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Area forecast discussion
National Weather Service Pueblo Colorado
412 am MST Wed Dec 11 2019

Short term...(today and tonight)
issued at 406 am MST Wed Dec 11 2019

Currently...GOES satellite imagery and upper-air analysis are
indicating a ridge of high pressure beginning to move into the Rocky
Mountain region, which is producing some high clouds across southern
Colorado. These high clouds have slightly hindered this morning's
radiational cooling for the time being. Temperatures are generally
in the teens and low 20s across the area with some lower temps in
the typical cold pockets. However, winds along the eastern slopes
have stayed breezy, keeping temperatures there in the 30s. To our
west a trough of low pressure can be seen digging into the Great
Basin this morning.

Today and tonight...the ridge of high pressure is expected to
propagate through Colorado today. In addition, a deepening Lee
trough is anticipated to move into the eastern plains today, which
will bring some breezy conditions this afternoon and evening.
Temperatures will also be warmer today across the plains with
highs reaching the 50s, while the high valleys should see highs in
the upper 30s to mid 40s. The trough of low pressure currently
over the Great Basin is expected to quickly move through the
region tonight, mainly bringing cloud cover to southern Colorado,
which will help to keep temperatures slightly warmer tonight than
they have been the past couple of nights. Lows tonight are
expected to be in the 20s across the plains and single digits and
teens in the high valleys. Outside of the added cloud cover, this
disturbance brings a very slight chance of snow showers to the the
central mountains tonight.

Long term...(thursday through tuesday)
issued at 406 am MST Wed Dec 11 2019

..prolonged snow event for the mountains Thursday night through
Sunday with snow spreading into the adjacent plains late weekend...

Upper jet translates through the western U.S. On Thursday sending
increasing moisture into the central mountains where snow showers
will develop during the afternoon. Some light accumulations will be
possible across the higher peaks north of Cottonwood Pass during
the afternoon. The remainder of the area will remain dry and mild
with temperatures topping out in the 50s across the
plains...upper 30s and 40s for the valleys...and mainly 20s and
mid 30s across the mountains. Winds will be increasing especially
across the mountains during the afternoon with the approach of the
upper jet.

A prolonged period of snow sets up across the central mountains as
favorable northwesterly orographic flow persists beneath strong
upper jet. There will be periodic waves of forcing as impulses
swing through the flow. Looks like more of a steady light to
moderate snow event for the eastern sawatch and western mosquito
ranges, though snow amounts easily stack up over a foot through
Saturday, particularly north of Cottonwood Pass (with additional
snowfall expected through sunday). Given the long duration event,
it isn't hard to achieve warning criteria amounts (12+ inches) up
that way, with advisory level snow amounts possible for the
central part of Lake County. Combined with strong winds across the
higher elevations and passes, suspect winter storm highlights
will eventually be needed given the potential adverse impacts to
travel exacerbated by blowing snow. Event is just getting started
in the 4th period with the heavier snow holding off until later,
so will let day shift get a better look at timing before hoisting
highlights. Looks like heavier snow hits in Friday night into
Saturday as next impulse moves across and cold air advection helps
to steepen lapse rates aloft.

As several rounds of moisture move through, snow showers will spread
into the higher peaks and west facing slopes of the southeast
mountains at times, but overall accumulations remain light.
Temperatures remain mild across the plains through Friday.

The upper jet sags southward Saturday night/Sunday night as the
next upper trof translates eastward across Colorado. Showers will spread
southward into all of the mountains, and into the adjacent plains
as a cold front drops southward and upglide sets up overtop the
mid level baroclinic zone. Temperatures appear to be trending
colder for this period across the plains, and suspect that Sunday
will see a widespread light snow for much of the southeast
mts/plains as the upper trough approaches. There could be the
potential for some moderate accumulations on Sunday for the
southeast mountains as cold air deepens and the potential for a
period of northeast upslope flow develops. System is fairly
progressive though, so appears advisories at best may be needed
for the southeast mtns. That said, there are still some timing
differences between the long range models, with ec and Canadian a
tad faster than GFS. If system becomes less amplified then snow
amounts could be less as well. Have trended temperatures down for
Sunday given good agreement that colder air will work in and this
will be a mainly snow event for the plains.

Drier weather spreads in for Monday across most of the area...though
orographic snow showers may persist across the central mountains
under northwest flow. Upper ridging returns for Wednesday with dry
and warmer conditions for all areas. -Kt


Aviation...(for the 12z tafs through 12z Thursday morning)
issued at 406 am MST Wed Dec 11 2019

VFR conditions are expected at all three taf sites (kals, kcos, and
kpub) for the next 24 hours with generally diurnal winds.


Pub watches/warnings/advisories...


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