Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 212028 CCA
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
225 PM MDT SUN AUG 21 2016

.SHORT TERM...(This evening through Monday)
Issued at 225 PM MDT Sun Aug 21 2016

Flat upper ridge over Colorado tonight will shift east of the
state on Monday as a wave of mid-level energy and moisture lifts
northeastward over the Four Corners region. This shortwave is
rotating around a broad weakly organized upper trough over the
southwest U.S. which models show migrating slowly eastward during
the forecast period. The gusty high based t-storms drifting across
South Park and topping the high terrain circling the Park should
dissipate not long after sunset due to the lack of support aloft.
Dry and stable conditions will then dominate the CWA overnight
with a light downslope gradient flow on the plains. Looking for
lows tonight to be near to slightly above average for the date.

On Monday...should see mid and high-level moisture spreading
northeastward over the forecast area during the morning in advance
of the shortwave advancing over southwest Colorado. NAM and GFS
handle this feature similarly...while the ECMWF indicates a drier...
less organized system. Still the EC like the other models shows this
wave making slow newrd progress across the state during the day. By
mid to late afternoon...the NAM and GFS indicate steep mid-level
lapse rates and elevated PW over the high country...enough of
support isolated to scattered t-storms by the afternoon. There`s a
slim chance a t-storm or two may also form over the Palmer Divide
after 21z...although with sfc based and bndry layer CAPES less than
500 j/kg...heat driven updrafts than manage to form will be weak and
short-lived. Otherwise the plains should remain dry tomorrow with
max temps ranging from the upper 80s to lower 90s even with an
increase in mid and high clouds through the day. High country should
see high temps reach the upper 60s and 70s before skies cloud over
and t-storms produce rain cooled outflow winds.

.LONG TERM...(Monday night through Sunday)
Issued at 225 PM MDT Sun Aug 21 2016

Colorado and the western half of the country will be under a
broad upper level trough much of the upcoming week and next
weekend. Models in general agreement with this pattern, but the
details need to be worked out, especially during the later
periods.

The first in a series of disturbances embedded in the long wave
trough will start to move across Colorado late Monday. This system
is expected to bring a round of scattered showers and storms,
mainly to the higher terrain. Another disturbance is progged to
move through Tuesday. Models show the best chance for
precipitation will be over the higher terrain. Instability and
moisture will be limited. so expect storms to be on the weak side.
The west-southwest flow aloft will keep temperatures near normal
Monday and Tuesday.

A cold front will push through Tuesday night and bring cooler
temperatures for Wednesday when highs are expected to be in the
70s over northeast Colorado. Airmass should stabilize behind the
front Wednesday, but depending where the next disturbance moves,
showers and storm may be possible. Will keep low pops in for
Wednesday.

For Thursday through Sunday, westerly flow aloft Thursday will
back to the southwest by next weekend as a trough digs south over
the western states. Temperatures will be in the mid 70s to mid 80s
during this period with the warmest temperatures next weekend
under the southwest flow aloft. Models indicate a wave or two
embedded in the flow aloft. Not confident enough to pin point the
timing of these waves, so will broad brush lows pops.

&&

.AVIATION...(For the 18Z TAFS through 18Z Monday afternoon)
Issued at 225 PM MDT Sun Aug 21 2016

VFR conditions in store for the next 24 hours in the Denver
area. Light east-southeast winds this afternoon go drainage/
south-southwesterly with darkness. On Monday...will see a gradual
increase in mid and high clouds throughout the day in advance of
a upper air disturbance moving up from the southwest corner of
the state. Could see a few mostly dry and gusty high based showers
drift northeast over southern and western portions of the Denver
metro area after 22z tomorrow. Could see gusts to around 25 kts
with these showers. Good bet KDEN will miss out on this gusty
shower activity until evening.

&&

.BOU Watches/Warnings/Advisories...
None.
&&

$$

SHORT TERM...Baker
LONG TERM...Meier
AVIATION...Baker



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