573 
fxus65 kbou 022206 
afdbou 


Area forecast discussion 
National Weather Service Denver Colorado 
300 PM MST Tuesday Dec 2 2008 


Short term...main concern is snowfall potential for next 24 hours 
over the County Warning Area. Surface cold front is now across northern portions of Wyoming 
and still expected into northestern Colorado later this evening and over Denver 
around 05z. The moisture is lagging behind the front around 3 hours 
or so...so saturation of the airmass will take a while with shallow 
upslope flow developing. Vertical velocity fields show the best 
ascent is out of sync with the moisture as the best ascent will be 
in the drier air with/ahead of frontal passage. However...feel 
moisture depth coupled with the upslope flow will result in some 
light snow accumlations over the Front Range and adjacent areas. 
Moisture depth becomes more shallow by afternoon so only isolated probability of precipitation 
expected over the plains. Much colder temperatures as soundings only 
supporting highs in the lower 30s. 


Across the mountains...moisture will increase rapidly this evening and 
then Shallows out a bit during the day on Wednesday. With the 
orgraphic northwest flow of 10-20kt and decent lapse rates...mountains 
should be able to keep some light accumlations on Wednesday as well. 
No hilites appear needed at this time. 


Long term...colder and unsettled weather will hold over the 
forecast area through Thursday night as a cold dome of high pressure 
builds slowly southward across the High Plains. In addition... 
embedded disturbances and a jet maximum will drop across the region 
aiding the chance of snow. 


For Wednesday evening...the subsidence behind tonights short wave 
will be replaced by middle level frontogenetical forcing and lift as 
seen in the q-g fields. An upper level jet will also skirt across 
the northeast corner of the state later in the night...leaving the 
forecast area in the favored right entrance region of the upper 
jet. Meanwhile...the cold and moist airmass will remain locked 
across the plains keeping weak upslope flow in place. This will all 
help snow development...with the northern border area looking to be 
in the best shape at this time given the expected location of the 
upper level features and deeper moisture. In addition...cross 
sections show potential release of conditional symmetric instability 
so cant rule out a few heavier bands of snow. Orographics are 
rather weak in the mountains and mainly westerly...so this should 
keep snow accumulations on the light to moderate side with the 
heaviest snow north of I-70. 


On Thursday...the whole pattern should shift southward as the jet 
and frontogenetical area sag across eastern Colorado. This will 
spread the better chance of snow to the southern portions of the 
forecast area as well. Again...cant rule out some banded snow and 
with models coming into better agreement with this scenario will 
increase the chance of snow considerably through Thursday. 


Snow will be tapering off from north to south Thursday night as 
subsidence takes over again. Friday through Sunday will then 
feature mainly dry weather with a warming trend. Next system still 
on track according to the various medium range models and their 
ensembles to reach the area Monday so will introduce a chance of 
snow in the lower elevations then. 


$$ 


Aviation...surface winds appear to be settling into a west-northwest direction 
and maybe a few gusts to around 20kt until 01z. Surface cold front 
will move across local airports between 04-06z with low level moisture 
lagging behind the front. -Sn will develop in the 08-10z time frame 
with IFR/MVFR ceilings/visibilities developing. 


&& 


Bou watches/warnings/advisories...none. 




$$ 


Entrekin/barjenbruch