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Area forecast discussion 
National Weather Service Grand Junction Colorado 
400 am MST Sat Nov 21 2009 


Short term...today through Sunday night... 


The first in a series of waves has moved over the forecast area 
early this morning...and will continue to bring nothing more than an 
increase in clouds through today. Energy/moisture associated with 
this impulse will mainly stay to our north. The next wave will be 
just a little stronger and again stay mainly to our north. However... 
this impulse is just a little stronger and colder. Along with the 
increased clouds...the chance of snow will develop over the northern 
mountains this evening...mainly near the Continental Divide. 


The pattern will remain progressive through the short term period 
with a fast moving ridge sweeping by on Sunday. Then late Sunday the 
last and strongest shortwave of the series will move into the area. 
Again the main focus of this system will stay to our north. But 
enough energy will dip into our forecast area for the chance of snow 
to spread across all the Colorado mountains and into the northern 
valleys. The best timing is for Sunday evening as an associated 
surface cold front sweeps across the forecast area. The previous 
forecast on the right track so made only minor changes for this 
package. 


Temperatures will remain quite seasonable for this time of year. Daytime 
temperatures will drop a few degrees as clouds inhibit much of a warm up... 
though nights will be slightly warmer also because of better cloud 
cover. 


Long term...Monday through Friday... 
Monday...northwest flow behind departing trough should bring some 
orographic snow to the northern Divide mountains. Cold advection 
appears weak with the cold pocket staying north of Colorado... 
therefore the air mass may stay somewhat stable despite northwest flow. 
This would limit snow production and the models seem to agree as quantitative precipitation forecast 
over the northern Divide mountains is low and ends by by evening. 


High pressure builds into the Great Basin with ridge axis extending 
to the Canadian plains. This will keep the forecast area dry 
through the long term period with a slow warming trend. By Friday 
the GFS and ec diverge significantly with the ec showing a digging 
trough into Nevada and Utah. The GFS solution shows a short wave 
flattening the ridge but keeps the forecast area dry. No changes to 
the dry forecast until models show better agreement. 


&& 


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.....Eh 
long term......pf 
aviation.......tgjt