Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

FXUS65 KPUB 111736

Area Forecast Discussion
National Weather Service Pueblo CO
1036 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 CO. 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 18Z TAFS through 18Z Thursday afternoon)
Issued at 1034 AM MST Wed Dec 11 2019

VFR at all taf sites the next 24 hrs with high level cirrus
overcast at times. Winds will continue to follow typical diurnal




National Weather Service Glossary of Abbreviations