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fxus65 kgjt 022134 
afdgjt 


Area forecast discussion 
National Weather Service Grand Junction Colorado 
234 PM MST Tuesday Dec 2 2008 


Short term...tonight through Thursday... 


Pacific shortwave that was over southern Idaho at midday is on track to drop 
across eastern Utah/western Colorado tonight. Surface front/trough moving into NE Utah 
is expected to reach a Craig-Moab line by about 5pm-6pm but weaken as 
it moves across the remainder of western Colorado by midnight. Not 
much precipitation associated with this feature at the moment... 
though its encounter with the mountains should generate some precipitation in 
conjunction with a period of dynamics and instability this evening. 
Most precipitation appears associated with the cold pool aloft 
moving into northwest Utah...which doesn/T move overhead until late evening. 
Northwest flow about 20 kts should then provide some orographic snows to 
favored areas late tonight through Wednesday morning. System as a whole 
looks a bit weaker and drier than it did yesterday...and appears to 
be losing some identity and moisture per satellite pics to a larger 
system dropping out of western Canada. Elected not to issue any 
winter highlights for tonight due to weakening nature of the front 
and shortwave. Snow amounts for the northern and central Colorado mountains generally 
4-7 inches through Wednesday morning...just below advisory amts. Coldest 
air with that Canadian system should stay east of The Divide. 


By Wednesday afternoon...activity over those favored areas will have 
diminished except for perhaps some light snow in the northernmost 
Colorado mountains high temperatures Wednesday will be several degrees cooler than today. 
The proverbial fly-in-the-ointment is the persistent west to 
northwest flow into the northern mountains models keep this flow fairly 
moist...so could see periods of light snow for the Elkhead/park/Gore 
ranges through Thursday. Another wave dropping down across the Pacific northwest 
begins to stretch/shear apart in a SW to NE orientation. 


Long term...Thursday night through Tuesday... 


A short wave over northern Colorado shears apart as some energy digs to 
the southwest...while the remainder of the energy slips into the 
plains. Still expect scattered mountain showers over the north... 
although a general lack of forcing with little or no cold advection 
or jet support and only marginal orographics. Stabilization and 
drying occur Friday for only a few lingering flurries over the higher 
northern mountains high pressure along the West Coast amplifies a bit 
Saturday in response to closed low off California edging eastward. 


Sunday through Tuesday...GFS and ec part ways with ec lifting closed 
low northeast into the southwest...while the GFS keeps this feature 
offshore. HPC guidance very close to GFS and accepted. As such a 
decrease in probability of precipitation occur from previous thinking as most energy 
remains either north or south of the County Warning Area. 


&& 


Aviation... 


A cold front approaching kvel at 21z will reach a kcag-kcny line by 00z 
then weaken as it moves southeast across western Colorado by midnight. Expect lowering 
ceilings across NE Utah/northwest Colorado late this afternoon...and across west-central 
Colorado by 00z. MVFR conditions will develop over the mountains with areas of 
IFR ceilings and visibility in -sn after 00z. Mountain tops ocnlly obscured. Periodic 
MVFR ceilings are possible at Mountain Valley airports...including 
ksbs...kege...and kase tonight. Ceilings will be improving between 15z- 
19z Wednesday. 


&& 


Gjt watches/warnings/advisories... 
Colorado...none. 
Utah...none. 


$$ 


Short term.....Jad 
long term......mc 
aviation.......jad