National Weather Service Forecast Discussion

000
FXUS65 KBOU 102135
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
335 PM MDT Mon Aug 10 2020

.SHORT TERM...(This evening through Tuesday)
Issued at 201 PM MDT Mon Aug 10 2020

After a slightly cooler day today the heat returns on Tuesday as
the 500mb ridge axis is centered over Colorado tonight and
tomorrow. For the rest of the evening a few isolated showers are
possible that survive the trek east off the foothills. Little if
any rain should reach the ground, but gusty winds to 40-50 mph are
possible near any active/decaying storms. Tonight should be
mostly clear with seasonal overnight lows.

HRRR-Smoke is helping track the evolution and concentration of
smoke from the Pine Gulch fire north of Grand Junction. Expect a
very hazy morning across Grand and Summit Counties, bleeding over
the Divide into Boulder, Clear Creek, Gilpin, and Jefferson
Counties (maybe northern Park too) by sunrise. Surface vis should
be okay, but it`ll look awfully hazy relative to the normally
stellar visibility we enjoy most of the time in Colorado. The
smoke/haze shouldn`t slow the warming expected on Tuesday, with
700 mb temps rising to +17 degC across our area and a bit of
downslope east of the Divide expected. Temps should reach the mid
90s across the plains and urban corridor, and remain hot in the
mountains with 80s in the valleys and even 60s around timberline.

In terms of convection on Tuesday, the atmosphere is flat out dry
across most of the area. PW values will range from 0.25" over the
high country to 0.5" across I-25 corridor and east. Only the far
eastern plains will be around 1.0". Weak, isolated afternoon
convection should occur across the mountains and Palmer Divide,
but not much rain is expected across the I-25 corridor east to
about an Akron to Strasburg line. Briefly gusty winds are
expected during the evening hours associated with any convection.
There should be a convergence zone that sets up somewhere across
eastern Washington/Logan Counties south into eastern Lincoln
County. East of this quasi-dry line CAPE values could exceed 2500
J/kg, supporting marginally severe storms after 2 or 3 PM. Deep
layer shear is lacking so if there is severe convection it will be
of the pulse storm (up/down/splat) variety with microbursts and
marginally severe hail possible.

.LONG TERM...(Tuesday night through Monday)
Issued at 320 PM MDT Mon Aug 10 2020

A mid to upper level ridge will develop and strengthen over the
Desert Southwest by mid week and will last all the way through at
least the middle of next week. This will keep conditions hot and
dry for our CWA much to the dismay of those hoping for a break in
the summer heat.

There seems to be a lack of substantial shortwave troughs at any
point during the long term period to generate a good chance of
precipitation across the area. At the surface, weak cold fronts
will pass through our forecast area Friday and Sunday. The Friday
cold front will not affect temperatures and dew points very much
but the Sunday cold front may have the potential to decrease
temperatures closer to normal and increase moisture.

Each afternoon and evening may have just enough instability to
create a couple showers and storms mainly over the mountains and
far eastern plains. With inverted-V soundings extending up to 500
mb most days, these showers and storms will likely produce more
wind than rain. Coverage of these showers and storms will be
minimal so PoPs were kept rather low throughout the period.

Fire weather may be a slight concern due to the very low relative
humidities that will reach the single digits across the plains and
mountain valleys each day. Winds will generally be light enough to
keep fire danger on the lower side. An exception may be on Thursday
in North park as winds may gust up to 25 mph during the
afternoon.

&&

.AVIATION...(For the 18Z TAFS through 18Z Tuesday afternoon)
Issued at 201 PM MDT Mon Aug 10 2020

VFR conditions through Tuesday. Gusty outflow winds are still a
possibility early this evening with weak convection that is trying
to get going across the higher terrain to the west. Gusts around
30 kt are possible but still too uncertain on direction and
timing to include in the TAFs. Southeast winds around 10-15 kt
will go SW at APA and DEN after midnight, W at BJC. On Tuesday it
will be very hot and dry at the terminals, again with an isolated
chance of a convectively-driven wind shift late afternoon/early
evening. Winds should be W to WSW throughout the day until/if a
gust front occurs.

&&

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

$$

SHORT TERM...Schlatter
LONG TERM...Danielson
AVIATION...Schlatter

NWS BOU Office Area Forecast Discussion