Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50

704
FXUS65 KBOU 050915
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
215 AM MST Mon Dec 5 2016

.UPDATE...
Issued at 213 AM MST Mon Dec 5 2016

Have just issued a high wind warning for the Front Range foothills
from now through 19z this morning. winds overnight have been in
the 30-50 mph range but are expected to increase even more between
15-18z with stronger subsidence and higher stability. Cross
sections show cross barrier flow increasing to 50-65kt by 12z.

UPDATE Issued at 841 PM MST Sun Dec 4 2016

Have updated the grids for tonight, slowing down the onset of
any snow in the mountains until after midnight, primarily
impacting zone 31 based on the last few HRRR runs. Also made some
wind adjustments in the the foothills. Still expected strong winds
overnight and Monday morning, but no highlights with gusts
primarily in the 50-65 mph range.

&&

.SHORT TERM...(This evening through Monday)
Issued at 328 PM MST Sun Dec 4 2016

Westerly flow aloft will be increasing over northern Colorado
tonight as an upper level jet moves in from the Pacific Northwest.
Moisture associated with the developing flow pattern will also be
on the increase over the mountains by 06z and continuing through
Monday. The core of the upper level jet will be staying over
Wyoming with ridgetop flow in Colorado peaking out at around 70
knots. Model cross sections indicate that the fastest flow will
remain over the ridges, without much of a lee-slope mountain wave
developing. Quasi-geostrophic diagnostics also show a lack of
strong subsident forcing overnight, which may be why a strong wave
does not develop. At any rate, the strongest winds are expected to
remain above 10,000 to 11,000 feet, with lesser impacts down in
valleys and population centers. No highlights will be issued.
Light snow will also be developing in the mountains overnight, but
only light amounts, up to about 4 inches, are expected through
tomorrow afternoon.

On the plains, one last mild day will be in store, but by mid-
afternoon cooler air is expected to begin moving in from the
north. High temperatures in the mid 40s to lower 50s will beLIGHTWEIGHT AND HIGH PROFILE VEHICLES SHOULD USE
  CAUTION ESPECIALLY ALONG NORTH TO SOUTH ORIENTED ROADWAYS
  INCLUDING THE PEAK TO PEAK HIGHWAY, FROM BLACKHAWK TO ESTES
  PARK, AND HIGHWAY 287 NORTH OF FORT COLLINS TO THE WYOMING
 STATELINE. BE PREPARED FOR STRONG AND SUDDEN CROSSWINDS.
possible, primarily by the lunch hour. Dry conditions will prevail
through later Monday night. Afternoon gusts on the plains will be
in the 25 to 35 mph range.

.LONG TERM...(Monday night through Sunday)
Issued at 328 PM MST Sun Dec 4 2016
LIGHTWEIGHT AND HIGH PROFILE VEHICLES SHOULD USE
  CAUTION ESPECIALLY ALONG NORTH TO SOUTH ORIENTED ROADWAYS
  INCLUDING THE PEAK TO PEAK HIGHWAY, FROM BLACKHAWK TO ESTES
  PARK, AND HIGHWAY 287 NORTH OF FORT COLLINS TO THE WYOMING
  STATELINE. BE PREPARED FOR STRONG AND SUDDEN CROSSWINDS.
A dramatic change in the wx ptrn will occur Tue into Wed as an upper
level trough moves along with a couple of cdfnts.  Mtns will see
some snow Mon night into early Tue however best chc of heavier snow
will be Tue aftn and night when best QG ascent moves across in
association with deeper moisture.

Across nern CO first shot of colder air will move in Mon night into
early Tues with a brief shot of upslope flow Mon night.  Overall LIGHTWEIGHT AND HIGH PROFILE VEHICLES SHOULD USE
  CAUTION ESPECIALLY ALONG NORTH TO SOUTH ORIENTED ROADWAYS
  INCLUDING THE PEAK TO PEAK HIGHWAY, FROM BLACKHAWK TO ESTES
  PARK, AND HIGHWAY 287 NORTH OF FORT COLLINS TO THE WYOMING
 STATELINE. BE PREPARED FOR STRONG AND SUDDEN CROSSWINDS. with
lack of QG ascent Mon night thru Tue morning and a dry lyr in the
lower levels will only see a chc of light snow mainly in and nr
the foothills. Highs on Tue will be in the mid 20s to around 30
across the plains.

By late aftn into Tues night upslope flow will gradually increase as
a sfc low forms over srn CO and a secondary shot of colder air moves
into nern CO.  Meanwhile QG ascent will increase across the area
which will lead to a gradually increase in snow in and nr the
foothills and across the rest of the plains Tue night.  Based on
current data and timing of upper level trough snow may linger into
Wed morning as well before gradually ending in the aftn.  As for
amounts HI RES WRF and SREF Plume data indicate advisory amounts fm
the foothills across the plains with the potential for heavier
amounts around the Denver area.  Confidence is not high enough to
issue a watch at this point since the heaviest snow at lower
elevations will be from Tues night into Wed morning.  Meanwhile
highs on Wed will only be in the teens across the plains.

For Wed night into Thu drier air will spread across the area in nw
flow aloft.  Outside of a chc of light snow in the mtns Wed night it
will be dry thru Thursday.  Morning lows on Thu will likely be below
zero across much of the area.  As for highs on Thu readings will
only be in the upper teens to lower 20s across the nern Co.

For Fri and Sat the flow aloft will become more wly with moisture
affecting the mtns both days with a good chc of orographic snow.
Across nern CO it will be dry with moderating temps on Fri as
downslope flow develops with readings mainly in the 30s.  On Sat a
wk fnt may move across nern CO which would keep readings in the 30s.

On Sun a weak upper level trough is fcst to move across bringing
another chc of snow to the mtns.  Across nern CO will not mention
any pcpn and will keep highs in the 30s.

&&

.AVIATION...(For the 06Z TAFS through 06Z Monday night)
Issued at 841 PM MST Sun Dec 4 2016

VFR conditions through 06z Monday night but could see the
potential of some ils restrictions with bkn cigs 050-060 kft agl
developing after 00Z. Winds will be out of the west or southwest,
especially over the western portions of the Denver area where
gusty winds are expected at times overnight, primarily impacting
KBJC. Winds are expected to increase Monday afternoon and evening
as an initial surge of cold air begins moving into northeast
Colorado. Northwest to northerly in the afternoon, then north to
northeasterly Monday evening.


&&

.BOU WATCHES/WARNINGS/ADVISORIES...
High Wind Warning until noon MST today for COZ035-036.

&&

$$

UPDATE...Entrekin
SHORT TERM...Dankers
LONG TERM...RPK
AVIATION...Cooper



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.