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Area forecast discussion 
National Weather Service Las Vegas Nevada 
955 am PST Sat Nov 21 2009 


Synopsis...the region will be under a dry northwest flow through 
Monday. Some high clouds will drift through from time to time and 
locally gusty north winds are possible today and again on Sunday 
night and Monday as upper level disturbances brush the area. 
Temperatures will be fairly close to normal through Monday. 
&& 


Update...weak frontal boundary moved through McCarran Airport 
between 8 and 9 am. Front will continue to slowly work south this 
morning before washing out across southern Mohave and San Bernardino 
County this afternoon. Temperatures will be several degrees cooler 
behind the front today. In morning update will massage the winds and 
remove the mention of morning. 
&& 


Aviation...for McCarran...this mornings frontal passage has brought 
the winds over to the northwest. They should remain 10 knot or less 
today and gradually veer over to the northeast later in the 
afternoon. This evening and over night they will go to the 
southwest. Any cloud cover will remain few to scattered and above 
20kft. 


For the rest of southern Nevada...northwest Arizona...and southeast 
California...the main concern today are winds...as a weak cold front 
passes through the area today. Strong southwesterly winds can be 
expected prefrontal...with winds decreasing and switching to the 
north behind the front. Any cloud cover will remain few to scattered 
in coverage and above 20kft. 
&& 


Previous discussion...250 am PST Sat Nov 21...upper trough which 
brought windy conditions to many areas yesterday and last night will 
move east of the area today. Gusty southwest winds have been 
dropping off early this morning and will cancel/expire the wind 
advisories. Some locally gusty north winds are possible in a few 
areas today behind the trough but nothing near advisory criteria. 
Temperatures today are tricky to forecast as current temperatures 
are way up but cooling was expected behind the trough. Raised 
inherited temperatures up a bit to account for the warm start to the day 
and generally went with a compromise between AVN and nam12 MOS 
guidance. Dry northwest flow continues Sunday as another trough 
moves into Idaho and northeast Nevada. Main moisture with this 
system will stay north and just expect some high clouds. Dry 
northwest flow will persist Monday but temperatures may be a few 
degrees cooler behind the aforementioned trough and a reinforcement 
of northerly winds which could be a little gusty...especially down 
the Colorado River valley. 


Long term...models remain in good agreement up through Thanksgiving 
day...so minimal change was needed to the existing forecast. The 
Gem...GFS...and European model (ecmwf) all indicate ridging across the area through 
the middle of the week...resulting in temperatures slightly above 
normal by middle week and light winds predominantly out of the north 
during the late morning and afternoon as the surface high persists 
across the northern Great Basin. There are still major differences 
in guidance next Friday and beyond...with the GFS indicting ridging 
and the ec and Gem showing a rather deep trough. Decided to play the 
climatology card this far out...but if the Gem/ec solution show any 
continuity...and more GFS ensemble members trend that way...will 
definitely have to drop temperatures and increase probability of precipitation by the end of 
next week and into the weekend. 
&& 


Vef watches/warnings/advisories... 
Nevada...none. 
Arizona...none. 
California...none. 
&& 


$$ 


Pierce/Jacques/Harrison/Kennedy 


Http://weather.Gov/lasvegas