Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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000
FXUS65 KBOU 100351
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
851 PM MST Mon Jan 9 2017

.UPDATE...
Issued at 850 PM MST Mon Jan 9 2017

Radar shows convective development along and ahead of cold front
now just reaching our northern mountains. Lightning data even
shows a few lightning strikes over northwest Colorado.  Snow
intensity has picked up in the convective bands with 1-2 inch per
hour on some of the snowstakes...and this heavier convective snow
will become more widespread through midnight as the front moves
through...already blossoming on the Grand Junction Radar. Airmass
is quite unstable on the 00Z Grand Junction and Salt Lake City
soundings, so convective development no surprise. Very high
precipitable water with nearly 0.50 inch and latest Integrated PW
from GPS-MET shows values near 0.60 inch in NW Colorado now. This
all spells a very efficient snow producer for the mountains so
have bumped up amounts a couple more inches for tonight...and
expectation for an average of 1" per hour rates in the favored
mountain locals. Should see a marked decrease early Tuesday
morning as drier air arrives, but still some accumulation. At this
time, expect sufficient improvement for warning to expire on time
at 11 AM. Until then, driving conditions will be difficult if not
impossible overnight into very early Tuesday across the northern
Colorado mountains.

On the plains, a few showers already developing in the northeast
corner of the state. Along the Front Range, should see a few
showers drift off with the approach and passage of the mid level
front. Will push the low chance of showers a bit further east as
airmass is quite unstable.

&&

.SHORT TERM...(This evening through Tuesday)
Issued at 345 PM MST Mon Jan 9 2017

First order of business...the threat of high winds in and near the
Front Range has diminished considerably in the last hour or two.
The cross mtn pres gradient continues to weaken and the lee slope
mtn wave is showing signs of breaking down. Wind gusts overall in
the foothills have fallen below 50 mph and below 30 mph on the
nearby plains...although still seeing gusts to around 50 mph over
elevated terrain on southwest Elbert and southeast Douglas
counties. Small scale models show wind speeds decreasing in this
area over the next couple of hours.

Next order of business...attention shifts west to the increasing
lift and instability due to cooling aloft associated with a
shortwave trough now passing over Utah and western Colorado.
Strong southwest flow aloft in advance of this wave is forecast to
shift to a west-northwest component overnight and with the shift
cooling at all levels. The shift in winds should enhance
orographic snowfall in the northern mtn ranges starting this
evening where 1-2 inch per hour snowfall rates are anticipated.
Snow levels between 8000 and 9000 ft at the present time will
lower to the valley floors after dark. That`s when the light rain
in the Kremmling area should chance to snow. Axis of max forcing
aligned across northern Utah where radar is detecting a line of
intense convection along sfc cold front. It is this feature with
the cooling and forcing aloft that should help to enhance high
country snowfall this evening. Winds not expected to be as strong
in the mtns tonight...but gusts in the 35-50kt range a good bet...
especially around passage of the cold front. Meanwhile on the
plains could see a few showers move off the foothills overnight.
Temperatures should remain warm enough for most of the night to
keep precipitation as rain. Should rain chance to snow...any
accumulation should be minimal at best.

For Tuesday...should see snowfall in the high country winding
down through the morning as drier and more stable air moves in on
the back side of the upper trough. Should still see areas of snow
showers but additional accumulations will be on the low side. On
the plains...another dry day but slightly cooler and more clouds
with passing trough. Winds also much lighter...esply along the
foothills.

.LONG TERM...(Tuesday night through Monday)
Issued at 345 PM MST Mon Jan 9 2017

Wintry weather looks to continue in the mountains for much of this
week under a continued...moist westerly flow over Colorado. The
next bump of moisture will be late Tuesday night and Wednesday for
the mountains as next upper level jet plows into Southwest
Colorado. Could need further hilites for snow in the mountains but
will not issue one for now due to current warning ongoing in the
mountains.

Cold front will back into the plains of northeast Colorado on
Wednesday afternoon with colder airmass behind it. Have lowered
temperatures for the far plains during the afternoon. Another
front moves in later Thursday and Friday with colder temperatures
for all the plains with even a slight chance for snow on the
plains.

Finally some drying and warming for the weekend as the upper trof
moves south and east of Colorado.

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 850 PM MST Mon Jan 9 2017

VFR conditions next 24 hours. Should see isolated to scattered
rain showers move off the Front Range through midnight, then
temperatures aloft get cold enough for a low threat of snow
showers before significant drying and subsidence moves across the
Front Range. Winds quite variable between northwest and southwest
and could be gusty to 25+ knot gusts possible due to showers in
vicinity and downslope. Similar winds expected Tuesday, although a
few gusts could push 30 knots if sufficient mixing occurs.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Winter Storm Warning until 11 AM MST Tuesday for COZ031-033-034.

&&

$$

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



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