Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 271053

Area Forecast Discussion
National Weather Service Denver/Boulder CO
353 AM MST Sun Nov 27 2016

.SHORT TERM...(Today and tonight)
Issued at 244 AM MST Sun Nov 27 2016

An increasing southwesterly flow aloft will continue over the cwa
this morning, ahead of a 150 kt jet max near the Four Corners
Region. This feature will translate eastward across Colorado and
kick an upper level trough across northern Colorado by 18z today.
There will be a brief period of moderate mid and upper level QG
ascent passing across the cwa through midday. By this afternoon,
increasing subsidence developing with the flow aloft transitioning
to west/northwesterly. In the mountains, snow will increase in
coverage this morning and continue through the afternoon. Across
the northeast plains there will be enough moisture, lift and
instability around with the passage of the trough to warrant at
a slight chance of showers mainly in the morning. By late this
afternoon and evening, spatial cross-sections indicate a fairly
strong mountain wave developing between 00z-06z this evening. The
shear profile is strongest around 03z with a cross-mtn component
of 65 kt around 700 mb. Have opted to issued a High Wind Watch
for the Front Range Foothills this evening with some gusts to 75
mph possible. Across the Urban Corridor and Northeast Plains,
gusty westerly winds late this afternoon and evening in the 40-50
mph range. The stronger gusts should start to taper off after 03z.
Late this afternoon and evening, weakening QG ascent in the high
country will be replaced by better cold air advection and an
improved orographic component as the ridgetop winds will be
west/northwesterly. No changes at this time regarding the Winter
Storm Warnings and Advisories.

.LONG TERM...(Monday through Saturday)
Issued at 244 AM MST Sun Nov 27 2016

Northwest flow aloft will prevail over the Central Rockies Monday
and Tuesday. At ridge top level, westerly winds will be 25 to 40
knots Monday morning. This combined with lapse rates of 6-8 C/KM is
expected to produce orographic snow over the mountains. A short
wave trough embedded in the flow aloft may enhance snow late
Monday and Monday night. Ridge top flow turns northwesterly behind
the trough. In addition to this, cold air advection will help
steepen lapse rates a little more. Plan on keep the winter weather
hi-lites as is. North-northwest flow will weaken, but there
should be enough moisture to keep snow showers going Tuesday.

For the Front Range and eastern plains, windy conditions are
expected Monday and Tuesday. The westerly downslope component is
expected to keep it dry Monday. It will turn cooler Tuesday
behind the trough. Flow turns more northerly and could see a few
light snow showers on the plains Tuesday.

It starts to dry out Tuesday night and Wednesday with a weak
ridge progged to be over the state Thursday. Other than a few
mountain snow showers Tuesday night, and then late Thursday dry
conditions are expected.

For Friday and Saturday, models show an upper level trough diving
south across the western CONUS. The GFS is farther east than the
other models and shows a period of snow across the area. Other
models have this trough too far west to affect the area. For now,
will go with low pops for the mountains and keep the lower
elevations dry. With the lack of any strong warm air advection,
expect temperatures to remain below normal.


.AVIATION...(For the 12Z TAFS through 12Z Monday morning)
Issued at 244 AM MST Sun Nov 27 2016

Light winds this morning as a weak circulation evident over
southeastern Weld County. Will stick with primarily west/northwest
winds at KDEN and KBJC with south/southwest winds at KAPA.
Stronger winds will develop this afternoon following the passage
of the upper trough axis and intensification of the surface
pressure gradient this aftn and evening. Strong westerly winds at
KDEN and KAPA in the 21-03z windows with gusts 40-45kt, even
stronger gusts to 55 kts possible at KBJC. VFR expected through
the period, but could see bkn cigs dropping down 060-080 agl
through 18z with a brief rain/snow shower.


High Wind Watch this evening for COZ035-036.

Winter Weather Advisory from 6 AM this morning to 5 AM MST
Tuesday for COZ033-034.

Winter Storm Warning from 6 AM this morning to 5 AM MST Tuesday
for COZ031.



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