Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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806
FXUS65 KBOU 190929
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
329 AM MDT Tue Sep 19 2017

.SHORT TERM...(Today and tonight)
Issued at 209 AM MDT Tue Sep 19 2017

An upper level trough will move across the nrn Rockies this aftn and
evening with brisk WSW flow aloft over nrn CO.  There will be some
mid lvl ascent, which will combine with just enough moisture to
produce a chc of showers in the mtns mainly nr the WY border late
this aftn and evening. Otherwise the rest of the area will be dry
with gusty winds thru the aftn hours. As for temps, with downslope
WSW low lvl flow, this should allow for aftn highs to reach the
mid 80s to lower 90s over nern CO.

For tonight the shower threat in the nrn mtns should end by
midnight.  Meanwhile a pacific fnt will move across the plains
during the early evening hours with a brief period of gusty NWLY
winds behind it which will bring cooler temperatures.


.LONG TERM...(Wednesday through Monday)
Issued at 335 AM MDT Tue Sep 19 2017

West-southwesterly flow aloft is progged on Wednesday.  The flow
aloft becomes southwesterly Wednesday night trough Thursday night.
As an upper trough/closed low gets into the Great Basin by 12Z
Friday morning, the southwesterly flow aloft over Colorado
increases in speed. The synoptic scale energy is benign Wednesday
trough Thursday, but weak upward motion gets over the CWA Thursday
night on the QG Omega fields. For the boundary layer winds, there
is southeasterlies progged on Wednesday, normal drainage patterns
Wednesday night, downsloping southwesterlies on Thursday and more
drainage Thursday night. There is little moisture around through
the periods. Precipitable water values are in the 0.25 to 0.50
inch range for the CWA Wednesday through Thursday night. There is
no measurable rainfall on the QPF fields Wednesday through
Thursday night. No pops. For temperatures, Wednesday`s highs are
1-4 C cooler than Tuesday. Thursday`s readings are 1-5 C warmer
than Wednesday`s. Concerning the days Friday through Monday,
increasing southwesterly aloft is progged on Friday. A fairly
strong cold front moves in Friday night. There is a jet maximum
over the CWA on Saturday with southwesterly flow aloft. South-
southwesterly flow aloft is progged Sunday. On Monday the ECMWF
starts getting the trough into the forecast area. The GFS still
has southwesterly flow aloft with the trough axis still to our
west. Moisture increases significantly later Friday through next
Monday. There is some QPF as well. Temperatures cool off to below
seasonal normals Saturday through Monday.

&&

.AVIATION...(For the 06Z TAFS through 06Z Tuesday night)
Issued at 209 AM MDT Tue Sep 19 2017

VFR conditions today thru tonight. Winds will be SSW early this
morning however am not very confident about directions lats this
morning into the early aftn hours. Both the HRRR and RAP indicate
a weak sfc low will develop near or SW of DIA by late morning
which would keep winds more s or se thru 20z. By 21z both show
winds becoming WSW as mixing occurs with some gusts up to 25 mph
thru 01z. By 04z or 05z a cool fnt will move across with winds
becoming NLY for a few hours. Overnight expect winds will
gradually shift to drainage by 09z.

&&

.FIRE WEATHER...
Issued at 335 AM MDT Tue Sep 19 2017

Critical to Extreme Fire Danger will exist this aftn into the
early evening hours across most of the area due to low humidity
and gusty winds. Fire danger will decrease after 8 pm as winds
gradually decrease and humidity levels recover behind a cool
front. Wednesday is expected to be a cooler and a little less
windy but there will still be elevated fire danger. Temperatures
increase again Thursday, but the winds are not very strong. There
will still be elevated fire danger.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
Red Flag Warning from 11 AM this morning to 8 PM MDT this
evening for COZ212>216-238>251.

&&

$$

SHORT TERM...RPK
LONG TERM...RJK
AVIATION...RPK
FIRE WEATHER...RPK/RJK



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