532 
fxus65 kbou 210824 
afdbou 


Area forecast discussion 
National Weather Service Denver Colorado 
220 am MDT sun Mar 21 2010 


Short term...upper level ridge of high pressure will continue to 
build across Colorado today with a very dry and stable airmass in 
place. There is still some decent north-northwest flow aloft according to 
profilers and higher mountain peaks/east slopes are still showing 
some gusts upwards of 50kt. These gusts should diminish during the 
day as the ridge moves over US and flow aloft diminishes. As the 
ridge flattens later tonight ahead of next Pacific wave...the westerly 
flow will increase again. Cross sections show 30-35kt of cross 
barrier flow and will likely result in some winds increasing in the 
mountains again later tonight up to 50kt and 20-30kt in the foothills. 


Sunny skies expected today with a some increase in high level 
moisture late today and tonight with some wave clouds expected. 
Much warmer temperatures today as 700mb temperatures climb to almost +1c at 
Denver. Warmest readings on the plains with some slowing of the 
warming in/near the foothills under snow cover. Current temperature grids 
reflect this. 


Long term...a flat upper level ridge will be over the area on Monday 
with west-southwest flow aloft ahead of an upper level trough approaching from 
the northwestern US. With low level west-southwest downslope flow in place temperatures should 
warm up nicely by afternoon with highs in the 60s across northestern Colorado. Overall 
should see a dry day although some middle and high level moisture will 
move in by late afternoon. For Monday night and Tuesday there is fairly good 
consensus among the medium range models that an upper level low will 
move into The Four Corners area by Tuesday afternoon or evening. Meanwhile a 
cold front will move into northestern Colorado by 12z Tuesday and then push across the 
entire area by midday. Both GFS and NAM show upslope flow through the 
day with favorable qg ascent and lapse rates so precipitation potential 
should gradually increase in most areas through the day. Best chance 
initially will be in the higher terrain will be north of I-70 at at 
lower elevations closer to the Wyoming-Colorado border area and then spread 
southward by afternoon across the rest of the area. Soundings show wet 
bulb zeros lowering to 5500 feet by Tuesday afternoon so precipitation could be all snow 
by afternoon along the Front Range with a mix over the plains. 


For Tuesday night should still see a good chance of snow in the mountains and at 
lower elevations with the best chance along and near the foothills and 
over the Palmer Divide as upslope flow deepens as favorable qg 
vertical velocities continue over the area. Overall set up is not 
as strong as previous event however could still see at least advisory 
amounts in the mountains east of The Divide...in the foothills and over 
the Palmer Divide. At lower elevations amounts will depend on 
timing of heaviest precipitation and whether it occurs before or after sunset 
however could see from 2-4 inches especially on grassy areas. For 
Wednesday there is some disagreement on location upper level low as the 
GFS weakens it and moves feature as an open trough across southern Colorado 
while the Canadian and European model (ecmwf) moves the system much further south 
across central and southern New Mexico. However all models show weakening 
upslope flow across northern Colorado in the morning with decreasing qg 
vertical velocities so it appears precipitation should gradually end Wednesday 
morning in most areas. Highs on Wednesday will depend on how fast precipitation 
ends and cloud cover breaks up. If skies clear by afternoon readings 
would probably be in the 40s across northestern Colorado. 


By Thursday and upper level ridge will build over the area with a drier 
airmass and moderating temperatures as readings should rise back to 
seasonal levels. On Friday a flat upper level ridge will be over the 
area although another upper level trough could affect the area by Friday 
night into Sat an bring a chance of snow to the mountains over lower 
elevations a cold front may affect northestern Colorado Friday night into Sat bringing 
cooler temperatures and a slight chance of precipitation. 




Aviation...VFR with mainly clear skies today...then some high level 
moisture increasing tonight. Diurnal wind patterns this am then shifting 
southeasterly this afternoon. Speeds generally under 12kt. At bjc later tonight 
may see some gusts up to 20kt from the west with the increasing 
westerly flow. 


&& 


Bou watches/warnings/advisories...none. 


$$ 


Swe/rpk