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fxus65 kbou 212143 
afdbou 


Area forecast discussion 
National Weather Service Denver Colorado 
243 PM MST Sat Nov 21 2009 


Short term...latest RUC qg analyses indicate strengthening ascent 
ahead of short wave trough presently over Utah. Clouds are also 
thickening in response to this lift. All of the models are similar 
with this feature...dragging it across the County Warning Area by 18z Sunday. They 
also all bring some quantitative precipitation forecast in one form or another east of the hills 
overnight although the excessive amounts predicted by the 12z NAM 
around Denver seem out to lunch. Will bump plains probability of precipitation up just a 
little bit to account for this. The subsidence behind tonight/S 
wave is rather short-lived in the western sections with ascent from 
the next system gradually encroaching into those locales of the County Warning Area 
after 18z. This may be sufficient to lift a bit of moisture in zone 
31 to create some light snow shower activity there later in the 
afternoon. Warmer temperatures tonight due to cloud cover and 
cooler tomorrow as cold air drags itself over the state. 


Long term...next upper level trough is on track to push rapidly 
eastward across Wyoming Sunday night and then close off somewhere 
over Nebraska by Monday. The medium range models have come into 
fair agreement with this system...so the main weather story with 
this feature should be a period of snow and 1-4 inches in the 
mountains Sunday night into Monday...and then gusty northwest winds 
but only a slight chance of snow showers across the plains. There 
is still a risk that the storm could dig a bit more than indicated 
due to the amount of energy still seen out in the Pacific...so will 
keep the chance of snow wording across the northeast corner. 
Temperatures will be considerably colder on Monday with strong cold 
advection supporting highs closer to 40f...and gusty northwest winds 
making it feel even colder. Forecast soundings show potential for 
40 knot gusts across the northeast plains of Colorado as storm 
system winds up over the Central Plains states. 


By Tuesday...winds will be gradually decreasing as flow slowly 
relaxes across the forecast area. There may be another weak frontal 
surge Tuesday night into Wednesday to keep cooler readings in place 
through then...with temperatures generally a couple degrees below 
normal. This front appears weak enough to keep a dry forecast in 
place. By Thanksgiving...there is good agreement that an upper 
level ridge will build over the central rockies. This will bring a 
return to above normal temperatures which should continue into 
Friday. By next weekend...there are some indications by the medium 
range ensembles that a cold front will drop southward across the 
plains with a return to cooler temperatures then. 


&& 


Aviation...there is a small threat of some snow shower activity 
tonight from around 06z to around 13z. Little accumulation is 
expected from any showers that make it off the mountains however 
ceilings and visibilities may be impacted to disallow visual 
approaches for a bit later tonight and early Sunday. Winds should 
remain rather light. 


&& 


Bou watches/warnings/advisories...none. 


$$ 


Et/barjenbruch