Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Denver/Boulder Colorado
905 PM MDT Thursday Sep 18 2014

issued at 905 PM MDT Thursday Sep 18 2014

No updates to the forecast are necessary this time around. Clear
skies across the forecast area should continue most of the night.
Southerly winds coming off the Palmer Divide should help keep
temperatures mild for a few more hours. By sunrise...lower winds
will allow temperatures to cool off to the lows that we have in
the current forecast.


Short term...(this evening through friday)
issued at 204 PM MDT Thursday Sep 18 2014

The airmass will be dry and stable overnight as a ridge of high
pressure continues over Colorado. The ridge axis will shift east
by Friday morning with as a weak upper level disturbance passes to
the north. A cold front will move into the Denver area by 18z with
weak northeasterly winds in the afternoon. Thunderstorms will make their return
in the mountains and foothills...possibly slipping into the urban
corridor by late afternoon.

Long term...(friday night through thursday)
issued at 204 PM MDT Thursday Sep 18 2014

Upper level ridge axis will extend from New Mexico across western
Colorado and northwestward to the Pacific northwest Friday night and
Saturday. This will produce a weak northwest flow aloft. At the
surface...a cold front will push south across the state Friday
night. There will be some moist and weak instability ahead of the
front Friday will continue with the slight chance for
showers and thunderstorms. The cold front will bring cooler
temperatures for Saturday...though temperatures are expected to
remain near normal...upper 70s for northeast Colorado. Still some
question if we will see low clouds early Saturday. Right now it
looks too dry...but if low clouds form would expect them to keep
high temperatures slightly lower. May see some afternoon and evening
convection Saturday. The plains may be capped by the cooler airmass
so chances will be low. The better chance will be over the elevated
terrain...including the Palmer Divide.

The upper level ridge axis shifts over eastern Colorado by Sunday as
an upper level low moves across Nevada. Southwest flow aloft is
expected to transport moisture into the area. The increase in cloud
cover and moisture will lead to slightly cooler temperatures.
Precipitable water values will climb to an inch or slightly higher
Sunday afternoon...more than two Standard deviations above normal.
Convective available potential energy will be up to 1000 j/kg. So expect scattered thunderstorms
Sunday afternoon and evening with a few possibly producing heavy

For Monday and Tuesday...the upper level low will move from Nevada
into Wyoming Monday and into the northern plains Tuesday. A short
wave or two may rotate around the low and across Colorado. Airmass
will dry slightly each day...but remain moisture for this time of
year. Expect a round of scattered convection both Monday and
Tuesday. Temperatures will remain near normal.

On Wednesday...a dry northwest flow aloft will prevail over Colorado
as a ridge builds over the Great Basin. This ridge will shift east
Thursday keeping conditions dry. Temperatures will be near to
slightly above normal under this pattern


Aviation...(for the tafs through 06z Friday evening)
issued at 905 PM MDT Thursday Sep 18 2014

Will extend the gusty southerly winds for a few more hours since
radar data is showing a boundary coming off the Palmer Divide.
Kmnh is showing gusts up to 25 knots...indicative of the winds we
might see at kapa and kden over the next few hours. After that the
winds should return to more typical drainage speeds.


Bou watches/warnings/advisories...


short term...Cooper
long term...meier

National Weather Service Glossary of Abbreviations