Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 122201

Area Forecast Discussion
National Weather Service Denver/Boulder CO
401 PM MDT Tue Sep 12 2017

.SHORT TERM...(This evening through Wednesday)
Issued at 355 PM MDT Tue Sep 12 2017

Upper ridge now centered over wrn Colorado/ern Utah has turned
the flow aloft nwly today. The resident airmass has also dried
considerably with IPW values falling nearly a half inch from 24
hours ago. The few t-storms that managed to form this afternoon
have remained confined to the higher peaks and ridges. As they
drift southeast off the high terrain they quickly glaciate in the
drier air and dissipate over the nearby plains. Still can not
rule out a stray high based storm or two drifting over the
adjacent I-25 urban and perhaps along the Palmer Divide in the
next few hours. But chances are their life expectancies will be
short. Skies should clear in most areas after dark without solar
heating. Lows tonight should be little different from those
observed last night.

On Wednesday...models show the upper ridge shifting east over all
of Colorado, resulting slight warming and further drying aloft.
Therefore storm chances look even lower tomorrow, and mainly
confined to the high country during the mid to late afternoon and
early evening hours. Flow aloft will be lighter and nearly zonal,
and so we could see an isolated brief high based shower or two
drift off the foothills and produce gusty outflow winds and
probably no more than sprinkles or virga for lower elevations.
The sub-cloud environment on the plains will be made drier by a
gentle west-southwest flow downsloping off the foothills. Highs
tomorrow should again be well above average, the same if not
slightly warmer than max temps today. Went with a high of 91 at
Denver. Should the downslope flow become a bit stronger than
expected, could see another few degrees tacked on to that. By the
way, record high for Denver tomorrow is 96. Just saying.

.LONG TERM...(Wednesday night through Tuesday)
Issued at 355 PM MDT Tue Sep 12 2017

Thursday will be one last day of really warm temperatures as the
state remains under southwest flow, ahead of an approaching upper
disturbance. The passing disturbance will be shearing out through
Thursday night, but will still be strong enough to generate
showers, mainly over the mountains. The stronger weather system is
still expected to pass over the state Saturday night. A surface
cold front is forecast to move in Saturday afternoon, with the
upper level dynamics moving over northern Colorado Saturday night.
Although the second system will be stronger than the first, it
will still be deflected northward by persistent upper ridging over
the southeastern United States. A cooler airmass will move in with
the cold front, but moisture will be clearing out before the main
upper dynamics arrive. The higher mountains may see some snow by
Sunday morning, but no accumulation. The upper trough will quickly
move out onto the northern plains by Sunday afternoon as Colorado
come back under warm southwesterly flow. This will bring generally
warmer and drier conditions back to the forecast area.


.AVIATION...(For the 00Z TAFS through 00Z Wednesday evening)
Issued at 355 PM MDT Tue Sep 12 2017

VFR conditions next 24 hours. South-southwest winds of 5-12 kts
overnight becoming west-southwest of 7-13kts by mid to late
morningtomorrow. KBJC and KAPA could see a brief gusty shower or
t-storm late tomorrow.




LONG TERM...Dankers
AVIATION...Baker is the U.S. government's official web portal to all federal, state and local government web resources and services.