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Area forecast discussion 
National Weather Service Denver/Boulder Colorado
1156 am MDT Tuesday Sep 1 2015

issued at 1150 am MDT Tuesday Sep 1 2015

Drier airmass today but still some moisture around. Band of deeper
moisture and weak lift has shifted to the southeast fringe of our
area...there should be some weak forcing in this area which will
help Central Mountain/Palmer Divide convection this afternoon.
Across northeastern Colorado it should be pretty well capped.
There is also a little jet streak producing convection in central
Utah at this hour...this will probably move across the northern
mountains in the late afternoon/early evening. Made some minor
adjustments to probability of precipitation and clouds to reflect expected timing of these


Short term...(today through tonight )
issued at 438 am MDT Tuesday Sep 1 2015

Weak west-southwesterly flow aloft is going to continue across
Colorado today with additional sub-tropical moisture. Another
round of showers is going to be possible...especially over the
mountains. Winds aloft will be weak...which could result in slow
storm motions and locally heavy rainfall. The rap and NAM models
keep most of the quantitative precipitation forecast over the mountains...although the NAM
produces some rain out across the Palmer Divide.

Forecast will have the highest chances of precipitation over the
mountains...and isolated coverage across the plains. Temperatures
will be slightly warmer than normal. Turning the calendar to
September has not quite brought an end to Summer yet.

Long term...(wednesday through monday)
issued at 438 am MDT Tuesday Sep 1 2015

The flow aloft will continue southwesterly both Wednesday and Thursday as an upper level
trough resides over the Pacific northwest. Both the European model (ecmwf) and GFS show
some subtropical moisture embedded in the flow which will be over
the area both days. Precipitable water values will be in the 0.5-0.6
inch range over the mountains with values from 0.8-1.0 inches over the
plains. Overall will keep in a slight chance of storms both days across
the area. As for highs readings will remain above normal both days
with low to middle 90s over northestern Colorado.

By Friday little change is expected as an upper level trough remains
over the Pacific northwest with southwesterly flow aloft remaining over the area
with some subtropical moisture still embedded in the flow.
Precipitable water values increase slightly with 0.6-0.7 inches in
the mountains with values at or above an inch across the plains. Thus there may
be some increase in coverage for Friday afternoon into Friday evening. As for
temperatures readings will remain above normal over northestern Colorado with highs in the
upper 80s to lower 90s.

On Sat the upper level trough will begin to shift slowly eastward
with southwesterly flow still over the area. Both the European model (ecmwf) and GFS show
some middle level drying by afternoon especially in the mountains as precipitable
water values drop below 0.50 inches so thunderstorm activity should be
less over the higher terrain. Over northestern Colorado precipitable water
values are still forecast to be at or above an inch. Meanwhile there appears
to be a weak boundary that will be over northestern Colorado in the afternoon which may
act as a focus for thunderstorm development. As for highs 850-700 mb temperatures
drop a few degrees so will keep readings in the 80s over northestern Colorado.

By sun the the upper level trough will move into the northern rockies
with west-southwest flow aloft over the area. Both the European model (ecmwf) and GFS have a
rather dry airmass over the area with a substantial decrease in
precipitable water values. If this is the case then any thunderstorm
activity will be pretty isolated and confined to the plains. As for
highs readings will remain above normal with middle 80s to lower 90s
across northestern Colorado.

On Monday the flow aloft will remain west-southwest as a cool front is supposed to
move across northestern Colorado...however the strength of this fnt is weaker
than what the models showed yesterday. Overall there will be
limited moisture so will only mention low probability of precipitation. Highs will drop
back into the upper 70s to lower 80s over the plains.


Aviation...(for the tafs through 18z Wednesday morning)
issued at 1150 am MDT Tuesday Sep 1 2015

VFR through tonight. Isolated thunderstorms expected in the late
afternoon/early evening...most likely south of Denver. Still a
good chance of a short period of gusty winds to 30 knots...but
only low probabilities of any other impacts.


Bou watches/warnings/advisories...


short term...dankers
long term...rpk

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