Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 301103

Area Forecast Discussion
National Weather Service Denver/Boulder CO
403 AM MST Wed Nov 30 2016

.SHORT TERM...(Today and tonight)
Issued at 403 AM MST Wed Nov 30 2016

A large upper level low over the Great Lakes and a weak ridge
moving across the Great Basin will result in a northwest flow
aloft over Colorado. Airmass will be drying, so expected mostly
sunny skies over northeast Colorado. Some moisture will be trapped
over the higher terrain, so expect areas of clouds with light
snow/flurries possible. Any snowfall will be light and less than
an inch. Not much change in the temperature of the airmass. Due to
sunny skies today, expect it to be a couple degrees warmer with
highs in the upper 30s to lower 40s across northeast Colorado.

Flow aloft will turn westerly late tonight ahead of a trough
moving into the Northern Rockies. Moisture will increase over the
mountains and expect to see a slight increase in the light snow
towards 12z Thursday. Again, any accumulation will be light.

.LONG TERM...(Thursday through Tuesday)
Issued at 403 AM MST Wed Nov 30 2016

Thursday looks dry for the plains with a weak shortwave ridge
passing overhead accompanied by a 30-40kt w-nwly flow aloft. Flow
aloft becomes southwesterly during the day as a diving jet maxima
carves out a shortwave trough over Utah. Models show this feature
continuing to propagate south-southwestward away from the CO Front
Range and ending up over the lower Desert Southwest where they show
it spiraling up into a deep closed low. Downstream from this
deepening trough models show moderate jet level flow transporting
relatively warm and moist air up over Colorado potentially
generating precipitation in the form of snow over higher elevations
of the CWA by Thursday afternoon. Southwest flow not all that
favorable for snow production in our mtns...but with increasing lift
and mid-level instability could see anywhere from 2-5 inches of snow
of higher west/southwest facing slopes by Friday morning. QG omega
fields continue to indicate modest large scale ascent over the the
forecast area Friday morning and in the presence of an easterly
/upslope flow on the plains could see a few bands of light snowfall
extending out over the adjacent high plains before the noon hour. In
the high country...orographic snowfall is expected to wind down
through the day as the Desert SW low continues to drop southward.
Do not see more than another inch of snow at best over high
elevations and mainly south of I-70. For the plains...not counting
on any appreciable accumulation but it certainly will be cold enough
with highs not expected to climb much above freezing all day under a
mostly cloudy to overcast sky.

A majority of the models still show the business end of the above
mentioned upper trough tracking east over northern Mexico and
eventually across Texas as an open wave by early next week. However
the GFS model shows this shortwave trough phasing with a much larger
longwave trough forming over the Great Basin and once merged...the
lesser wave lifts northeast over Colorado possibly bringing the
first of many chances for snowfall to the high country on Monday. It
doesn`t look like much snow...perhaps an inch or two at the highest
elevations since temperatures will be a bit warmer. During the
afternoon could see a few light rain showers drift out over the I-25

Looking ahead to the period Monday night through Wednesday...some of
the coldest air of the season is projected to spill south out of
western Canada as an extensive longwave trough forms over the
western CONUS during the first half of next week. Models show
this trough and cold airmass slowly migrating eastward across the
Rocky Mtn region bringing well below average temperatures...plenty
of cloud cover and a number of opportunities for snow--both mtns
and plains. Still too early to predict snow amounts. However
temperatures by Tuesday may not climb out of the 20s...and that
may go for readings on Wednesday depending on the extent of snow
coverage at that time. This pattern does not look like a big snow
producer...more cold than anything. By Thursday models indicate
return to warmer and drier conditions with a large upper ridge
building to our west.


.AVIATION...(For the 12Z TAFS through 12Z Thursday morning)
Issued at 403 AM MST Wed Nov 30 2016

VFR conditions are expected through 12z Thursday under mostly
clear skies. Southerly drainage winds at KDEN and KAPA will become
light after 12z. After 18z, winds are expected to turn northeast
to easterly. After 00z, winds will return to a normal southerly
drainage direction.




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