Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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000
FXUS65 KBOU 231751
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1051 AM MST Thu Feb 23 2017

.UPDATE...
Issued at 1039 AM MST Thu Feb 23 2017

Satellite and radar showing surge moving east over the foothills
and western plains. The upper jet...QG and upslope are providing
more seeder/feeder interaction along the higher terrain and
foothills allowing for more intense snowfall vs NE over the plains
with shallow conditions providing for freezing drizzle and light
snow. As the moisture continues to fill in from the NE and
deepens the freezing drizzle is expected to come to an end and
turn to snow for the remainder of the day. A strong boundary
pushed SW across the plains and area airports bringing visibility
down with snow. The mountains could see an additional
accumulation of 3 to 6 inches through Friday morning with a
couple inches possible for the urban corridor...most of it
falling under the more unstable band this afternoon. Models are
still showing a surge from the north bringing another round of
light snow overnight but in total Denver is still expected to see
1 to 2 inches with more to the north over the Wyoming border. Have
issued an advisory for the counties of NE
weld...Sedgwick...Philips and Logan counties until midnight with
upwards of 7 inches possible. A round of freezing drizzle this
morning could result in a layer of snow over the ice causing
hazardous conditions into tomorrow. Temperatures will not get much
above what it is currently given the continuous surge of cooler
air and moisture. Adjusted pops and temperatures to account for
increased for this.

&&

.SHORT TERM...(Today and tonight)
Issued at 507 AM MST Thu Feb 23 2017

Upper trough over Utah sliding east with large area of synoptic
scale lift from NE Utah/NW Colorado across Wyoming. This will
bring increasing snow to the mountains today, spreading along the
northern Colorado border as well. The strongest lift will be
north of the border, but with a sustained period of light to
moderate snow there should be an area of 1-3 inches of snow north
of about Fort Collins to Sterling and perhaps even more at the
state line. We will have to monitor just where this sharp gradient
winds up. The area of showers further south over SE Utah/SW
Colorado will eventually move over the central mountains and
should bring a round of snow showers across Denver in the late
afternoon and evening. This will be at the same time that north
winds will be increasing behind the surface low with cooling
temperatures. While the ground is warm to start the day, cool air
will remain in place so an inch or two of snow this evening could
still be enough to cause some travel issues around Denver.

Changes to the forecast include a general increase in PoPs as
confidence increases, with slight increases to the snowfall as
well, and adjustments to the timing mentioned above.

.LONG TERM...(Friday through Wednesday)
Issued at 507 AM MST Thu Feb 23 2017

Models have a mean upper trough over the western United States on
Friday. Flat upper ridging is over Colorado Friday night and
Saturday. Southwesterly flow aloft is progged Saturday night with
another upper trough to our west. The synoptic scale energy is
mostly downward in nature from Friday midday through Saturday
evening. For moisture, Friday looks cloudy. Moisture decreases
significantly across the CWA Friday night. On Saturday morning,
there is a tad lingering over the mountains. Later Saturday,
moisture increases substantially from the west. It is deep in the
mountains, with plenty in the mid and upper levels for the
plains. Models show Saturday night the same. The QPF fields have a
tad of measurable precipitation over the mountains Friday and
Friday evening, then again from later Saturday afternoon and
Saturday night. There is tiny bit progged over the plains Friday
morning into the early afternoon hours. For pops in the mountains,
will go with "likely"s early Friday, then "chance"s in the
afternoon and Friday evening. Will decrease pops to nothing early
Saturday, then increase them again by Saturday afternoon and night
to "chance"s. Snowfall amounts will be minimal. For the plains,
will go with "chance"s for snow Friday morning, then "slight
chance"s Friday afternoon, then dry after that. For temperatures,
Friday`s highs are 2-5 C colder than today`s highs. Saturday`s
highs only warm up 1-4 C over Friday`s highs. For the later days,
Sunday through Wednesday, models have a weak upper trough to push
across Colorado on Sunday. There is zonal flow aloft Sunday night
through Tuesday morning, then another upper trough moves across
through Wednesday morning. There is northwesterly flow aloft after
that. Sunday is pretty dry, but moisture increases Sunday night
with fair amounts in the mountains through Tuesday night.
Wednesday dries out. Temperature progs are not as warm on these
latest 00Z model runs as they were on yesterday`s for all four
days.

&&

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 1039 AM MST Thu Feb 23 2017

Surge of moisture from a boundary that tracked SW will bring lower
ceilings and visibility to KDEN...APA and BJC through the
afternoon with light snow and fog. With the moist NE flow
confidence is low that conditions will improve to MVFR without
much mixing. Expect IFR conditions to prevail through 12z Friday.
Winds will remain from the NE with speeds of 5 to 10 mph before
switching to north with frontal surge along with another round of
snow. Snow fall intensity should stay light without much in the
way of upper level dynamics.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until midnight MST tonight for COZ042-
048-050-051.

Winter Weather Advisory until 9 AM MST Friday for COZ031-033.

&&

$$

UPDATE...Bowen
SHORT TERM...Gimmestad
LONG TERM...RJK
AVIATION...Bowen



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