269 
fxus65 kgjt 202054 
afdgjt 


Area forecast discussion 
National Weather Service Grand Junction Colorado 
253 PM MDT Sat Mar 20 2010 


Short term...today through Monday... 


A strong ridge will bring dry and stable conditions across eastern 
Utah and western Colorado through Sunday night. With Crystal clear 
skies tonight...rapid radiational cooling will occur and strong 
surface-based inversions will form. Believe model low temperatures are a few 
degrees too warm for tonight. The strong inversion will be tough to 
burn off Sunday so held maximum temperatures down a bit. The upper Ridgeline 
will pass overhead Sunday afternoon. This will open up the flow from 
the west for the next storm. 


The ridge will continue to flatten and move east Sunday night as the 
next pacnw trough moves into the western Great Basin and northern 
rockies. High clouds should start increasing Sunday afternoon through 
Monday. The flow aloft will become zonal and strengthen as the trough 
flattens the ridges and presses it south. The NAM has the surface 
cold front over slc about noon Monday. It enters NE Utah late in the 
afternoon. Have increased clouds from northwest to southeast Sunday through Monday 
and introduced low probability of precipitation for the eastern Uinta mts Monday afternoon. 


Long term...Monday night through Saturday... 


Models consistent in closing off a 500 mb low over Utah on Tuesday as the 
southern end of the split trough drops southward. Differences in 
location with 12z GFS locating 500 mb low over western Utah and 12z NAM over 
NE Utah...with 12z ec in between. Low/trough drops into Arizona Tuesday 
night/Wednesday and then tracks into nm. In general terms...this storm 
looking similar to the one that just passed except perhaps not as 
cold. 


Southwest to northeast oriented 700 mb front/baroclinic zone slides 
over NE Utah/northwest Colorado Monday night as the trough digs into Utah...and will 
likely be the focus for the heavier precipitation. Southward progression 
of the front slows Tuesday and weakens as the low wraps up to our west. 
500 mb trough axis passes later on Wednesday...and northerly orographic 
flow into the central and SW San Juan Mountains may keep snow showers 
going into Wednesday evening. Accumulating snow probable in the mountains 
with this storm...with a chance of rain/snow in the valleys. 
Previous shift raised probability of precipitation across the forecast area for Tuesday-Wednesday and 
this continues to look good. 


Mostly dry weather expected Thursday-Friday as a broad but fairly Flat Ridge 
of high pressure slides overhead. Temperatures will moderate after a bit 
of cooling Wednesday. 12z GFS and ecwmf both show another trough moving 
across our area Friday night and Sat for the next chance of 
precipitation. 


&& 


Aviation... 
VFR conditions under clear skies will prevail tonight and Sunday. 


&& 


Gjt watches/warnings/advisories... 


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


&& 


$$ 


Short term...cjc 
long term....jad 
aviation.....Cjc