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fxus65 kbou 131046 
afdbou 


Area forecast discussion 
National Weather Service Denver Colorado 
345 am MST Sat Mar 13 2010 


Short term...a stable dry airmass will be in place over the County warning forecast area as 
a ridge over high pressure sits over eastern Colorado today. The 
next system...making its way into the Pacific northwest today...is 
expected to drop into southwestern Utah by 06z tonight. As it does...the ridge 
axis will move to the east...and middle and upper level moisture will 
increase from the west. A weak difluent southwesterly flow aloft will be over 
the region...with weak qg ascent developing. The trough is expected 
to approach the four corner area by 12z Sunday as it is prognosticated to 
continue to the southeast. In the mountains...not much in the way of 
orographics for the mountains tonight...with the strongest qg ascent 
expected to pass to the west and south of the northern mountains for 
this reason...will go with just slght chance of snow with the 
exception of zone 31...chance probability of precipitation there. A Denver cyclone along the 
Front Range is expected to advect stratus/fog into the urban 
corridor late tonight. This already included in the grids so no 
changes at this time. 


Long term...upper level low over southern Utah will dive 
south-southeast into southern New Mexico by Monday morning. A 
surface low will form over New Mexico and move off into Texas by 
Monday as high pressure builds in from the north. This pattern will 
cause southeast flow to develop over the plains Sunday morning. Low 
level moisture will be pulled into the area and expect low clouds 
and fog to form Sunday or late Saturday night. The southeast flow 
will also cause a Denver cyclone to develop. Because of the 
increased cloud cover...highs will be cooler Sunday. Most of the 
lift associated with this system will remain over the foothills and 
mountains...thus expect most of the precipitation will be focused 
here. Upslope flow over the foothills and Front Range will help 
showers develop. Airmass will also be unstable over the higher 
terrain so may see some localized heavier snowfall rates under the 
convective snow. Expect to see a few inches of snow in the mountains 
south of I-70. All models show at least a quarter inch of liquid 
over this area...while the NAM and sref have over a half inch. Snow 
will taper off Sunday night and should come to end by Monday morning. 


Mild and dry conditions will prevail Monday through Wednesday as the 
upper level ridge redevelops over the central rockies. Highs will 
climb above normal Tuesday. Expect to see our first 60 degree day in 
a long time Tuesday or Wednesday. Warmest day of the week looks to 
be Wednesday. 


Flow aloft will become westerly by Wednesday night as a strong upper 
level trough moves south over the northern rockies. This will bring 
cooler temperatures and a slight chance for precipitation. The upper 
level trough continues to dig south into Friday. Will continue to 
have probability of precipitation in the forecast for this through Friday night. Models are 
still out of whack on how this system evolves. However...both the 
GFS and European model (ecmwf) show a good shot of cold air. On Friday afternoon... 
both models show -12c for 700mb temperatures. 



&& 


Aviation...VFR conditions expected over the next 18-24 hours. 
Stratus/fog will advect into the region overnight with a Denver 
cyclone in place. IFR conditions will likely develop with ceilings 
under 1000 feet/visibilities less than 1/2 mile around 12z Sunday and 
continue through much of Sunday morning. Some light drizzle/rain 
showers may develop after 12z Sunday as well. 
&& 


Bou watches/warnings/advisories...none 


$$ 
Cooper/meier