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Area forecast discussion 
National Weather Service Denver/Boulder Colorado
441 am MDT Wednesday may 6 2015

Short term...(today through tonight )
issued at 441 am MDT Wednesday may 6 2015

Latest radar/satellite imagery shows a well pronounced deformation
zone and area of enhanced rainfall. This rain band extended from
around Cheyenne to Greeley and then to dia and points just east.
The band has pretty much stalled as it just now beginning to show
signs of eastward movement as upper low moves slowly to the
northeast. As the upper trough moves east...this feature will
also continue to rotate slowly east across the plains this
morning. Along the I-25 corridor...a downslope component off the
foothills was allowing some only a slight chance of
showers in and right next to the foothills. Meanwhile...mountain
cams and radar showed snow showers in the high country. Snow level
was averaging 9500-10500 feet. Those showers are expected to
continue this morning with 1-3 inches in the higher mountains of
Summit County as upstream moisture continues to funnel into the
I-70 corridor.

By afternoon...the main batch of showers moving east across the
plains will eventually exit the northeast corner. Meanwhile...a
low level pressure surge from the north and pressure falls to our
south should bring anticyclonic upslope flow to the Front Range.
The airmass will be destabilizing with daytime heating and some
breaks in the clouds. As a result...expect scattered to numerous
showers and a few thunderstorms to develop across the Front Range
I-25 corridor...foothills...and mountains this afternoon where
convective available potential energy should average around 500-800 j/kg.

Showers and isolated storms will gradually decrease by late
evening as airmass gradually stabilizes. A very moist airmass and
light wind field will likely lead to fog formation overnight.

Long term...(thursday through tuesday)
issued at 441 am MDT Wednesday may 6 2015

It looks like another four days of wet weather for north central
and northeast Colorado. Thursday and Friday will see US under weak
southwest flow aloft with the very moist airmass remaining in
place. Model soundings for Thursday afternoon show cape values
around 1000 j/kg. Wind profiles are also expected to become more
favorable for the development of organized convective showers.
This will increase the threat of locally heavy rainfall. Runoff
from showers will be quick...given the soil conditions near
saturation at many locations...including the Palmer Divide...I-25
urban corridor and the foothills of Jefferson and Boulder

On Friday...a surface cold front will be moving into northeast
Colorado as an upper low consolidates over the Desert Southwest.
Easterly low level winds will increase through Friday...helping
strengthen upslope flow at low levels. This will lead to another
round of shower activity by afternoon as the airmass remains quite
moist. Temperatures will be cooler than normal.

Then we come to the the southwestern U.S. Upper low
is forecast to move across Colorado on its way to the northern
plains. During the 24-48 hours that it takes the upper level low
to travel across the state...precipitation will likely be
continuing across much of the forecast area. This system will also
bring cooler temperatures...possibly cold enough to drop snow
levels to the lower Front Range foothills. Some snow may fall
across the plains Saturday night...but it is unclear if there will
be any accumulations at this point. Hydrology concerns will
persist through the weekend. If snow accumulates in the foothills
Saturday and Sunday it could temporarily ease the hydrology
situation...but only until Monday and Tuesday when warmer
temperatures return and melt the Young snowpack. Each of the short
and medium range forecast models depict similar solutions with the
upper low moving across Colorado through the weekend.

Monday and Tuesday have the chance to be drier as the departing
upper level low takes the moist airmass with it and a drier
westerly flow aloft moves over the state.


Aviation...(for the tafs through 12z Thursday morning)
issued at 441 am MDT Wednesday may 6 2015

Lower ceilings under 1000 feet and light rain at kden have been
hanging tough as deformation zone precipitation band held nearly
stationary overnight. Meanwhile...kbjc and kapa have seen some
breaks of the low clouds. The rain band is just beginning to move
east and as long as winds go a little more westerly at kden the
lower ceilings should have a tendency to break up 12z-15z. Patchy
fog may develop where this is partial clearing so will monitor
that through middle morning. Otherwise ceilings will gradually lift
into the 6000-8000 foot range toward 16z-18z. Then scattered
showers and a few thunderstorms will redevelop with daytime
heating and weak frontal push. Enough coverage anticipated for
tempo shower/storm 20z-02z time frame. Then showers and isolated
storms will come to an end 02z-05z. Potential for fog and
visibilities 1/4sm-1/2sm late tonight into Thursday morning.


issued at 441 am MDT Wednesday may 6 2015

Band of precipitation will rotate east across the plains this
morning producing up to another quarter to third of an inch. Some
threat of more significant rainfall this afternoon with convective
development in/near the Front Range foothills. Warm cloud depth is
limited today and storms should be moving 10-15 miles per hour.
However...precipitable water values near 0.70 inch is still near
record levels for this still some threat of localized
flooding issues considering saturated grounds and low flash flood
guidance values. Some streams including Bear Creek and Beaver
Brook are running will continue to monitor those with
any additional rainfall.

Conditions will be little improved on Thursday. Soil moisture
values will remain high and a more unstable airmass will be in
place by afternoon. Thunderstorms that develop Thursday afternoon
will be capable of producing locally heavy rainfall. Areas that
receive rain this afternoon and evening will be in a precarious
situation on Thursday if they receive additional rainfall at that


Bou watches/warnings/advisories...


Short term...barjenbruch
long term...dankers

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