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fxus65 kbou 200413 
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Area forecast discussion
National Weather Service Denver/Boulder Colorado
913 PM MST Tue Nov 19 2019

Update...
issued at 910 PM MST Tue Nov 19 2019

A wave of moderate to heavy showers is moving across western
Colorado this evening with sunlight mountain reporting heavy snow
within the last hour. High resolution models are a bit too slow
and weak with this area of precipitation. Consequently, with the
leading edge of the precipitation nearing Eagle, I increased pops
tonight over the mountains of grand and Jackson counties. There's
a lot of terrain these showers will have to make it through so
still thinking quantitative precipitation forecast amounts will be light tonight.

The 00z NAM models increased snow totals through Thursday morning
while the 00z GFS decreased snow totals so no changes were made
to the forecast snow totals. With the relatively warm origins of
this storm, I still tend to agree with holding off on a Winter
Weather Advisory for now.

&&

Short term...(this evening through wednesday)
issued at 338 PM MST Tue Nov 19 2019

High clouds will continue to stream over Colorado tonight,
thickening after midnight as a weak shortwave ahead of the main
trough approaches. There will be a gradual increase in moisture
over the mountains, and some very light snow may begin along The
Divide late tonight. More likely this will spread across the
mountains Wednesday morning. For the plains, it will be cloudy
with the cold front moving through in the morning. This will bring
increasing low level moisture and upslope convergence along the
foothills. There may be some very light rain or snow in the middle
of the day from the initial convergence over the front, but the
better forcing arrives late in the day and we expect more
widespread rain/snow to be spreading east across the plains in the
late afternoon. This is still expected to be light. By early
evening, it should be cold enough for all snow, but if the
precipitation starts earlier there will be some rain to begin
with. Between the fairly warm air, warm roads, and generally light
precipitation rate, there shouldn't be much impact on the
afternoon rush hour in Denver, and limited impact if any in the
foothills.

Long term...(wednesday night through tuesday)
issued at 338 PM MST Tue Nov 19 2019

An area of predominantly snow will be tracking northeast across
Colorado Wednesday evening. Precipitation may briefly begin as
rain before getting cold enough for snow. This area of
precipitation will be associated with the initial short wave
trough ejecting northeast across the central rockies. By mid to
late evening this trough should exit Colorado. Subsidence behind
the exiting short wave trough will bring a drier period late
Wednesday night and Thursday. Weak upslope flow and moist low
levels may keep light snow or freezing drizzle going along the
foothills through Wednesday night and into Thursday morning.

The main upper level low centered near Las Vegas Wednesday night
will slowly shift eastward and fizzle out by Thursday night. A new
closed low is expected to form Thursday night over eastern
Colorado and linger into early Friday. Models still disagree on
where this new low forms, so confidence in forecast is lower than
usual. Expect to see another round of snow late Thursday into
early Friday as lift forms over the area. Location of the best
snow is still uncertain. Models not too excited with this system
with quantitative precipitation forecast amounts less than third inch. Thursday will be the
coldest day of the week with temperatures struggling to climb
above freezing. Will start to see a warm up Friday as some
clearing takes place.

No winter weather advisories or winter storm watches/warnings at
this time. A few mountain roads may become slick Wednesday evening
before the snow ends. For the lower elevations, a warm start to
the day and temperatures staying near freezing should keep most of
the roadways wet. Though can't rule out some slick spots under
the heavier snow. For Thursday night and Friday, expect another
round of light snow and will not issue anything for this second
event.

A dry northerly flow aloft will prevail Saturday behind the
exiting closed low. Flow aloft backs to the northwest for Sunday
as a trough moves onto the Pacific northwest coast. Temperature
will be mild this weekend with highs in the 50s Saturday over the
Front Range and eastern plains. Expect a slight warm up on Sunday
with some 60s possible across the lower elevations.

For early next week, models show an upper level trough diving
southeast across the central rockies sometime late Monday into
Tuesday. A cold front will accompany this system and reinforce the
colder air. The details still need to be worked out, but cool
temperatures with a chance for snow for Monday night and Tuesday
looks like a good start. Could be some brief rain on the front end
of this system on Monday.

&&

Aviation...(for the 06z tafs through 06z Wednesday night)
issued at 910 PM MST Tue Nov 19 2019

VFR tonight. A cold front will move through the Denver area around
17z Wednesday, with north winds gusting between 20 and 30 knots
and lowering ceilings behind it. Precipitation will begin around
22z with ceilings and visibilities decreasing through the late
afternoon and evening. The heaviest band of precipitation will
move through den between 02z and 06z with LIFR conditions
possible.

&&

Bou watches/warnings/advisories...
none.
&&

$$

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