Area Forecast Discussion
Issued by NWS Denver/Boulder, CO

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FXUS65 KBOU 010249
AFDBOU

Area Forecast Discussion
National Weather Service Denver/Boulder CO
849 PM MDT Fri Sep 30 2016

.UPDATE...
Issued at 841 PM MDT Fri Sep 30 2016

Showers will come to an end over the next few hours in
Park...Elbert and Douglas counties with mostly cloudy skies over
the mountains moving to partly cloudy on the plains. Temperatures
will be cooler then last night due to less nocturnal cloud cover.
Made adjustments to pops and weather to be more
representative...otherwise forecast is on track.

&&

.SHORT TERM...(This evening through Saturday)
Issued at 645 PM MDT Fri Sep 30 2016

Today and tomorrow a weak upper trough will be slowly moving east
through the weak upper ridge over Colorado. The airmass over
Colorado is quite moist (GJT was over 200 percent of average this
morning) and there were numerous cloud levels over the mountains.
There is some clearing seen in the higher clouds over Colorado...
and we just now seeing lightning over the western mountains. At
the surface a low pressure center resides over southeast
Colorado...and an apparent front went through metro Denver this
morning and is seen moving through the Pueblo radar at 20z. The
boundary and the clouds resulted in slightly cooler temperatures
today.

New HRRR continues the idea of precipitation shifting to the
southeast this evening. That is reflected in the forecast so no
changes...scattered pops over the Palmer Divide this evening...then
showers diminishing across the CWA by midnight.

Saturday will be similar...as the moisture will continue to reside
over the mountains and the southwest flow will continue. There will
be scattered showers and thunderstorms over mountains...with a much
lower chance over the plains. Temperatures will be only a degree or
two higher than today.

.LONG TERM...(Saturday night through Friday)
Issued at 645 PM MDT Fri Sep 30 2016

Saturday night the upper level trough will be centered over the
Rocky Mountain Region...with a deep upper level low pressure
trough just off the west coast of the United States. On
Sunday...the upper ridge will shift eastward over the Central
Plains as the upper level storm system deepens over northern
California. This pattern should result in dry and warm weather
across north central and northeastern Colorado through the
weekend...with only isolated showers and storms in the mountains.
On Monday...the upper trough deepens over the Great Basin...with a
moderate to strong southwesterly flow aloft over Colorado. Models
are showing a 100kt+ KT jet over western Colorado by Monday
Afternoon. Some orographic and lift from the upper jet should
produce scattered afternoon and evening showers and storms over
the high country...with dry and warm weather east of the
mountains.

On Tuesday...the center of the upper low tracks north of Colorado.
The GFS has it moving over Wyoming and the Dakotas...while the ECMWF
moves it over Montana. The combination of the frontal passage and
cold air advection from the upper trough will bring an end to the
unseasonably warm temperature across the region. Temperatures on
Tuesday should be 15 to 20 degrees colder than Monday`s readings.
Cold advection behind the front...combined with the gradient between
the upper high over the northern Rockies and higher pressure over
Colorado should produce gusty winds over the foothills and portions
of northeastern Colorado from early Tuesday morning through Tuesday
afternoon. The Sangster Model suggests the potential for strong
winds across the foothills. In addition...the northern mountains
should see a good chance for snow due to cold air advection and
orographic westerly flow.

Wednesday should be the coolest day of the week on the plains due to
increasing cloudiness and less downslope flow. We should still see
scattered snow showers in the mountains due to a continued westerly
orographic flow. The models also show an upper level disturbance
moving across the region...which could produce isolated showers
across the plains.

Warmer and drier weather is expected by Friday as upper level high
pressure rebuilds over the Rocky Mountain Region.

&&

.AVIATION...(For the 00Z TAFS through 00Z Saturday evening)
Issued at 841 PM MDT Fri Sep 30 2016

VFR conditions are expected for the next 24 hours. Winds will
move to drainage by 3z and stay from the SW through the period
with light speeds. Ceilings will remain until around 4z with a SCT
deck through tomorrow afternoon until another round of moisture
will bring an upper level BKN deck with thunderstorms possible in
the vicinity. I am not confident that DIA will see convection on
station but there is still a 10-20% chance of some development by
the late afternoon.

&&

.BOU WATCHES/WARNINGS/ADVISORIES...
None.
&&

$$

UPDATE...Bowen
SHORT TERM...RTG
LONG TERM...Kalina
AVIATION...Bowen



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