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Area forecast discussion 
National Weather Service Las Vegas Nevada 
350 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. 
&& 


Short term...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. 
&& 


Aviation...for McCarran...an area of low pressure will push a weak 
cold front through the Las Vegas Valley....with the best estimate 
for frontal passage through McCarran around 10 am this morning. 
Behind the front...the current gusty south southwest winds will 
swing to the northwest...and persist the remainder of the day. Winds 
behind the front will not be as strong as the prefrontal winds...but 
should average around 10kts. As the surface high builds in north of 
the area...winds should change over from northwest to northeast by 
late afternoon. Any cloud cover will remain scattered and above 
15kft. 


For the rest of southern Nevada...northwest Arizona...and southeast 
California...the main concern today are winds...as a weak cold front 
passing 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 scattered and 
above 15kft...as moisture is very limited with this low pressure 
feature. 


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


$$ 


Harrison/Kennedy 


Http://weather.Gov/lasvegas