Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Denver/Boulder Colorado
304 PM MST Wednesday Dec 11 2013
Short term...winds much lighter across the area due to a decrease
in the northwest flow aloft. Also subsidence and surface pressure
gradient from gjt to den weaker. Still some gusts around 35 miles per hour
over the mountains and foothills. Across far eastern plains...
southwest winds were occasionally gusting to around 25 to 30 miles per hour.
The northwest flow aloft will persist tonight and will continue to
decrease. Still some potential for gust around 30 miles per hour over the
mountains and higher foothills...with winds decreasing across the
far eastern plains as airmass cools. Skies to be mainly clear with
some passing cirrus. With the lighter winds and clear skies...
there should be good radiational cooling though there is less snow
cover across plains. This should allow temperatures to drop into
the teens most areas with single digits in low lying areas near
Greeley and Limon. Temperatures in north and Middle Park expected
to be below zero. On Thursday...the northwest flow aloft becomes a
bit more westerly. The airmass will remain dry with some high
level moisture. 700 mb temperatures warm about 5 degrees celsius.
Thus highs across plains should warm into the middle 40s with
around 50 degrees in the Denver area. Low lying area near Greeley
may struggle to reach 40 degrees. Highs over the mountains to be
in the lower and middle 30s with middle and upper 20s over north
and middle Parks.
Long term...a quiet period in store through the current long
range forecast that ends next Wednesday with temperatures overall
averaging above normal as the mean trough position stays over the
eastern half of the nation. Do not see any chance of precipitation
for the plains. In the mountains right now it looks like the
chance for orographic snow showers Friday into Saturday that is in
the current forecast still looks good although at this point
snowfall amounts look to be light. The system that brings this
snow chance is currently a weakish trough in the eastern Pacific
that moves through the upper level ridge along the West Coast and
then across the area as a shortwave Friday into Saturday. After a
warmer day on the plains on Thursday temperatures drop a bit on
Friday with a surge of northerly flow behind the shortwave.
However right now it looks like things warm up again so that
Sunday through Wednesday could find temperatures into the 50s on
the plains. Always a possibility there could be another northerly
surge and temporary cooling on the plains somewhere in this period
but nothing seen right now in the model forecasts...although
colder air will certainly be lurking off to the east of Colorado.
There could also be some windy periods over higher areas and in
and near the foothills early to middle next week. Model agreement is
good into next week.
The warmer temperatures will likely melt much of the snow cover on
the plains (except in the shade) but looking farther ahead snow
chances increase just beyond this forecast period with a return to
very cold weather also shown. Of course pretty far ahead...but
the deterministic models are in good agreement on a big change to
the pattern and the GFS and naefs ensembles are also rather robust
with this change.
Aviation...weak Denver cyclone just east of dia kept light
northerly winds at kden and kbjc while southerly winds prevailed
at kapa. Models show this cyclone dissipating by 00z with winds
going clockwise to southeast. Will continue this trend for the
upcoming issuance. Drainage flow to then prevail by 05z...speeds
around 8 kts. Weak southerly gradient expected Thursday...should
keep winds southerly...though may briefly shift to the northwest
around 18z. Speeds to be less than 8 kts. VFR to continue with