National Weather Service National Headquarters

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

000
FXUS65 KBOU 181634
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1034 AM MDT Mon Sep 18 2017

.UPDATE...
Issued at 1003 AM MDT Mon Sep 18 2017

No significant updates planned in today`s period but
reference the fire weather discussion below regarding the
upgrades and expansions planned for the fire weather
highlights for Tuesday.

&&

.SHORT TERM...(Today and tonight)
Issued at 420 AM MDT Mon Sep 18 2017

The water vapor pictures are showing a weak upper trough moving
across the CWA right now. Radars are showing a batch of light rain
showers over the eastern half of the plains right now. They are
moving northeastward. Satellite pictures are also showing it to
be quite clear in the immediate upstream. no measurable
precipitation on the QPF fields today or tonight. Models have
fairy weak west-northwesterly flow aloft for this morning. By
later this afternoon and tonight, weak west-southwesterly flow
aloft is expected. The QG Omega fields show benign synoptic scale
energy for the forecast area today and this evening, then upward
motion moves in later tonight ahead of an approaching upper
trough. The boundary layer winds should be weak and downsloping
this morning. Southeasterlies are progged later this afternoon and
evening, with normal drainage flow tonight in most areas. For
moisture, it continues to dry-out through today and tonight.
Precipitable water values are in the 0.10 to 0.50 inch range from
west to east across the CWA by later tonight. There is a tad of
weak CAPE around early tonight, then nothing later and overnight.
Lapse rate fields on the cross sections show a fairly strong
stable layer around 600 mb today and tonight. It will be dry and
subsident. Once the few showers over the east move out we will
need zero pops today or tonight. For temperatures, today`s highs
will be 4-8 C warmer than Sunday`s.

.LONG TERM...(Tuesday through Sunday)
Issued at 300 AM MDT Mon Sep 18 2017

WSW flow aloft will increase on Tue as an upper level trough moves
across the nrn Rockies Tue aftn and night.  There will be some
moisture over the higher terrain nr the WY border late in the aftn
thru Tue evening.  There will be a quick shot of mid lvl ascent in
this areas as well so will keep in a chc of pcpn in the mtns nr the
WY border.  Over the rest of the area it will be dry with abv normal
temps as readings range fm the mid 80s to around 90 over nern CO.
Meanwhile a pacific fnt will move across the nern CO in the evening
so there will probably be a period of gusty winds with this feature.

On Wed dry WSW flow aloft will be over the area with no pcpn
expected.  Temps will not be as wrm across nern CO as highs will be
in the upper 70s to lower 80s.  For Thu an upper level trough will
intensify over the wrn US with increasing SSW flow across nrn CO.
Once again there will not be much moisture around so expect it
will be dry thru the aftn. Meanwhile temps will wrm back into the
mid 80s to around 90 across nern CO.

For Fri the upper level trough will move slowly eastward with stg
SSW flow aloft remaining over the area.  Both the ECMWF and GFS show
some moisture embedded in the flow and as a disturbance moves across
wrn CO this would lead to a chc of showers over the mtns.  Over nern
CO there is still quite a bit of uncertainly regarding whether a
fnt will move across the plains or not. With the main upper level
trough still centered to the west, my gut feeling is that it will
still reside to the north leading to another dry and warm day
across the plains.

By the weekend the upper level trough is fcst to slowly move across
the area as a cold front moves across nern CO on Sat.  This should
lead to an unsettled ptrn with much cooler temps.

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1003 AM MDT Mon Sep 18 2017

Southwesterly winds this morning at KDEN still expected to switch
to southeasterly by 19-20z, then normal drainage patterns by 03Z
this evening. There will be no ceiling issues.

&&

.FIRE WEATHER...
Issued at 1003 AM MDT Mon Sep 18 2017

The fire danger will increase later today and again on Tuesday
due to above normal temperatures and increasing wind. The plan is
to upgrade the Fire Weather Watch to a Red Flag Warning for
the Front Range Foothills, Middle Park, South Park, the north
central mountains around Summit County, the Palmer Divide,
eastern Larimer and northwest Weld County from 1100-2000 mdt
Tuesday. In addition we will be including the adjacent plains
areas in a Fire Weather Watch for the same time. Highest
confidence will be in the warning area where warm temperatures, rh
values in the teens and gusty winds are expected. Not as
confident in the wind potential in the watch area but the other
critical factors are there which is why we have included those
zones in a Fire Weather Watch.

The elevated fire danger is possible Wednesday and Thursday as
well.

&&


.BOU WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning 1100-2000 mdt Tuesday for
COZ212>216-238-241-246-247.
Fire Weather Watch 1100-2000 mdt Tuesday for
COZ239-240-242>245-249.
&&

$$

UPDATE...Cooper
SHORT TERM...RJK
LONG TERM...RPK
AVIATION...Cooper
FIRE WEATHER...Cooper/Meier