Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 220208
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
808 PM MDT Mon Aug 21 2017

.UPDATE...
Issued at 808 PM MDT Mon Aug 21 2017

There are a few weak showers over Park county, otherwise
conditions are dry across the area. Will remove the mention for
showers and storms except for Park county.

Expect easterly winds to continue to advect low level moisture
into the area from Kansas and Nebraska where dew points are in the
60s. Areas of fog should form late tonight and Tuesday morning.

&&

.SHORT TERM...(This evening through Tuesday)
Issued at 340 PM MDT Mon Aug 21 2017

Cooler air is pushing over the plains this afternoon, and will
likely keep that area too stable for convection. Still a low
threat of weak showers/dying storm moving off the foothills for a
few miles. With a little lift we will hold on to low PoPs near the
eastern border. The incoming air near the mountains is dry, but
much richer moisture will move from western Nebraska into Colorado
later tonight. This should produce low clouds and areas of fog
Tuesday morning. Not sure about the threat of dense fog as there
will be some higher clouds and still some wind for mixing, but it
is a possibility.

For Tuesday the cool air mass plus the morning clouds should hold
temperatures back enough that the plains will be capped again
despite the moisture. Main activity should again be on the
interface between the moisture and the warmth over the east slopes
of the mountains, with some possible motion into the adjacent
plains late in the day, with a better chance in the evening.
Forecast highs are near guidance and look good.

.LONG TERM...(Tuesday night through Monday)
Issued at 340 PM MDT Mon Aug 21 2017

The upper ridge axis is over the CWA Tuesday night and Wednesday.
The upper ridge flattens Wednesday night, then weak upper
troughing moves in Thursday night. The synoptic scale energy is
benign Tuesday night through Thursday night. The boundary layer
winds should adhere to normal diurnal trends through the periods.
Precipitable water values are in the 0.50 to 1.30 inches range
Tuesday night. Wednesday through Thursday night values range from
0.50 to 1.10 inches. Surface dew points are in the lower 40s F
west to lower 60s F far eastern plains through the periods. There
is decent CAPE over the mountains and foothills Tuesday evening.
CAPE is pretty good over the mountains again late day Wednesday
and also over the eastern half of the plains. There is CAPE over
all the CWA late day Thursday with the highest amounts over the
eastern plains. The highest pops will be on late day Wednesday and
late day Thursday, pops will be in the 20$-40% for the plains and
30%-60%s for the high country. For temperatures, Wednesday`s
highs are 1-4 C warmer than Tuesday`s highs. Thursday`s highs are
close to Wednesday`s. For the later days, Friday through Monday,
models show the upper ridge building back to the west of Colorado
over the Great Basin. The flow aloft will be westerly Saturday in
the night, then north and northwesterly later Saturday night
through Monday. Moisture is pretty sparse all four days.

&&

.AVIATION...(For the 00Z TAFS through 00Z Tuesday evening)
Issued at 808 PM MDT Mon Aug 21 2017

Mostly clear to partly cloudy skies will prevail through most of
the night. Around 11-12Z low clouds and/or fog may form as moist
air advects into the area from the east. Confidence is high enough
for a tempo for low clouds and half mile visibility. A couple
models do not show this moisture making into the Denver area, so
will not go prevailing yet. There is a chance for quarter mile
visibility with the fog. Best chance for fog will be 11Z to 15Z.
It is expected to lift and clear 15-17Z. Northeast winds will turn
southeast by 06Z and remain east to southeast for much of
Tuesday.

&&

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

$$

UPDATE...Meier
SHORT TERM...Gimmestad
LONG TERM...RJK
AVIATION...Meier


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