Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 150458
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
958 PM MST Sat Jan 14 2017

.UPDATE...
Issued at 942 PM MST Sat Jan 14 2017

Currently the 500 mb low is over the northern Baja and is slowly
tracking eastward. Currently no precipitation is falling across
the CWA...with only some light showers across far southeastern
Colorado. The storm track has not changed much past couple of
runs...with the main difference being a later start of
precipitation in Denver. Therefore...have delayed higher pops
across Metro Denver til around noon.

&&

.SHORT TERM...(This evening through Sunday)
Issued at 322 PM MST Sat Jan 14 2017

Colorado is under southwesterly flow aloft as a cutoff low spins
over the Baja. The first band from the cutoff low over Baja has
pushed north over the forecast area this afternoon bringing up to
a couple inches of snow over the mountain, but little if nothing
over the drier plains. There will be a break this evening and into
the overnight hours before deeper moisture pushes up from the
south. Areas of snow will spread north, but warmer air at the
lower to mid levels will be pushed up with this system as well, so
some freezing drizzle and rain may occur over the eastern plains
as well due to below freezing surface temperatures. Light snow
will spread north through the day, with the mixed precipitation
area expected to mainly stay along and east of a line from Limon
to Akron to Sedgwick, though some isolated areas further west
cannot be ruled out. Models have been trending further east and
south with the main system, so have adjusted PoPs to favor areas
along and south of I76. Have issued a Winter Weather Advisory for
the Palmer Divide and far eastern plains to highlight the
hazardous conditions due to accumulating snow of 3 to 6 inches and
freezing rain. In this kind of pattern, the high country along
and south of I70 and possibly up part of the Front Range will see
some snow, about 1 to 4 inches. Temperatures will hover in the low
to mid 30s across the plains, though areas along the urban
corridor will be in the mid to upper 30s if the system pulls east
enough.

.LONG TERM...(Sunday night through Saturday)
Issued at 322 PM MST Sat Jan 14 2017

The latest 12Z ensembles and ECMWF now show reasonable consensus
in the storm track from southeast New Mexico through the Texas
Panhandle and then into central Kansas by mid day Monday. While
the track is agreed upon, there are still significant variations
in the details. At this time, overall confidence in timing and
location any of the embedded precipitation waves is low, but we
do anticipate at least a few periods of light snow backing to the
Front Range and I-25 corridor Sunday night in Monday morning with
a weak upslope component developing around the large circulation
center.

In the meantime, we should see snow become more widespread across
the eastern plains and Palmer Divide area Sunday night as the
bulk of Q-G lift arrives. The airmass is saturated with neutral
stability above 650-700 mb, so lift should be efficient in the
high precipitable water airmass (values over 0.50 inch on the
plains, which are in the 5 to 10 year return intervals for this
time of year). With regard to freezing rain threat, it appears
that potential into Sunday night may be decreasing as the expected
storm track is adjusted ever so slightly eastward, also slightly
reducing the penetration of the trowal into eastern Colorado.
Nonetheless, there is plenty of warm, moist advection over the top
of the cold dome so will keep some freezing rain and ice pellets
(sleet) in the forecast through the Sunday evening hours.
Thereafter, column cools sufficiently through vertical motion to
help change any mixed phase precip over to all snow. At this time,
main threat of any freezing precip would remain east of a line
from Sedgwick to Akron and Limon. Will keep the Winter Weather
Advisory in effect for moderate storm total snow accumulations
across the Palmer Divide, and then points eastward across portions
of the east central and northeast Colorado plains for moderate
snow accumulations and freezing rain threat. Expect lower
accumulations in the I-25 corridor with anywhere from a trace to 3
inches most likely at this time unless storm track deviates.

By Monday, storm system tracks off to the northeast. Morning snow
should taper from northwest to southeast with clearing skies
already expected by later in the afternoon. Northwest winds pick
up behind the storm system so areas that see a few inches of snow
on the eastern plains could see some blowing/drifting snow with
gusts to around 35 mph.

By Tuesday and Wednesday, upper level ridge axis will build over
the state with dry conditions and warmer temperatures. Should see
gusty chinook winds blow at times with increasing mountain top
stable layer and strengthening lee trough.

First wave in the next series of storm systems will help break
down the ridge toward Thursday, with some light snow expected to
move back into the high country. The latest GFS and and a few of
its ensembles show potential for a stronger, digging trough to
bring more snow to the forecast area by next weekend. Even the
ECMWF is carving out a large trough over the western United
States, so a return to unsettled and colder weather likely for
that period.

&&

.AVIATION...(For the 06Z TAFS through 06Z Sunday night)
Issued at 942 PM MST Sat Jan 14 2017

Light and variable winds and VFR conditions expected through the
remainder of the night...with light drainage winds expected by
13z.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory from 6 AM Sunday to 11 AM MST Monday for
COZ041-046-047-049>051.

&&

$$

UPDATE...Kalina
SHORT TERM...Kriederman
LONG TERM...Barjenbruch
AVIATION...Kalina



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