Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 201747
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1047 AM MST Mon Feb 20 2017

.UPDATE...
Issued at 1020 AM MST Mon Feb 20 2017

have dropped the pops in the mountains for the rest of the
morning. Otherwise sunny and dry with only minor adjustments to
the grids. Gusty winds will continue in the mountains. Elevated
fire danger across the plains this aftn, main concern will be the
far eastern zones where some gusts to 35 mph will be possible
through early aftn, but then the stronger gusts are expected to
lessen the rest of the aftn. Reference the fire weather discussion
below.


&&

.SHORT TERM...(Today and tonight)
Issued at 343 AM MST Mon Feb 20 2017

The short wave trough responsible for light rain showers across the
Plains and a welcome snow to the ski country Sunday night into early
this morning continues to shift east into the Central Plains.
Moisture and instability has decreased quite a bit as the trough
axis pulls away from Colorado.  The last of the light sprinkles will
exit NE Colorado in the next hour or so. Expect the snow to end
in the mountains by about 9 AM.

Today Colorado will be on the backside of the trough with dry NW
flow aloft. A flat ridge with synoptic scale subsidence will
result in partly to mostly sunny skies and continued well above
normal temperatures across much of the CWA. 700 mb temperatures
are similar to Sunday`s and there is neutral temperature advection
occurring throughout the day today and overnight into Tuesday.
Thus, expect high temps across the Plains in the low to mid
60s.Winds across the Plains will also be strong out of the
northwest (20-25 mph with gusts to 30 mph) this afternoon given a
tight pressure gradient between the surface high across W.
Colorado and low across the Northern Plains of the U.S. Mountains
will be in the 40s, though North Park and the snow cover there
should keep temps in the 30s. Above 9000 feet temps should also
stay in the 30s. Overnight lows Tuesday morning will be above
normal with mid 30s across the Plains, though in and near the
foothills lows will remain in the mid and upper 40s with downslope
winds blowing all night and increasing after 3 AM or so.

In addition to keeping min temperatures Tuesday morning up in and
near the foothills, the intensity of the winds will lead to elevated
Fire Weather conditions from the foothills east to the Plains.
Please see Fire Weather Discussion below for details. Models are
indicating favorable conditions for a mountain wave to set up early
Tuesday morning with a strong potential temperature trough
downstream of the Continental Divide, and flow at ridge tops out
of the West at 40-50 kts. Models differ on the stability of the
layer at and above 650 mb however. Still think that gusts 50-60
mph are possible from the ridge tops down to favored locations
near the foothills.

.LONG TERM...(Tuesday through Sunday)
Issued at 343 AM MST Mon Feb 20 2017

Wly flow aloft will increase across the area on Tue with stg
downslope flow in the lower levels.  Will see gusty winds across the
higher terrain spreading across the plains during the day.  Hi-Res
WRF shows some potential for high winds thru 15z Tue in and nr the
Foothills with some gusts near warning criteria.  Gusts across the
plains will range from 30 to 40 mph with the higher speeds nr the WY
border.  With downslope warming aftn highs will rise into the 70s
over nern CO with record high of 71 at Denver likely being broken.
In the mtns there will be some moisture affecting the far nwrn mtns
in zn 31 so will keep in some low pops.

For Tue night into Wed the flow aloft will become more wsw with
gusty winds continuing across the higher terrain.  Cross-sections
continue to show some moisture affecting the mtns mainly mainly
north of I-70.  With upper level jet over the area could see some
enhancement of pcpn especially in zn 31 with favorable wsw flow so
will mention likely pops with sct pops in zn 33.  Over nern CO a sfc
low will dvlp over sern CO on Wed as a wk fntl bndry move across the
plains by aftn.  Thus aftn highs will not be as wrm with readings
in THE 60s across most of nern CO except for lower to mid 70s
over srn Lincoln county. Winds will remain gusty over the plains
esp nr the WY border and over the Palmer Divide.

By Thu an upper level trough will move across the area with a decent
shot of mid lvl QG ascent along with favorable lapse rates.  Thus
this will bring a good chance of snow to the mtns.  At lower
elevations a sfc low will be over sern CO/swrn KS as a cold fnt
moves across nern CO.  The last few days the ECMWF and GFS have had
varying solutions as to how much moisture there will be over nern
CO. With the fnt moving across early in the day with upslope flow
developing, hard to believe there won`t be some pcpn across nern
CO especially in the aftn into the evening hours, as mid lvl
ascent affects the area. As for highs readings will likely occur
before noon and then fall thru the aftn.

For Thu night into early Fri both the ECMWF and GFS show a possible
disturbance moving across in wnw flow which will bring more snow to
the mtns. Across nern CO there could be a chc of light snow as
well especially if the wetter ECMWF verifies. By Fri aftn into Fri
night the ECMWF shows drier air spreading across in wly flow
while the GFS shows an increase in moisture. With an upper level
jet being over the area if there is enough moisture around could
see some banded pcpn based on the GFS solution so this will be
something to watch the next few days. As for highs on Fri readings
will stay in the 30s over nern CO.

On Sat the flow aloft will stay mainly wly with some moisture
embedded in the flow so will keep a chc of snow in the mtns.
Across nern CO it looks dry with highs in the 35 to 40 degree
range. For Sat night into Sun an upper level trough is fcst to
move across the area which will bring more snow to the mtns.
Across nern CO there could be a chc of snow as well Sat night into
early Sun with temps remaining blo normal.

&&

.AVIATION...(For the 12Z TAFS through 12Z Tuesday morning)
Issued at 1020 AM MST Mon Feb 20 2017

VFR conditions through Tuesday. Winds will be NW at 6-12 kts this
afternoon at DEN and APA. BJC dealing with light and vrb winds
this morning, could see westerly component up to 10 kts return in
the aftn. Tuesday morning, stronger winds expected at all
terminals but especially at BJC. Winds at BJC will increase after
09Z, while APA and DEN should have typical drainage winds develop
after 03Z, then stronger winds after 15z Tuesday morning as the
westerly winds kicks in.


&&

.FIRE WEATHER...
Issued at 1020 AM MST Mon Feb 20 2017

Elevated fire weather conditions will occur this afternoon across
the eastern plains roughly east of a line from Cheyenne WY
southeast to Lincoln County, CO. Opted not to issue a RFW for this
area as conditions are marginal for 4-5 hours between noon to 4
PM. Nevertheless, conditions are favorable for rapid brush fire
growth given NW winds 15-25 mph with higher gusts and relative
humidity values in the teens this aftn. The stronger gusts
however should start to lessen across the northeast plains after 2
pm. Dry in and near the foothills as well but wind has tapered
off this morning however low relative humidity values, warm
temperatures, dry/dormant fuels will keep the fire danger elevated
there this aftn. Although not as strong gusty winds may occur at
times this aftn.

Fire danger higher and more widespread across the foothills and
adjacent plains on Tuesday due to gusty winds...low humidity and
possible record high temperatures so a Fire Weather Watch has
been issued for the afternoon and early evening hours.

Fire danger will remain elevated for Wednesday although winds may
not be as strong across the plains but will remain gusty in the
foothills.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Fire Weather Watch from Tuesday afternoon through Tuesday
evening for COZ215-216-238>251.

&&

$$

UPDATE...Cooper
SHORT TERM...Schlatter
LONG TERM...RPK
AVIATION...Cooper
FIRE WEATHER...COOPER/RPK



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