Scientific Forecaster Discussion
Area forecast discussion
National Weather Service Denver/Boulder Colorado
329 am MST Thursday Nov 26 2015
Short term...(today and tonight)
issued at 320 am MST Thursday Nov 26 2015
Elongated upper low centered over eastern Nevada and western Utah
early this morning while strong upper jet is oriented northeast
to southwest over western Colorado. The upper low will remain
nearly stationary over the next 24 hours.
There has been an overall enhancement of precipitation during the past 2
hours with the approach of the jet...especially over Larimer and
Boulder counties. This enhancement in radar echoes is resulting in
the freezing drizzle to change to mainly snow across much of
Larimer and Boulder counties. The changeover is also due to
increasing moisture depth and additional cooling in the moist
layer. Further south and east over the Front Range...precipitation type
is still mainly freezing drizzle with a bit of snow mixed in.
Expect this as well should turn to mainly all snow as temperatures
in the column continue to cool and moisture depth becomes a bit
deeper during the morning hours.
Temperatures will be much colder today with readings remaining in
the lower to middle 20s across the plains. Warmer readings in
mountain valleys and west of The Divide...with locations on the
other side of the Arctic airmass. Temperatures tonight will drop
into the lower teens today as additional colder air drops
southward from Wyoming. Looks like some slight enhancement to the
upslope component later this afternoon and evening which will
result in bit better coverage of snowfall this evening. There
will be some diminishment of the snowfall later tonight as the
upper low slowly retrogrades a bit into Nevada.
Overall snowfall amounts today and tonight will be on the light
side due to weak to moderate ascent and low lapse rates. The higher
snowfall amounts will be focused along the Front Range foothills
with enhanced upslope flow of 3-7 inches...2-5 inches over the
urban corridor and 1-3 inches over the northeast plains.
Long term...(friday through wednesday)
issued at 252 am MST Thursday Nov 26 2015
The upper low will continue spinning over the Great Basin Friday
as surface high pressure remains over the Great Plains keeping
upslope flow over the Colorado plains. Light snow will be tapering
off Friday through the day...with a slight resurgence Friday
evening as a piece of energy rounds the low and pushes northeast
over the state. Not expecting much in the way of accumulation as
the main moisture band will be in southern Colorado and further
south. Expect a mostly to all cloudy day with maximum
temperatures in the middle teens to low 20s. The exception will be
Middle Park where temperatures on the west of The Divide may get
near 30. A dry slot should push into the state Friday night for
some clearing in the skies. Low temperatures are expected to cool
down to the single digits to low teens.
The upper low will begin to slowly lift northeast Saturday to Turn
Mountain top flow more southwesterly helping to limit any
precipitation over the plains. Forecast soundings are showing the
airmass dry out over the urban corridor and adjacent
plains...whereas the eastern plains may return to a freezing
drizzle pattern...however not confident to put this in the
forecast just yet. Slightly warmer temperatures are expected
Saturday...but still below freezing.
Models start to diverge on handling the upper low as it continues
to lift northeast across the northern rockies and into the Great
Plains by Tuesday. Overall...look for a chance of snow over the
mountains and far eastern plains. Temperatures should be slowly
warming to above freezing during the day for the plains.
The weather pattern gets messy between the longer range models for
Tuesday and beyond. Have stuck with the general trend of warmer
and drier weather.
Aviation...(for the 12z tafs through 12z Friday morning)
issued at 330 am MST Thursday Nov 26 2015
Arctic airmass well entrenched with IFR conditions in light snow
and freezing drizzle at local terminals. Precipitation type will
continue to change to all snow during the morning. Expect bjc to
turn to all snow earlier in the am with precipitation enhancement to
begin there through 13z. Occasional light snow will continue
through tonight with IFR conditions remaining through the period.
Snowfall accumulations will be around 2-3 inches at dia and apa
and 3-5 inches at bjc by Friday morning. Expect continued
northeast winds at 7-15 miles per hour through the period.
Winter Weather Advisory until 8 am MST Friday for coz035-036-