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Area forecast discussion 
National Weather Service Denver Colorado 
242 am MST Monday Nov 23 2009 


Short term...an upper level trough will move across the area through 
midday with some decent qg ascent in the middle levels. This system is 
already producing snow in the mountains and will continue to do so 
through the late morning hours. Main headache for today is over 
northestern Colorado. A cold front will move across northestern Colorado later this morning 
with north-northwest low level flow. As this fnt moves across and combines with 
passage upper level trough and qg ascent could see a brief period of 
enhanced snow shower activity over the plains which could drop a 
quick inch of snow in a few spots from middle morning through the early 
afternoon hours. Latest RUC keeps most of this precipitation east if the I-25 
urban corridor however if low level winds briefly become more north-northeast 
for an hour or two that could lead to some snow from Denver south to 
the Palmer Divide. Thus will mention chance probability of precipitation for through 18z for all 
of northestern Colorado and mention some minor accumulations. By this afternoon the 
system is forecast to move rapidly southeast and intensify over southwestern NE/northwestern 
Kansas. Thus could see some lingering snow over the far northestern corner 
through late afternoon with drying conditions along the Front Range as northwesterly 
downslope low level flow occurs. In the mountains moisture is forecast to 
linger through the afternoon hours and with northwesterly flow in place may still see 
some light orographic snows. Temperatures will be quite a bit 
colder behind the front with highs mainly in the upper 30s to lower 
40s across northestern Colorado. 


For tonight the upper level trough will move away from the area with 
drier air spreading across the entire area. However could still see 
a few lingering -shsn in the mountains and over the far northestern corner early 
this evening before precipitation ends. 




Long term...weak ridging aloft will move over Colorado on Tuesday 
with dry and warmer conditions. The next disturbance will dive into 
the Central Plains on Wednesday and brush the far northeast plains 
of Colorado. The GFS presents a bit more moisture and even some light 
quantitative precipitation forecast over the far plains where the NAM is drier. Will add a 10 pop 
over the far northestern Colorado zones from late Tuesday night and Wednesday am. 
Broad...large scale ridging builds across the state on Thursday and 
Friday with dry conditions and warming temperatures. For the weekend time 
period...the next upper level disturbance moves across Colorado but 
there is still a lot of uncertainty within the long range models. 
The European model digs more energy into the desert soutwest while 
the GFS still showing a wide variety of solutions amongst its 
ensemble members. Despite the uncertainty will add at least a slight 
chance for the mountains and cooler temperatures for entire County Warning Area. 


&& 


Aviation...tricky forecast for the middle morning hours as passage of cold 
front and upper level trough could produce a 1-2 hour window of 
steadier snow between 14z-16z which could briefly produce up to an 
inch of snow along with low ceilings and visibilities if precipitation does 
develop. This system will move across rather quickly so conditions 
should improve by 17z I would think. Winds with the front will be 
out of the north-northwest in the 15-20 miles per hour range with a few gusts to 25 miles per hour 
possible. By early this evening winds will quickly diminish with 
winds becoming drainage after 03z. 






&& 


Bou watches/warnings/advisories...none. 


$$ 


Rpk/swe