Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 190244

Area Forecast Discussion
National Weather Service Denver/Boulder CO
844 PM MDT Wed Oct 18 2017

Issued at 845 PM MDT Wed Oct 18 2017

Latest GOES-16 WV imagery shows the dry air slowly sliding south
across our area. The leading edge is currently south of I-70 and
continuing to slide south. This has eroded all but the thinnest of
cirrus, confined to the southern quarter of our forecast area.
Clear skies and very dry air will lead to good radiational cooling
tonight, especially across high mountain valleys and across the
Plains where winds have died down. Tonight`s forecast has this
well in hand and no updates needed.

Only one minor update for tomorrow. With at best thin cirrus, not
expecting mountain wave induced cloud cover in the morning, and
the latest model data show a 1.5 degC warming at 700 mb across our
entire area vs the same time Wednesday....see no reason why highs
Thursday won`t exceed Wednesday`s by a few degrees. We expect a
well mixed boundary layer and similar winds as Wednesday across
the I-25 metro corridor. Have thus bumped up temps 1-3 degrees
most areas for Thursday`s highs. Metro Denver will likely hit 80.


.SHORT TERM...(This evening through Thursday)
Issued at 209 PM MDT Wed Oct 18 2017

A dry conveyor belt pushing south through the evening will
stabilize conditions over the plains and cut off the flow of
moisture from the west. This will dissipate the mountain wave with
a dry cold front bringing increasing NNE winds over the eastern
plains. It will be another mild evening and overnight with lows in
the mid 40s on the plains. For Thursday...upper level flow will
turn more SW with an incoming trough over the Great Basin by
thursday morning. Conditions will be mostly sunny with an upper
level cloud deck and temperatures reaching once again into the mid
70s on the plains. Winds will pick up over the eastern plains
counties mainly east of I-25 by the late afternoon with sustained
speeds of 10 to 15 mph with some gusting to 25 mph at times. RH
values will rebound better than previous days with values in the
20s and 30s over the areas with higher winds. Do not expect
increased fire danger but caution is advised over the windier

.LONG TERM...(Thursday night through Wednesday)
Issued at 257 PM MDT Wed Oct 18 2017

Busy long term period but little in the way of sensible weather.
Upper level flow is characterized by 500 mb trough moving through
the region through the weekend, transitioning to northwest flow
for the remainder of the forecast period. Starting Thursday night
a weak upper trough will pass through Colorado in southwest flow
ahead of the mean trough, however moisture is limited and only a
few clouds will result. South to southwest flow over the region
Friday will continue warm trend, with temperatures on the plains
well into the upper 70s. The main trough moves through Friday
night and although still low moisture will be enough to squeeze
out a little bit of snow in the mountains. Rain at the onset
Friday night, then changing to snow as snow levels lower in colder
air. Vigorous cold front will accompany the upper trough, passing
through after midnight Friday night. Daytime temperatures Saturday
will be noticeably cooler, in the 40s mountains to 50s on the

Sunday through Monday in northwest flow will see a slow moderation
of temperatures and dry weather. A deepening trough will dive into
the central US Monday night into Tuesday with a surface dry cold
front from the north, clipping the far eastern counties with
gusty north to northwest surface winds.

Only changes to model guidance were to beef up surface winds
Thursday night through Monday time frame.


.AVIATION...(For the 00Z TAFS through 00Z Thursday evening)
Issued at 845 PM MDT Wed Oct 18 2017

VFR conditions to continue through at least Thursday. No real
impacts from the wind either. Drainage winds tonight around 10-12
kts at DEN/APA will eventually go south by midday. High res
guidance shows a lee trough just west and southwest of the metro
airports, which will increase the near-surface pressure gradient
from DEN and points east. The southerly flow could reach 15 kts
by mid afternoon at DEN and most likely APA too. The lee trough
elongates to the north along the Front Range west and northwest of
DEN throughout the day, leading to weak winds at BJC pretty much
all day long. Drainage winds should once again occur at all 3
metro area terminals late Thursday evening with relatively weak
pressure gradients across the state after sunset.




LONG TERM...Entrekin/Hanson
AVIATION...Schlatter is the U.S. government's official web portal to all federal, state and local government web resources and services.