780 
fxus65 kbou 202136 
afdbou 


Area forecast discussion 
National Weather Service Denver Colorado 
235 PM MST Friday Nov 20 2009 


Short term...upper level ridge over Colorado will shift eastward 
tonight and Saturday. Meanwhile...next short wave now moving onto 
the West Coast will begin to approach the forecast area by Saturday 
afternoon. As a result...southwest flow aloft will be increasing 
tonight through Saturday morning. This should result in a mild 
night across the Front Range with better downslope component 
overnight. Temperatures tomorrow will warm again to above normal 
levels...but increasing high clouds and weak cold advection should 
keep readings slightly below todays highs. Enough cold and moisture 
advection noted late in the day to keep a chance of snow around 
Rabbit Ears Pass for the late afternoon hours...but chances for the 
Front Range mountains should hold off until Saturday evening. 


Long term...the first upper trough will be moving across the state 
Saturday evening through early Sunday morning while pushing a cold 
front south over the region. With little moisture contained in this 
system...only scattered snow showers are expected over the northern 
high country. Maximum temperatures will be lowering about 10 degrees on 
Sunday as a second even stronger system races out of the Pacific 
northwest on the nose of a +140kt Pacific jet. Models are still 
diverging on this system with regard to the timing and strength of 
this system. It seems as the GFS solution is too fast and more 
confidence is being placed on the European model (ecmwf) solution which pulls the low 
a little farther south. Have trended forecast more toward this which 
will bring a better chance of precipitation to the plains. Winds 
over the high country and foothills will be increasing Sunday ahead 
of this system. Expect snow to begin over the mountains Sunday early 
afternoon. A chance of rain mixing with snow will spread onto the 
plains in the evening with the best chance of snow occurring on 
Monday. If the European model (ecmwf) solution is correct...could see very gusty 
northerly winds over the plains and westerly winds through the high 
country and foothills as the surface low deepens over Kansas. For 
now have kept winds below 25 miles per hour over the plains with wind gusts 
possibly reaching 60 miles per hour through the foothills. Will have to keep 
revisiting the model solutions for better confidence. A third 
shortwave could brush northeastern Colorado Tuesday night into 
Wednesday...however the ec is now pushing this further east. 
Again...will have to keep reviewing the solutions run to run. All 
models are pointing to an upper ridge building in over the state 
Wednesday night through Thursday night...bringing warmer and dry 
weather for the Thanksgiving Holiday. 


&& 


Aviation...visual Landing conditions will prevail through Saturday 
with only high clouds above 20 thousand feet. Typical diurnal wind 
patterns and speeds will prevail. 


&& 


Bou watches/warnings/advisories...none. 


$$ 


Barjenbruch/kriederman