Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 130319
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
819 PM MST Thu Jan 12 2017

.UPDATE...
Issued at 803 PM MST Thu Jan 12 2017

Upper level moisture from the SW continues to stream over the
State. Earlier in the evening a cyclone set up with increasing
winds from the NNW that aided in bringing a trace to 1 inch of
snow across the Denver Metro. Temperatures have dropped into the
teens and lower 20s across the plains with snow turning light over
the high country. Snow will continue to diminish over the
foothills and northern plains through the evening. High levels of
mid level moisture will keep increased clouds over the region
overnight. Have been toying with fog early tomorrow morning and
have decided to leave patchy fog mainly over the South Platte
region SW into portions of the Denver metro and areas west of
I-25. This is mainly due to the amount of low level moisture even
without the added snowfall that was expected and light winds.
for Friday mostly cloudy conditions will remain with temperatures
staying in the 30s.

&&

.SHORT TERM...(This evening through Friday)
Issued at 257 PM MST Thu Jan 12 2017

Main weather concern revolves around snowfall potential across the
Front Range foothills and I-25 urban corridor this afternoon and
evening. There is a disturbance aloft in the southwest flow along
with a jet streak which will move over the area through this
evening. Surface cold front has already backed into the Front
Range and as consequently developed a strengthening denver cyclone
with stronger northerly winds developing over central and western
portions of the denver area. Precip is developing aloft based on
radar and snow should begin to fall between 3 and 430 pm over much
of the area. Still expecting light snowfall but high resolution
models are showing upwards of 3-6 inches along and West of the
interstate 25 Corridor due to stronger convergence due to the
Denver convergence zone. Given the snowfall will fall during the
evening rush hour will issue a winter weather advisory for the
Urban corridor. Front Range foothills should see 2 to 6 inches
before also ending later this evening.

Snowfall will diminish later this evening over the mountains and
adjacent plains. There is some fog potential later tonight and
early Friday morning due to the fresh snow on the ground and
continued cyclone over the Denver area.

.LONG TERM...(Friday night through Thursday)
Issued at 257 PM MST Thu Jan 12 2017

There is still some moisture streaming into the mountains through
Friday night, so still can`t say this snow cycle will end
completely. Any additional accumulation would be light though as
moisture depth, orographics, and lapse rates are marginal...and
any synoptic scale lift/jet dynamics shift eastward.

Attention for the weekend will then turn toward deep upper low
driving south into Baja. On saturday, this low should reach its
southern-most point south of the U.S./Mexico border before
gradually lifting northeast across the Southern Rockies. There is
still considerable uncertainty with regard to not necessarily the
path of the upper low, but the amount of negative tilt and extent
of precip shield back to the west. That tilt and shield is much
more amplified in the EC than the GEM, GFS, and most of the GFS
ensemble members. At this point, the forecast will maintain
consistency with a higher chance of snow over most of the
forecast area Sunday through Sunday night and Monday. There is so
much warm advection noted there is a chance of freezing rain over
the eastern plains which could produce significant disruptions to
travel from the eastern Colorado plains and points eastward into
Kansas. Will continue to keep a close eye on that potential, as
well as a narrow band of heavier snowfall on the deformation zone
as this storm kicks to the northeast into the Central Plains
states.

After that storm system, we will finally settle down to a couple
days of more tranquil, warmer, and dry weather Tuesday and into
Wednesday. The next in a series of storm systems may arrive into
the mountains by late Wednesday but more likely Thursday with more
snow in the high country.

&&

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 803 PM MST Thu Jan 12 2017

Snow has come to an end with MVFR conditions until 04 to 05z when
ceilings may lift above VFR. Continued mid level cloud deck
through most of the TAF period given increased mid level moisture
from the SW. Patchy fog will be possible from 11 to 15z with low
level moisture fields showing visibilities down to a mile or less.
I have medium confidence that this will occur given the mid level
cloud deck that will persist overnight. By tomorrow late morning
ceiling will lift with lower levels scattering out with VFR
conditions into Friday evening.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

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



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