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Area forecast discussion
National Weather Service Denver/Boulder Colorado
924 am MST sun Dec 16 2018

issued at 924 am MST sun Dec 16 2018

A really nice December day is shaping up with light winds, sunny
skies, and mild temperatures. 12z Denver sounding shows a shallow
inversion so full sunshine should be more than capable of pushing
highs well into the 50s across the plains, perhaps touching 60f
in the south/central portions of Denver Metro. Patchy but dense
fog around Granby has been slow to dissipate due to strong
inversions there, and will likely reform tonight with good
radiational cooling.


Short term...(today and tonight)
issued at 335 am MST sun Dec 16 2018

Upper level ridge will be centered over eastern Colorado today.
Subsidence associated with the ridge will result in a very dry
airmass and clear to mostly clear skies through tonight. Surface
high pressure and a weak pressure gradient will lead to light
winds. Mild temperatures are again expected. Due to light winds
and poor mixing, low lying areas may be slow to warm today and may
end up a little cooler. These low lying areas will be chilly
tonight because of the clear skies, light winds, and dry airmass
leading to good radiational cooling.

Long term...(monday through saturday)
issued at 335 am MST sun Dec 16 2018

A few adjustments were necessary to the ongoing forecast out
through day 7. Most notable changes include raising wind speeds a
bit more on the plains Wednesday and nudging Max temperatures up
1-3deg f on Monday and Friday of this week. Otherwise, an
increase in cloud cover is still in order for Monday night and
Tuesday as well as the mention of a few snow showers in the
northern mountains with a passing shortwave trough. Trough still
appears weakly organized and lacking much cold air aloft. Hence
limited instability necessary for a deep cloud layer and favorable
ice Crystal growth. Furthermore, the bulk of the moisture with
this system appears to pass south of the forecast area.

A second batch of moisture associated with a 130+kt jet rounding
the top of a strong upper ridge building off the California coast,
drives southeast over northern Colorado during the day Wednesday.
Qg Omega fields indicate weak ascent, mainly below 500mbs. This
may be an indication of more orographic rather than synoptic
scale forcing. At any rate, most of the precip will likely be
confined to the higher west-northwest facing mountain slopes
Wednesday afternoon. May also see a few light rain showers on the
far northeast plains Wednesday afternoon before the jet passes by.
Once the tail end of the jet passes overhead, subsidence kicks in
leading to a rapid increase in the 850-700 mb northwest flow over
northeast Colorado where winds could gust 45-50 mph Wednesday
afternoon. Drivers of light weight and high profile vehicles
should prepare for strong cross winds should these conditions
materialize. Winds drops off and skies begin clearing Wednesday
evening as the moisture and jet race east of the area.

For Thursday and Friday, dry and warmer weather returns to the
region, but it'll still be breezy at times over and near the
Front Range with Lee slope troughing. The downslope flow produced
by lower pressure on the plains and the warming aloft associated
with a strong upper ridge passing overhead, will produce
temperatures 10-15 deg f above average on Thursday and Friday.
Then, the passage of a weak weather disturbance on Saturday may
return temperatures to near normal and a bring a chance of showers
mainly to the high country.


Aviation...(for the 18z tafs through 18z Monday afternoon)
issued at 924 am MST sun Dec 16 2018

VFR conditions will prevail through tonight under mostly clear
skies. Winds will transition to east/northeast 5-10 knots 18z-
21z and hold til about 00z. Then winds turn back to normal
south/southwest drainage winds through 03z.


Bou watches/warnings/advisories...


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