Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

Home | Current Version | Previous Version | Graphics & Text | Print | Product List | Glossary On
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
000
FXUS65 KBOU 161828
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1128 AM MST Thu Nov 16 2017

.UPDATE...
Issued at 1014 AM MST Thu Nov 16 2017

Satellite pictures are showing increasing upper level moisture to
our immediate west. Lee wave cloudiness in increasing over the
plains right now. Fairly brisk southwesterly low level winds are
covering much of the CWA right now. Temperatures have warmed into
the lower 70s over some of the plains right now. Will make a
couple cosmetic changes to sky cover and winds.

&&

.SHORT TERM...(Today and tonight)
Issued at 333 AM MST Thu Nov 16 2017

The day will start out dry and mild beneath a passing upper level
ridge, with lowest humidity values along the east face of the
Front Range--the product of downslope flow. Sunshine and a warm
southwest flow aloft should have little problem pushing afternoon
temperatures up into the low/mid 70s on the plains, with warmest
readings in areas exposed to gusty west-southwest winds such as
along the base of the southern foothills and over the Palmer
Divide. Dry fuels, unseasonably warm temps, gusts to around 20 mph
and min RHs down around 15 pct will create high fire danger
conditions for a few hours this afternoon specifically in eastern
Douglas, Elbert and Lincoln counties where we could see pockets of
active rangeland fire behavior, but not enough activity or
intensity to warrant a red flag warning. In the high country,
specially north of I-70, mid and high clouds will be on the increase
through the day as a powerful (150-160kt) Pacific jet stream
transports a plume of moisture rich maritime air towards Colorado.

Models show this jet and its accompanying moisture slipping south
over the northern mtns and high valleys overnight, with scattered
to numerous rain/snow showers developing over higher elevations
after midnight. Snow level will start out high up around 10,000
feet msl in the evening, then lower to around 9000 feet msl by
morning. A strengthening west-southwest flow overnight will favor
the Park and Gore Ranges where upwards of 4 inches of wet snow
could pile up on windward slopes and high passes by morning. Snow
amounts in mtn areas south of there much less than that. From the
Front Range eastward, conditions should remain dry and relatively
mild overnight with a continuation of downslope flow.

.LONG TERM...(Friday through Wednesday)
Issued at 333 AM MST Thu Nov 16 2017

Main concern centers around powerful storm to impact Colorado
mountains Friday and Friday evening and the potential for heavy snow.
Across lower elevations, the main impact from this storm will be
the strong winds expected with the cold front late Friday
afternoon and some potential for light snow showers Friday evening.

On Friday, Moisture depth will continue to increase over the
mountains, but 700mb temperatures will still be warm, generally
around 0C during the am while orographic wind direction remains from
the southwest. Main impact in the mountains will be later Friday
afternoon and evening when the cold front moves through and
increasing orographic flow and steepening lapse rates. Could see
snowfall rates of 1-2 inches per hour with the front and banded
precip with the jet streak. This will certainly create some impact
along the I-70 corridor most likely from around 4 pm through 8
pm.

As for the hilites, will already have a winter storm warning in
place for zone 31 due to more favorable sw orographic flow. For
now will maintain the watch for zones 33 and 34. May not see the
heavier snow develop until Friday afternoon especially zone 34.
Suspect the hilites are running too long into Friday night and
suspect they can be dehoisted by midnight Friday night.

Across lower elevations, the associated strong cold front will
drop southward from late afternoon through early evening. Given
strong pressure rise behind front and subsidence could see gusts
in the 30-45 mph range over the northeast plains. Main change to
forecast was to increase winds over the plains for Friday night.
QG fields showing strong subsidence developing behind the trof.
Will still maintain scattered pops for now as jet dynamics will be
battling the increasing downslope northerly flow. Best chance for
any precip would be down south of Denver over the Palmer Divide
with better favored upslope component.

High pressure ridge aloft builds into the region this weekend with
drying and warming conditions. Temperatures will once again
rebound to above normal readings with 50s/60s through much of next
week. Next chance of snow for the mountains looks to come in
around the middle of next week.

&&

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1014 AM MST Thu Nov 16 2017

Decent south-southwesterly low level winds should continue much of
today through tonight. There will be no ceiling issues through
tonight.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Winter Storm Watch from late tonight through late Friday night
for COZ033-034.

Winter Storm Warning from midnight tonight to 5 AM MST Saturday
for COZ031.

&&

$$

UPDATE...RJK
SHORT TERM...Baker
LONG TERM...Entrekin
AVIATION...RJK


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