Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 080416
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
916 PM MST Thu Dec 7 2017

.UPDATE...
Issued at 849 PM MST Thu Dec 7 2017

The area radars are showing the batch of flurries and light snow
is moving south and decreasing over the CWA right now. There is
still some snow over the Palmer Ridge, southern foothills and Park
country. There is little precipitation upstream. Will update the
sky, weather and pop fields according to real data.

&&

.SHORT TERM...(This evening through Friday)
Issued at 230 PM MST Thu Dec 7 2017

Light snow is occurring over the mountains, and should continue
through this evening as another wave of moisture moves in from the
north. That is supported by the latest IR imagery showing colder
cloud tops and radar imagery with light echoes becoming more
widespread across Wyoming. On the plains, some virga around this
afternoon, but with next wave of moisture will keep some low PoPs
into the evening. Palmer Divide still has the main chance of
seeing any light snow accumulations where orographics are more
favorable. Elsewhere, a downslope component exists across the
plains so once the next wave of moisture moves through skies
should begin to slowly clear.

Lows tonight will be several degrees warmer with warm advection
and a downslope component in place. Any inversions should be
pretty weak with some wind holding in place through the night. On
Friday, warm advection continues so high temperatures on the
plains will push back into the 50s. Gusty winds will also develop
during peak heating and daytime mixing. Speeds of 20-35 mph will
be common east of I-25, with gusts reaching 50 mph on the eastern
plains and northern border area. The strong winds combined with
warmer temperatures and low humidities will create high grassland
fire danger...see Fire Weather section.

.LONG TERM...(Friday night through Thursday)
Issued at 230 PM MST Thu Dec 7 2017

Large blocking upper ridge will continue to bring prolonged dry and
warm conditions to the region. Moderate NW flow aloft will mix down
Friday into Saturday bringing increased winds to the plains. By
Friday evening the strong winds on the plains will start to
dissipate but gusts from the NNW with speeds of 20 to 30 mph will
still be possible into early Saturday. Temperatures will quickly
rebound back to above normal with highs on Saturday reaching into
the lower 60s. For Sunday the upper ridge will deepen and push west
increasing pressure and temperatures with up to 20 degrees above
normal possible.

For the start of next week models show some weakening in the western
ridge with a jet max dropping SE associated with a trough. The
placement of the trough is not in total agreement with various
models but is moisture-starved so only expecting some increased
winds on the plains and a slight drop in temperatures Monday
afternoon. Temperatures will rebound on Tuesday in a big way with a
lee side low helping to increase downsloping winds and highs in the
low to mid 60s.

By Wednesday a slight pattern shift is possible with the ridge
breaking down and slipping south. This will allow for NW flow to
increase and drop a disturbance down into CO. Models are not in
current agreement with timing with the EC roughly 6-12 hours behind
the GFS. Will have to wait and see how models are initialized in the
days to come.

&&

.AVIATION...(For the 06Z TAFS through 06Z Friday night)
Issued at 849 PM MST Thu Dec 7 2017

Drainage winds are blowing at DIA right now. Some of the models
show northwesterly winds all night at the airport. I will stick
with a drainage/southwesterly mix. As far as ceiling issue go; a
few observations upstream show some SCT-BKN050. The precipitation
should be over.

&&

.FIRE WEATHER...
Issued at 230 PM MST Thu Dec 7 2017

Fire danger will increase on Friday with strong, gusty winds
overspreading the plains. Humidities will be marginal, but the
extremely dry fine fuels and grassland fire danger will warrant a
Red Flag Warning for late morning through the afternoon.
Combination of the strongest winds and lowest humidities east of
I-25. Far northeast corner has slightly higher RH, but grassland
fire danger will still be elevated.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning from 10 AM to 5 PM MST Friday for COZ238-
241>249.

&&

$$

UPDATE...RJK
SHORT TERM...Barjenbruch
LONG TERM...Bowen
AVIATION...RJK
FIRE WEATHER...Barjenbruch



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