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Area forecast discussion 
National Weather Service Denver/Boulder Colorado
410 PM MDT Sat Aug 29 2015

Short term...(this evening through sunday)
issued at 405 PM MDT Sat Aug 29 2015

Smokey skies generally east of the mountains the product of several
active wildfires scattered across the Pacific northwest and
northern Rocky Mountain region. Smoke has thinned though this with
strong heating and mixing. Meanwhile low intensity convection now
underway over the high terrain to the west- southwest of he
Denver metropolitan area. Not seeing any lightning but radar is detecting
a ribbon of light precipitation up along the Continental Divide in park
and Summit counties. At present time...still under a strong/very
warm upper ridge. Ridge axis about to pass over the area as rap
model. Should see light north-northwesterly flow aloft turning southwesterly next
several hours with speeds not much greater. The shift should help
to deflect some of this smoke out of here. Upstream...stronger
southwesterly flow with an 80-90kt jet core over northestern Nevada/northwestern Utah/eastern
Idaho is prognosticated to make its way eastward over the next 24 hours.
Middle/high- level moisture aligned with this jet will spread over
western Colorado tonight and Sunday morning. Model cross sections and
soundings show condensation levels lowering over the high country
through the day with the possibility of scattered showers/T-storms
forming by late morning or early afternoon pretty much from the
Continental Divide westward. By late afternoon should see southwesterly
flow aloft continue to strengthen as the core of moisture aligning
with the continue Divide. East of the mountains...atmosphere should
essentially remain too dry and pretty much capped at mid-levels.
Still...can not rule out a stray storms or two drifting northeast
off the Front Range late in the afternoon. Will go with scattered
probability of precipitation in the high country during the afternoon and only a 10 percent
pop along the base of the foothills late. Otherwise...see little
change in temperature next 24 hours. Lastly...wind speeds and min
relative humidity values are forecast to remain above red flag criteria on Sunday.



Long term...(sunday night through saturday)
issued at 405 PM MDT Sat Aug 29 2015

Area of moisture will drag across Colorado Sunday night into
Monday. There is only slight cooling aloft and the cloud cover
will hold back surface temperatures a little...so instability will
be limited. Current forecast has chance probability of precipitation mountains and slight
chances plains through this period and that looks sufficient.

Drier air aloft will move in Monday night and Tuesday. With more
sunshine this could actually increase convection a bit
Tuesday...though with light southwest flow aloft we may start to
see some drying from mixing along the Front Range. For now will
plan on similar or a bit less coverage...but could have an uptick
in storm intensity.

For the rest of the week we are in light SW flow aloft with dry
air aloft...and we should have a decent dryline near the eastern
border. For the most part expect convection to be capped...but
could have strong convection starting on the dryline if some small
focusing feature appears. Still could have some minor mountain
convection as well but it looks pretty minimal. Decent agreement
on a shortwave passing over the northern rockies about
Saturday...GFS has a weak shallow front while the ec has a bit
stronger impact. Main effect is probably a little cooling Saturday
or Sunday with low level moistening...unsure of the effect on
stability but it looks like most of the forcing will be north of
US. Could set the stage for more activity again Sunday/Monday.

Finally...the smoke. Current batch of smoke coming off the sierras
will be mainly north of US and the southwest flow aloft should
keep most of the higher level smoke going that way. We will of
course be on the edge of it though. However...the low level air we
get behind the fronts might be pretty bad. Expecting another
surge of smoke with the front Monday that might stall over US like
the last two did. I would like to think there would be some mixing
out on Tuesday/Wednesday but there might not be much to dilute it
with light surface winds and some smoke at higher levels from
California. And yes...we will probably be in the same situation
again next weekend as another trough stirs up winds from
California northward Friday/Saturday and then pushes a front into
Colorado over the weekend. Yuck.

&&

Aviation...(for the tafs through 00z Sunday late afternoon)
issued at 405 PM MDT Sat Aug 29 2015

Visibilities have gradually improved through the day as expected
with strong warming and mixing. This trend is expected to continue
with the flow aloft trending more to a west-southwest component.
Meanwhile no chance of storms in the Denver area until perhaps
after 22z Sunday. There is a slight chance one or two weak gusty
storms could drift northeast off of the foothills. May not reach
dia until the evening should this happen. Otherwise dry with VFR
conditions. However lingering smoke in the area may cause ils
Landing approaches at times. Lastly light S-southeasterly surface winds should
remain that way next 24 hours.

&&

Bou watches/warnings/advisories...
none.
&&

$$

Short term...Baker
long term...gimmestad
aviation...Baker

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