Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 192313
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
413 PM MST Sun Feb 19 2017

.SHORT TERM...(This evening through Monday)
Issued at 349 PM MST Sun Feb 19 2017

Area radars show some showers over the mountains, but they are
light. There is nothing over the plains right now. Models push the
upper trough across the CWA overnight and then increasing
northwesterly flow aloft is progged on Monday. There is upward
motion on the QG Omega fields this evening for the CWA, then all
downward motion is progged overnight and Monday. Models all have
northwesterly low level winds after the upper trough passes this
evening. Downsloping winds are progged on Monday, weaker and
westerly over the foothills and western plains; stronger and
northwesterly over the eastern half of the plains. Moisture is
wide spread this evening and relatively deep in the mountains.
After the upper trough axis pushes across, things dry out
significantly. The QPF fields have some measurable precipitation
over the western half of the CWA this evening, then a tiny bit
more over the high mountains overnight, then nothing on Monday. So
for pops, 60-90%s look good in the mountains tonight, less in the
high valleys and foothills, down to 10-20%s over the plains
early. Although the winds could help with orographic enhancement
tonight in the mountains, by the time the directions get
favorable, the moisture is gone. There is no CAPE progged this
evening over the plains like there was yesterday on the 12Z models
for this evening. There is a decent looking mountain wave set up
on the cross sections tonight, but speeds don`t look high enough
for highlights. For temperatures, Monday`s highs will be 0-2 C
cooler than today`s highs.

.LONG TERM...(Monday night through Sunday)
Issued at 139 PM MST Sun Feb 19 2017

Monday night, the ridge axis will shift to the east with an
increasing westerly flow aloft over the region. The models show
some increase in moisture in the mountains west of the Continental
Divide but dry from The Front Range Foothills eastward. The
pattern will be the same on a slight chance of pcpn will be
possible in the mountains mainly north of Interstate 70. The
pattern will continue through the day on Tuesday. The NAM12
spatial cross-section shows a weak mountain wave developing around
12z Tuesday morning so gusty winds in the mountains and foothills
will be a good possibility. Could see some gusts to 50 mph over
exposed eastern slopes. Gusty winds will persist in the mountains
and foothills, with dry conditions with temperatures climbing into
the lower to mid 70s across the urban corridor and northeast
plains. The dry conditions will elevate the fire danger across the
northeast plains, refer to the fire weather discussion below.
Tuesday night/Wednesday, Pacific moisture increases in the
mountains below 600 mb so chc of pcpn will increase in the
mountains west of the divide, but persistent dry conditions with
gusty winds at time over the northeast plains. A weak front is
progged to back into the Urban Corridor around 18z Wednesday so
there will be a slight drop in temperatures on Wednesday, with
weak cold air advection aloft but temperatures will remain well
above normal. Wednesday night, a stronger southwesterly flow aloft
will be over Colorado with moisture increasing in the mountains
ahead of the next trough. Stronger cold air advection with the
next trough axis moves across northern CO on Thursday. Best chc of
accumulating snow in the mountains will be Thu/Thu night. Chc of
pcpn will carryover on the northeast plains, with the highest pops
across the northern tier counties. Cooler with a strong sfc
pressure gradient as the system exits the region Thursday night.
Short wave ridging and subsidence on Friday with continued cool
temperatures. Increasing moisture across northern and western CO
Friday night through Saturday night, as another system moves into
the Desert Southwest and is progged to lift northeast into CO late
Sunday/Sunday night.


&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 349 PM MST Sun Feb 19 2017

The south-southeasterly winds got into DIA, but speeds were
stronger than initially progged. winds should become northwesterly
after the upper trough axis moves across sometime mid to late
evening. I still think some sort of drainage pattern will
eventually win out before dawn Monday morning. There should be no
ceiling issues even though a few sprinkles are possible this
evening.

&&

.FIRE WEATHER...
Issued at 349 PM MST Sun Feb 19 2017

Winds come up fairly strong for the eastern plains Monday
afternoon, and humidity progs drop the RHs into the mid and upper
teens. The conditions will get close to RED Flag Warning criteria
over the eastern plains Monday afternoon, but no highlights for
now.

Unseasonably warm temperatures with relative humidities dropping
into the teens will be possible across the northeast plains of
Colorado Tuesday afternoon, elevating the Fire Danger. Stronger
winds will be in the foothills, but gusty winds over the Palmer
Divide could warrant a Fire Weather Watch at some point. The
threat will remain elevated on Wednesday but not as high as
Tuesday. Temperatures will remain above normal but will be
slightly cooler with a weak frontal passage Wednesday aftn.



&&

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

$$

SHORT TERM...RJK
LONG TERM...Cooper
AVIATION...RJK
FIRE WEATHER...Cooper



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