799 
fxus65 kgjt 202111 
afdgjt 


Area forecast discussion 
National Weather Service Grand Junction Colorado 
211 PM MST Friday Nov 20 2009 


Short term...tonight through Sunday night... 
current water vapor imagery highlighting positively tilted ridge of 
high pressure directly overhead County Warning Area this afternoon as middle-upper level 
moisture approaches from the northwest. Frontal system coming ashore over 
Pacific northwest this afternoon...and associated short waves ahead of system...will 
cause clouds to be on the increase from west to east for our 
overnight hours. As disturbance approaches tomorrow...surface pressure 
gradient will tighten up some so can expect some breezy conditions 
over higher...open terrain. Upper level support for disturbance... 
especially jet stream...will move further north Saturday leaving mostly 
cloudy skies for Utah/Colorado to contend with. Cloud cover will not 
be as widespread over southern areas. 


With all that being said...lowered pop/quantitative precipitation forecast quite significantly through 
entire short term while keeping in schc precipitation Sat night for northestern 
Utah/northwestern Colorado...with schc for cen/northern mountains the occnl stray shower or 
flurry still possible Sat night into Sun morning warranting slight 
mention. For late Sun morning onwards...removed any mention of 
precipitation as weak Flat Ridge moves over area. 


Temperatures through short term will remain quite seasonable for this time of 
year. Daytime temperatures might be a few degrees cooler as clouds 
inhibit much of a warm up...though nights will be slightly warmer 
also because of incd cloud cover. 


Long term...Sunday night through Friday... 


A better chance of precipitation is expected Sun night into Monday 
morning as a stronger upper trough crosses NE Utah and northwest Colorado. 
Associated cold front moves in from the northwest Sunday evening and pushes 
across the forecast area by Monday morning. Frontal lift and dynamics 
followed by northwest orographic flow should produce at least areas of snow 
for the northern and central mountains Sun night into Monday morning. Limiting 
factor is again moisture...especially across southeast Utah and SW Colorado where 
the least chance exists...so hesitant to get too bullish with probability of precipitation at 
this time. Rapid warming aloft Monday afternoon should cause precipitation 
to end quickly save for some lingering showers possible near The 
Divide. 


Northwest flow then expected for the remainder of the week as an upper ridge 
gradually builds in for midweek. Disturbances in the flow 
periodically brush the area but with moisture lacking...dry 
conditions should prevail Tue-Fri. Cooler temperatures Tuesday on a warming 
trend. 


&& 


Aviation... 


VFR conditions will continue for the remainder of today and 
into tonight. Ridgetop winds will increase somewhat during the 
afternoon and evening especially over NE Utah and northwest 
Colorado. 


&& 


Gjt watches/warnings/advisories... 


Colorado...none. 
Utah...none. 


&& 


$$ 


Short term.....Tgr 
long term......jad 
aviation.......tgjt