FXUS65 KBOU 222158

Area Forecast Discussion
National Weather Service Denver/Boulder CO
358 PM MDT Sat Sep 22 2018

.SHORT TERM...(This evening through Sunday)
Issued at 309 PM MDT Sat Sep 22 2018

It's another very warm dry September day, with dew points
dropping a bit lower than previously expected as the driest air is
over us now. There will be a bit more moisture around 700 mb by
Sunday afternoon, which will likely result in a little cumulus
development, but this layer is fairly shallow with very dry air
above it around 500 mb. With slight warming and full sunshine, we
should be close to the record of 90 degrees on Sunday. Little
change needed to the forecast, but we did increase the winds over
the higher terrain a little, and lower dew points a little in line
with the latest guidance. See the fire weather section below for
more on that.

.LONG TERM...(Sunday night through Saturday)
Issued at 309 PM MDT Sat Sep 22 2018

A shortwave will pass through Wyoming and northern Colorado
Sunday night and into Monday while a cold front will sweep through
the eastern plains Monday morning. This will provide enough lift
to create a few showers but the best ascent will be north of the
CWA so precip amounts will be very light. Behind the cold front,
winds over the plains will shift to an easterly, upslope flow with
more moisture in the low levels. With large lapse rates of around
8 degrees per kilometer from the surface through 500 mb, a few
thunderstorms will develop during the afternoon. POPs were
increased Monday afternoon to account for the storms.

A secondary and stronger cold front will push through the eastern
plains Tuesday morning decreasing high temperatures to the mid 60s
in Denver. This will finally break the streak of 17 consecutive
days of above normal temperatures in Denver assuming the above
normal temps verify Sunday and Monday. This front, along with a
shortwave trough moving southeastward through Colorado from the
Pacific Northwest, will provide the ascent for a chance of showers
from tuesday morning into Wednesday morning.

Forecast uncertainty increases a bit beyond Wednesday as models
are struggling to predict a Rex block a few hundred miles off the
west coast of the U.S. Models currently break this pattern down
late Friday and into Saturday allowing a ridge to build over the
southwest U.S. If this were to verify, temperatures across much of
Colorado would be well above average with elevated fire weather


.AVIATION...(For the 00Z TAFS through 00Z Sunday evening)
Issued at 309 PM MDT Sat Sep 22 2018

VFR through Sunday. There will be some wildfire smoke, mainly
aloft and mainly north of Denver. It will likely not be thick
enough to impact Denver area airport operations.


Issued at 309 PM MDT Sat Sep 22 2018

We are near Red Flag warning criteria in the northern mountains
now, with low humidities and marginal winds. On Sunday we will
have stronger winds, but humidities will be higher and generally
at or above the 15% criteria. Valley locations like Kremmling and
Walden should meet the criteria for a few hours in the afternoon,
while higher areas will have stronger winds but higher humidities.
We've opted not to issue a warning for this marginal situation,
but it will certainly be another day conducive to active burning.




SHORT TERM...Gimmestad
LONG TERM...Danielson
FIRE WEATHER...Danielson/Gimmestad
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