136 
fxus65 kgjt 172155 
afdgjt 


Area forecast discussion 
National Weather Service Grand Junction Colorado 
354 PM MDT Wednesday Mar 17 2010 


Short term...tonight through Friday... 


Ridge axis is overhead this afternoon bringing temperatures 3-5 
degrees above normal. The ridge gets flattened tonight then pushed 
east on Thursday as a deepening trough drops in from British 
Columbia. High cloud ceilings today and breezy SW-west flow Thursday 
will keep temperatures above normal. 


Models continue a trend of an open and more progressive trough. 
Frontal passage will be quite strong across the north Thursday 
evening...then weakens as it passes south of I-70 overnight. 100kt 
jet nose drops into NE Utah early Friday providing upper level 
support across the north. The 18z run brushed the northwest Colorado mountains with the 
-30c cold core with 700mb temperatures dropping to -10c. Northeast flow on 
Friday will limit snowfall in the northern valleys but instability 
showers will continue favoring the Continental Divide. 


Long term...Friday night through Wednesday... 
a northerly flow and cold advection will continue into Friday night 
along with moderate low level moisture. Unstable lapse rates will 
allow accumulating snow to continue over the northern and central mountains 
near The Divide...decreasing some after midnight. In coordination 
with the short term forecaster raised probability of precipitation over the north to coincide with 
winter hilites which extend through 12z Saturday. However 700 mb easterly 
flow is causing both of US some anxiety. By Saturday showers will 
have tapered off to the isolated category...and these will mostly 
be confined to the northern and central mountains in the mean time a high 
pressure ridge will build to our west over the Great Basin. 


The ridge will shift ewrd over our region Sunday bringing dry mild 
conditions...but the next Pacific weather system will already be 
entering the northwest states. Monday will be a transition day as the 
ridge gets flattened as depicted by the GFS. The ec is more 
amplified with a slower progression with the next weather system. Either 
way both indicate dry mild conditions. The next storm system arrives 
Tuesday and have raised probability of precipitation to the scattered category over the 
mountains this storm hangs around through Wednesday then begins to exit 
the region. 


Temperatures will drop to 10 degrees or more below normal on Friday 
with little recovery indicated for Saturday. However...the building 
ridge will bring afternoon highs toward normal by Sunday and Monday 
before cooling comes with the next storm Tuesday. 


&& 


Aviation... 


VFR conditions will continue under a high pressure ridge tonight. The 
ridge breaks down Thursday as a storm approaches from the northwest. 
Breezy southwest pre-frontal winds and scattered showers will develop 
in advance of the storm during the afternoon...mainly north of the I- 
70 corridor. In spite of shower activity...VFR conditions are 
expected to prevail at most locations. 


&& 


Gjt watches/warnings/advisories... 


Colorado...Winter Storm Warning Thursday 6 PM MDT through Saturday morning 
6 am for zones 4/10/13. 
Winter Weather Advisory midnight Thursday night through 6 PM 
Friday for zones 3/9/12/17/18. 
Utah...Winter Storm Warning Thursday 6 PM MDT through Friday 6 PM for 
zone 23. 


&& 


$$ 


Short term...Joe 
long term....mc 
aviation.....Mc