Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 132017
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
217 PM MDT Thu Aug 13 2020

.SHORT TERM...(This evening through Friday)
Issued at 140 PM MDT Thu Aug 13 2020

Another hot afternoon across the plains with temperatures already
in the lower 90s across most locales. Just some cumulus clouds so
far this afternoon as airmass has already well mixed over the
Front Range. Across the far northeast plains, dewpoints in the
40s/50s but expect falling dewpoints there as well during the next
few hours with further mixing. Still an ever so slight chance for
a storm where the moisture is still holding, generally across
Logan, Phillips and Sedgwick counties. Elsewhere dry conditons
through tonight.

Main concern is the amount of haze and smoke expected over the
region through Friday from the Pine Gulch and Grizzle Creek Fires.
The westerly mid level flow will continue to influence the airmass
as the smoke from the fires comes right across the Interstate 70
corridor and into the Front Range and northeast plains. Latest HRRR
smoke forecast increases the smoke again towards 00z over Denver and
spreads over the plains through midnight and continues through
Friday morning.  Will be adding more haze and smoke to the forecast
to account for this.

Later tonight and Friday morning an upper trof will traverse the
northern high plains which will increase the mid level flow (35kt)
and bring down an associated cold front across the plains during the
morning hours. Unfortunately there is not really any cold air with
it and no moisture to speak of along with a slightly subsident airmass.
Temperatures will again be well into the 90s while precipitable water
values remain around a third of an inch over the Front Range. The
only good news is that the flow aloft will begin to shift northwest
later in the day, so less smoke likely especially over northern
sections of Colorado by afternoon.

.LONG TERM...(Friday night through Thursday)
Issued at 140 PM MDT Thu Aug 13 2020

The upper level ridge axis builds across the western U.S. Friday
night and Saturday. The ridge amplifies and shifts eastward Saturday
and remains in place through midweek. Models show a disturbance
moving over the top of the ridge and flattening it a bit toward the
end of the extended period.

At the surface, low level upslope flow continues through the first
part of the weekend. The dry and warm airmass limits chances for
precipitation. Only widely scattered thunderstorms are possible
Saturday afternoon on the far eastern plains. On Sunday, another
frontal boundary moves south through the eastern plains. Could see a
few more thunderstorms develop farther west with deeper upslope flow
and slightly better moisture. Still kept pops to be in the 20-30
range.

Once the ridge axis shifts farther east, expect north to northwest
flow aloft across the area. Expect some thunderstorms to develop
each day with moisture trapped underneath the high and weak
disturbances moving through the flow.

Highs on the plains will be in the mid 80s to mid 90s Saturday and
Sunday. Highs drop back a few degrees for Monday through Thursday
with a bit more cloud cover. Stark

&&

.AVIATION...(For the 18Z TAFS through 18Z Friday afternoon)
Issued at 140 PM MDT Thu Aug 13 2020

VFR conditons will continue however with smoke/haze
expected to increase again tonight expect there will be varying
ILS approach conditions across local terminals. Otherwise very dry
conditions with no showers/storms expected through Friday.
Generally variable surface winds this afternoon which will shift
east and southeast this evening and then the usual southerly winds
later this evening and overnight.

&&

.FIRE WEATHER...
Issued at 140 PM MDT Thu Aug 13 2020

Slight recovery for humidity levels tonight while winds relaxing
this evening. Mountain top flow does increase later tonight and
Friday morning and could see gusts up to 30kt Friday morning. Flow
decreases Friday afternoon so won`t coincide with lowest humidity
levels in the afternoon. There will still be elevated fire danger
with the low humidities but expect winds under 20 mph with the
lowest humidities during the driest parts of the afternoon. Hence
no red flag warnings will be issued at this time. Fire danger will
remain elevated through Saturday, but winds will generally be
light. On Sunday, moisture increases on the eastern plains with
generally light winds. It will continue to be very warm and mostly
dry through the middle of next week with a slight chance of
thunderstorms Monday through Thursday.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning until 8 PM MDT this evening for COZ211-213-217-
218.

&&

$$

SHORT TERM...Entrekin
LONG TERM...Stark
AVIATION...Entrekin
FIRE WEATHER...Entrekin



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