Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 152046
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
246 PM MDT Sun Apr 15 2018

.SHORT TERM...(This afternoon through Monday)
Issued at 1131 AM MDT Sun Apr 15 2018

Weather is expected to be warmer and drier through Monday with
high pressure aloft. GOES 16 satellite shows high clouds moving
across the Great Basin which will spread east over the Colorado
Rocky Mountains through the day.

On Monday high temperatures will be about 10 to 15 degrees F
warmer than today. A deepening surface trough over the Front Renge
Foothills will lead to winds up to 25 mph over the plains during
the afternoon and evening.

.LONG TERM...(Monday night through Saturday)
Issued at 1131 AM MDT Sun Apr 15 2018

Monday night, a increasing southwesterly flow aloft will be over
Colorado ahead of the next system, moving into western UT. The
models show weak moderate mid level qg ascent developing after
06z. NAM12 spatial cross-sections show a short lived amplified
mountain wave profile in the 06-09z window. Stronger winds would
impact the east slopes of the Front Range Mountains and higher
foothills, with some gusts around 60 mph. Overall, the airmass
appears to be fairly dry over most of the cwa except zones 30>32.
Tuesday and Tuesday night, the trough axis is expected to move
across the cwa. Strong but fairly brief mid level qg ascent will
be present near the CO/WY border at 18z Tuesday, then strong
downward subsidence kicks in the late afternoon and evening
period. In the mountains, southwest wind level winds will switch
to the northwest. Light to moderate snowfall will be possible,
with potential amounts in the 3-6 inch range. Across the northeast
plains, gusty southwest winds will be present in the morning,
especially along the Palmer Divide then stronger west/northwest
winds will spread across the northeast plains with the passage of
the cold front on or after 21z in the afternoon. Bora type of
winds with good mid level instability, subsidence and cold air
advection helping to mix the stronger winds to the surface. Not
thinking highlights at this time, but could see gusts in the 45-55
mph range during the late aftn/evng period. Wednesday and
Thursday, a ridge of high pressure will shift over the state with
the mid level axis over central CO around 00z Thu. In the
mountains, some residual orographic snow showers along the west
facing slopes early then dry. Over the northeast plains, could see
some gusty northwest winds over the far northeast plains, with a
lighter north/northeast wind component over the rest of the lower
elevations. Wednesday night into Thursday, the ridge axis shifts
to the east with an increasing southwesterly flow developing over
the region in the afternoon ahead of the next storm system. Gusty
southwesterly winds will develop in the mountains by that time,
with southerly winds increasing across the northeast plains. This
should result in some moderation in temperatures from Wednesday to
Thursday.

The next potential impact for much of the cwa will occur in the
Friday to Saturday period.  The models all show a closed upper
trough over the Great Basin Thu aftn, intensifying and shifting
eastward across southern CO by midday Friday.  This type of
system could provide sustained and deep easterly upslope and
widespread precipitation as it advects moisture from the
Gulf of Mexico into eastern CO.  The eastward progression of the
trough appears to slow down Friday afternoon and Friday night which
would also help to produce moderate to heavy snow/rain.
This would result in heavy snowfall for the mountains and foothills,
with a mix of snow/rain across the eastern plains.  There are some
timing/track issues however that crop up at that point.  The GFS
keeps the sfc and upper low in a more favorable location of
southeast CO midday Friday, while the ECMWF is further west with the
upper low and further south with the sfc trough. This would shift
the focus into southeast CO.  Too many details to get caught in the
weeds with at this time.  For now will maintain likely pops in the
grids, especially from the Front Range eastward across the plains.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 1131 AM MDT Sun Apr 15 2018

VFR conditions are expected today through Monday. Winds will
continue to be light this afternoon. Typical drainage winds are
expected later tonight.

&&

.FIRE WEATHER...
Issued at 1131 AM MDT Sun Apr 15 2018

On Monday there will be near red flag conditions across the Palmer
Divide with some gusty winds expected. Due to the short duration
for these conditions, there will be no highlight issued at this
time.

On Tuesday fire danger will increase over South Park, the Foothills
and along the Front Range extending southeast towards the Limon
area. This will be due to expected very windy conditions ahead of
and behind a Pacific front and low humidity values. Consequently a
Fire Weather Watch has been issued for the following fire weather
zones listed below.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Fire Weather Watch from Tuesday morning through Tuesday evening
for COZ241-245>247.
&&

$$

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


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