currently...a fast moving upper level trough is currently moving
into The Four Corners region spreading snow across The Rockies.
Current observation and web cams indicate the San Juans are seeing heavy
snow...and areas around Monarch are seeing decent snow rates.
Elsewhere...radar indicates areas of light snow across the San Luis
valley and eastern mountains...which has spread east into the I-25
corridor. Temperatures are cold with most areas in the single
Today...the upper level trough will continue to track east across
southern Colorado through this afternoon. Current thinking is that
the best lift across the Continental Divide will occur this morning
producing periods of moderate to heavy snow...especially over the
San Juan range...and to a lesser extent over the central mountains.
The high-res models have very limited snowfall for the eastern
mountains and the plains this morning. Have a feeling the southern
sangre Delaware cristo range will see periods of localized moderate snow
this morning. On the plains...snow will likely remain confined to
along and west of the Interstate.
The high-res models differ slightly on when they want to cut off
snow across the Continental Divide with the majority having the
heaviest snow ending by 15z as the upper system begins to eject
eastward. Followed this timing...with decreasing snow intensity by
middle morning with light snow lingering through the afternoon. Some of
the high-res model solutions are hinting that the snow may come to
an end altogether for the San Juan range after 18z when the upper
level flow turns northwesterly effectively cutting off orographic
lift but have kept light snow in the forecast through the
afternoon. The northwest flow should keep light snow going over the
central mountains into this evening. As for additional snowfall
totals...the San Juans will likely see an additional 4 to 8 inches
with locally higher amounts while the central mountains see an
additional 2 to 5 inches. The eastern mountains...especially the
southern sangres could see a couple of inches...while just a dusting
is expected across the lower elevations west of I-25.
Afternoon highs will remain cold across the region with generally
teens to lower 20s for the lower elevations.
Tonight...the upper system will move into the Central Plains while a
secondary shortwave digs south into Utah. Upper level flow will
remain out of the northwest which should keep periods of light snow
going for the central mountains. An additional inch or two is
possible along the northwest facing slopes. Cold air will settle
southward across the plains behind a cold front. Expect overnight
lows to fall below zero for much of the region heading into Monday
Long term...(monday through saturday)
issued at 352 am MST sun Dec 8 2013
Secondary upper trough will move across Colorado on Monday...though there's
not a lot of moisture with this system. Nam12...GFS...and European model (ecmwf)
spread some precipitation along the southern/eastern border on Monday
in area of upglide ahead of the upper trough. Some light snow may clip
through southern/southeast portions of Las Animas and Baca
counties...however the remainder of the plains will stay dry.
Meanwhile...central mts will continue to see some orographic snow
showers...but models seem to be drier and drier every run.
Temperatures on Monday will drop back a few degrees behind the cold
front...but won't be as frigid across the lower elevations as the
past few days.
Skies clear out Monday night...however Lee troffing across the southeast
plains should keep a ribbon of warmer lows (single digits to around
10 degrees along the lower eastern slopes of the southeast mts. Given the
dry airmass...areas that decouple could be quite cold...with
guidance giving -20 at kals. This looks reasonable and suspect
other valley locations across the high country could see similar
readings. For the far eastern plains...it will all depend on where
the winds can keep the atmos mixed. Have played locations along and
west of I-25 slightly warmer (5-10 degrees) with around 0 to
negative single digits in the normal cold spots across the southeast
Northwest flow aloft will persist over the area through Wednesday.
Tuesday should see a warm up across the lower eastern slopes of the
southeast mts/I-25 corridor as westerly winds spread down into the surface Lee
trough. Farther east...suspect the cold air will modify some but
won't mix out entirely...so have gone slightly colder across the eastern
plains. Where winds mix down...could even see some Lower-Middle 40 degree
readings along the I-25 corridor...but hesitate to go that warm as
some of these areas may have some residual snowpack to deal with
after this mornings system clears the area. Another front drops
southward through the region Tuesday night behind the next shortwave
moving through the flow. Central mts may pick up some light
snow...and temperatures on the plains will loose some ground for Wednesday
behind the front.
Temperatures should make a nice rebound for Thursday and Friday.
There are some differences with how the long range models handle a
closed low which gets picked up off the coast of Baja California and ejects to
the south of Colorado as the next trough drops into the Pacific northwest on
Thursday night/Friday. For now...Thursday looks to be the warmest
day...though light winds across the area may limit mixing for some
of the valley locations with residual snow pack. The plains should
rebound back into the 40s...perhaps near 50 for some locals. GFS
brings another front through the area on Friday which may knock back
highs a bit...but not much. European model (ecmwf) looks a little slower with this
front. Then the next upper trough may begin affecting western areas
Friday night and Saturday...though this is where differences in the
models really come to light as European model (ecmwf) keeps this system back along the
West Coast...while GFS brings it across Colorado. If GFS is correct then
mts areas could see another round of snow with another cold front
for the southeast plains. Ec would suggest dry and mild. Current grids
portray a middle of the Road solution for now. -Kt
Aviation...(for the 12z tafs through 12z Monday morning)
issued at 352 am MST sun Dec 8 2013
Kals...periods of light snow will continue this morning with MVFR to
IFR ceilings and visible. Expect improving conditions after 14-15z this
morning with VFR this afternoon. A few wind gusts out of the west
are possible in the 20-25 knots range this afternoon.
Kcos...periods of light snow and low ceilings will bring IFR to LIFR
conditions to the terminal this morning. Expect improving ceilings and
snow dissipating by 15z with the passage of a cold front which will
bring a northerly wind shift. Expect VFR by this afternoon and into
Kpub...ceilings will remain low this morning around 1 kft. There have
been occasional snow as well...but confidence in snow hitting the
terminal is low at this time. A cold front will drop south across
the area by 17z bringing a northerly wind shift. We should also see
improving conditions to VFR behind the cold front. Model soundings
indicating the potential for freezing fog after sunset. Mozley
Winter Weather Advisory until 5 PM MST this afternoon for coz066-
Winter Storm Warning until 5 PM MST this afternoon for coz068.
Winter Weather Advisory until 5 am MST Monday for coz058>061.