Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29

FXUS65 KBOU 171604

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1004 AM MDT Mon Oct 17 2016

Issued at 949 AM MDT Mon Oct 17 2016

Showers associated with passage of the upper level jet already
slipping into the foothills of Larimer County so have sped up the
timing for showers in that area today. Latest HRRR starts the
cold front into the Denver area by 21z. Should see gusty
west/southwest winds ahead of the front with north/northwest winds
following fropa. Strongest wind gusts in the mountains today
appear to be this morning. No changes to the current highlights at
this time.


.SHORT TERM...(Today and tonight)
Issued at 440 AM MDT Mon Oct 17 2016

Usually strong Pacific jet stream for this time of year currently
draped across the central Great Basin is projected to rapidly
extend eastward acrs wyoming and extreme northern Colorado through
the day. At the core of this jet are 140+ kt wly winds. Strong
subsidence and especially dry air along the south side of this jet
were largely responsible for the nearly cloud free skies over the
state at the present time. As this jet core nears the area should
see a fairly dramatic increase in winds esply over higher
elevations of the Front range Mtns. A high wind warning has
already been issued for this area. Next the very dry conditions
coupled with steadily increasing westerly winds have prompted a
red flag warning for the foothills and plains. Have gone ahead and
added the mtn valley zone 213 (Middle Park) to the warning since
current RH and wind readings already nearly red flag criteria at
this early hour. I was considering adding fire weather zone 211
(North Park) but models continue to generate cloud cover...higher
RH and at least a slight chance to wetting rainfall this afternoon
with passage of a weak mid-level disturbance which models show racing
along the jet. East of the mtns...models continue to show a cold
front dropping out of Wyoming and across northeast Colorado mid
to late afternoon. Possible we could see a shift to north-
northeast winds before it arrives which would explain the cooler
guidance temperatures today. With frontal passage could see north-
northwest winds gusting in the 30-45 mph range for a few hours on
the plains. Strongest speeds appear to stay east of the I-25
corridor...expect up near the Wyoming border where even stronger
may occur. Highs today roughly 10 to 15 degs f lower than those
yesterday. No records broken today. Tonight...should see winds
letting up through the evening as cooler air filters down from
Wyoming. Showers chances in the high country should fall below 10
percent not long after sunset with drier air moving in. Should
also see wind speeds dying down everywhere as the core of the jet
weakens and shifts northward away from the forecast area.
Overnight lows as much as 10-12 deg f lower...about where they
should be this time of year.

.LONG TERM...(Tuesday through Sunday)
Issued at 440 AM MDT Mon Oct 17 2016

An upper level trough will approach the area Tue aftn and then move
across Tue night into early Wed.  Moisture will gradually increase
in the mtns by Tue aftn and become deeper Tue Night with orographics
becoming more favorable.  In addition with some mid lvl QG ascent
and position of upper level jet will see a good chc of snow in the
mtns especially along and north of I-70.

Over nern CO it will be dry thru Tue aftn with cooler temps as highs
will be in the 60s.  By Tue evening a cdfnt will move across the
plains with nly low lvl flow.  As main part of upper level trough
moves across Tue night and associated mid lvl ascent would think
there would still be a chc of showers fm the nrn Foothills across
portions of nern CO mainly north of a Denver to Fort Morgan to Akron
line. Further south pcpn chances look lower fm the srn Foothills
across the ecntrl plains.  Temps may become cold for a rain...snow
mix nr the WY border late Tue night.

On Wed the upper level trough will quickly move eastward with
decreasing moisture thru the morning hours.  Thus pcpn chances
should diminish across the area.  Highs on Wed will range from 55 to
60 degrees across nern CO.  By Thu dry nwly flow aloft will be over
the area with seasonal temps.

For Fri thru next Weekend an upper level ridge will be in place with
dry conditions and a warming trend as highs reach the 70s across
nern CO.


.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 949 AM MDT Mon Oct 17 2016

south/southwest winds this morning should start to transition to
westerly by 18z. The cold front is still expected to move into the
Denver area around no changes to the current tafs.
Otherwise VFR with no restrictions. Lower levels will remain dry
so no showers expected with the passage of the cold front.


Issued at 440 AM MDT Mon Oct 17 2016

Red flag warning remains in effect for the plains...foothills and
South park fireweather zones. Have added the mountain valley zone
213 (Middle Park) to the warning because near red flag warning
conditions already exist up there at this hour. These conditions
should improve first in the mtns and then on the plains this
evening as colder and more humid air filtering in from the north
behind a cold front which is expected to drop south through the
area mid to late afternoon.


Red Flag Warning until 9 PM MDT this evening for COZ213>216-

High Wind Warning until 4 PM MDT this afternoon for COZ033-034.



FIRE WEATHER...Baker is the U.S. government's official web portal to all federal, state and local government web resources and services.