Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 300222
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
822 PM MDT Sat Apr 29 2017

.UPDATE...
Issued at 811 PM MDT Sat Apr 29 2017

The trend for this evening and overnight is for diminishing
snowfall from northwest to southeast over the plains. Already
some indications that this is occuring as radar reflectivity is
beginning to decrease/end over Larimer and Weld counties and this
will also translate south and east over the plains by later
tonight. The strong upper low will continue to ever so slowly
shift east in into North central Texas tonight. Main change to
forecast was to delay the ending of the snow this evening.

Main concern for tonight is cold temperatures dropping into the
20s over the plains tonight. Still lingering cloud cover might
keep temperatures a bit higher especially over far ne Colorado
where temperatures are still in the upper 30s/lower 40s. Will
maintain the freeze warning across lower elevations.

&&

.SHORT TERM...(This evening through Sunday)
Issued at 312 PM MDT Sat Apr 29 2017

Nice back edge deformation band just now forming across the
eastern plains as north winds are bringing drying along the Front
Range, and lift around the back edge of the large storm continues
to increase over eastern Colorado. It looks like Denver will be
right on the back edge of this into early evening, then this will
slowly move eastward. We will still need to watch Lincoln and
Washington counties and the Holyoke area to see if they need more
snow, but so far our forecast has been a little high and impacts
appear to be minimal. But the heaviest snow of the event in those
areas may be over the next 6 hours.

Given the current trends, we will drop the western part of the
Winter Storm Warning and keep it for eastern Elbert and Lincoln
counties.

The other issue is cold temperatures tonight. We`re getting lots
of help from the slower storm motion--slower clearing, more wind,
and lots of moisture at the surface. There will still be some
clearing over the western part of the area later tonight and even
with the other factors it will be more than a little below
freezing. There will probably be some upper teens/lower 20s in the
coldest spots that clear--most likely Weld county river valleys.
Most of the area will probably stay in the mid to upper 20s
though. We will go ahead and issue a freeze warning for all of the
plains to alert people to the colder temperatures Sunday morning.

Sunday will see continued gradual clearing along the eastern
border. The timing of this continues to gradually slow. Further
west some mid level moisture and a little instability comes into
the mountains at peak heating, so the isolated showers still look
good there. Increased the winds a bit more on the plains as we
will have 30-40 knot flow not far off the ground. Probably a bit
less near the Front Range.

.LONG TERM...(Sunday night through Saturday)
Issued at 312 PM MDT Sat Apr 29 2017

Sunday night a moderate to strong northwesterly flow aloft will be
over the region with an upper level jet around 95 kts translating
across the state. Mid level subsidence associated with weak
ridging aloft. Enough moisture to produce some light orographic
snowfall a favoring the mountains mainly north of I-70. On Monday,
could see some convective showers develop with the passage the
upper level jet across the northeast plains as well. A strong
northwesterly flow continues over the state Monday night and
Tuesday, then another weak trough embedded in the flow aloft drops
out of the northern Rockies and brushes across the state. Neutral
to weak qg ascent aloft Monday night and Tuesday, then moderate
ascent developing Tuesday night and Wednesday with the passage of
the upper level trough. Favorable orographics and mid level cold
air advection will allow for another round of accumulating
snowfall in the northern mountains and higher foothills,
somewhere in the 3-8 inch range, with rain showers across the
northeast plains. The snow level by 12z Wednesday could drop to
around 5500 feet, so a rain/snow mix likely over the Cheyenne and
Palmer Ridges. A cold front associated with the trough is progged
to push across the cwa Tuesday evening, with a cooler airmass
continuing across the northeast plains of CO through Wednesday. A
ridge of high pressure will bring dry and warmer weather to the
region for Thursday through Saturday. The ridge axis is progged to
shift to the east by the weekend with the flow aloft becoming
southwesterly. Enough mid level moisture at that time coupled with
temperatures in the mid to upper 70s to produce a slight chance
of tstms in the aftn.

&&

.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 811 PM MDT Sat Apr 29 2017

Already seeing some improving conditions in ceilings at kden with
diminishing snowfall to the north. Light snow will end by 04z at
KDEN and then by 06z at APA with VFR returning after midnight.
Still see mid level clouds so fog development looks low.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Freeze Warning until 8 AM MDT Sunday for COZ038>051.

&&

$$

UPDATE...Entrekin
SHORT TERM...Gimmestad
LONG TERM...Cooper
AVIATION...Entrekin



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