Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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570
FXUS65 KBOU 241608
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
1008 AM MDT Mon Apr 24 2017

.UPDATE...
Issued at 1008 AM MDT Mon Apr 24 2017

A short wave trough will move over the Great Basin later today.
This will cause clouds to increase this afternoon. Rain and
mountain snow is expected to move into the high country late this
afternoon with the approach of this system. Best lift will move
from north to south tonight across the area as this wave pushes
across the region and a jet sinks south.

North to northwest winds are gusting to 40 mph over the northeast
plains at this time. Expect winds to decrease early this
afternoon as the pressure gradient slackens. On the west edge of
these northerly winds, the winds are turning northeast and are
expected to turn easterly after 18z. The RAP and HRRR models show
a westerly push off foothills this afternoon. Convergence along
this westerly push may trigger isolated showers and storms around
21z. This convergence area may end up farther west than the models
are showing. The HRRR has a history of mixing westerly winds down
too soon and spreading them too far east. Will have low pops for
this afternoon along the Front Range and across the eastern
plains for this convection. There will be a better chance for rain
showers tonight when the best lift will be over the area.

&&

.SHORT TERM...(Today and tonight)
Issued at 302 AM MDT Mon Apr 24 2017

Water vapor imagery showing weak disturbance moving across the
northern mountains of colorado now and associated cold front
sweeping southward across the eastern plains. This is a quick
moving system and will expect mountain showers to diminish by
daybreak. Also seeing some increase in gusty winds over the
mountains and foothills with speeds up to 50 mph. Temperatures
will be cooler today on the plains behind the cold front but
still pleasant with readings near 70.

With increasing westerly flow will see next upstream system to
quickly approach Colorado this afternoon and then move over
Wyoming tonight with another shot of snow for the mountains and
even a chance for showers over the plains, especially near the
Wyoming and Nebraska border areas. Current forecast has this
handled well with increasing pops in the mountains by later this
afternoon and evening. Expect some light snow accumulations in
the mountains from this afternoon and especially tonight with
improved orographic flow. Could see 2-4 inches in the mountains
in the tonight period.

.LONG TERM...(Tuesday through Sunday)
Issued at 302 AM MDT Mon Apr 24 2017

...An active pattern will bring periods of rain and snow and
cooling temperatures through the week and weekend...

The first of three main systems will impact the area Tuesday.
Decreasing heights aloft and a surface low over southeastern
Colorado will allow for cooler temperatures to filter in during
the day, before a strong push from the north brings northerly
winds of 20 gusting to 30 mph and colder temperatures. Moisture
associated with this system will both affect the high country and
the plains, though downsloping off the Cheyenne Ridge will likely
keep PoPs lower just south and into the Denver area for most of
the day but increase them over the Palmer Ridge. Upward QG motion
will maximize south of the forecast area, thereby focusing the
greatest potential for moderate to heavy amounts south as well.
Snow levels during the day should be around 7000 feet, then forecast
soundings show the potential for snow to mix in along the urban
corridor and adjacent plains that evening, although chances of
precipitation will be moving south out of the area. Could 2 to 6
inches over the higher mountains, mainly east of the Divide, and see
a trace to up to 2 inches south of the Denver area up over the
Palmer Ridge and east across the plains of Elbert and Lincoln
counties. Precipitation will diminish towards Wednesday morning.

The next system to impact the area will push in on northwesterly
flow aloft Wednesday evening with an upper low dropping over the
northern Rockies by Thursday. This will be increasing snow across
the mountains through Thursday morning, with snowfall amounts
looking to be in the 3 to 8 inch range. There may be a few
showers that make it out over the urban corridor and northern
plains Wednesday afternoon and early evening, but not expecting
much. A slightly better chance of showers will occur Thursday as
another cold front pushes down.

The upper low over the northern Rockies will then dig further
south to the Four Corners area by Friday evening. Northern Pacific
moisture will be moving in with this system along with colder
temperatures. Low level moisture will also move up from the Gulf
to add to the precipitation potential. Models have been slow to
converge on a solution, but at this point, moderate rain and snow
is expected for the area, especially east of the divide, with
snow levels dropping down to the plains likely occurring by
Friday evening and into Saturday. High temperatures Saturday may
stay in the low to mid 30s, though this will depend on the low`s
track. GFS is digging it further south and slowing it down, while
the EC is quicker and further north, with the GEM splitting the
difference. Will have temperatures in the mid 30s for Saturday and
precipitation decreasing that evening. Saturday night could bring
hard freezing temperatures if skies clear. Northwest flow aloft
is expected for Sunday and Monday, with slowly warming
temperatures but precipitation likely still in the forecast with
several impulses still being forecast.

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 1008 AM MDT Mon Apr 24 2017

Clouds will increase after 18z as an upper level system moves
over the Great Basin. Ceilings are expected to remain above 6000
feet through 00Z. There will be a slight chance for a thunderstorm
from 21Z to 03Z, about a 10 to 20 percent chance, so will not
mention in the TAFs. Ceilings will lower around 00Z and may end up
around 6000 feet for a short time around 00Z to 03Z.

There will be slight chance for low clouds with ceilings less than
1000 feet after 06Z. Best chance will be over the eastern Colorado
plains and east of the Denver area. Will mention few at 1000 for
the slight chance of low ceilings tonight.

Winds are expected to be light through the next 24 hours in the
Denver area with a wind direction from the north to the east.

&&

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

$$

UPDATE...Meier
SHORT TERM...Entrekin
LONG TERM...Kriederman
AVIATION...Meier



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