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fxus65 krev 081200 
afdrev 


Area forecast discussion 
National Weather Service Reno Nevada 
400 am PST Thursday Jan 8 2009 


Short term... 
tricky temperatures already this morning as fast moving system 
approaches the Oregon and far northern California coast. Winds 
have increased to 30-50 miles per hour with gusts to 60 miles per hour over ridgetops... 
which is mixing up many but not all valleys. For instance...it is 
still in the low to middle 30s around downtown Reno and Sparks but in 
the 40s just off the valley floor in southwest Reno and in the 
north valleys of Reno. All valleys except those in Mono and Mineral 
counties should commence mixing shortly (which will send the temperatures 
up some 10-15 degrees) as stronger winds aloft and a developing 
surface gradient do away with the shallow inversions. 


Precipitation wise...approaching system still on track to drop some light 
precipitation today across the far northern and western portion of the 
County Warning Area. With the main forcing from far northern California and Nevada 
into Oregon...moisture looks rather anemic/shallow south of about 
a Portola to Gerlach line...so precipitation will have a hard time making 
it past the Sierra crest south of Plumas County. Wind wise...it 
will get breezy today for a few hours ahead of the front but I am 
not expecting abnormally strong winds (mostly 40 miles per hour or less) in 
the Lee of the Sierra despite strong winds over the ridgetops. 


System pulls east of the entire County Warning Area by early evening...with a 
ridge of high pressure building strongly overhead through the 
remainder of the short term forecast. Slackening winds aloft and a 
building surface high of around 1040 mb over the Great Basin will 
bring a return to inversions and colder...more typical January 
temperatures for valleys Friday and Saturday. Snyder 


Long term...Sunday through Wednesday... 
mean pattern during the long term will consist of amplified pattern 
of eastern North America trough and West Coast ridge centered near 
or slightly offshore. This will result in a light east to northeast 
flow and dry conditions. A few of the naefs members show light quantitative precipitation forecast 
extending from the Desert Southwest into the Sierra by midweek. This 
is most likely associated with these few solutions having a somewhat 
higher latitude ridge center and allowing some energy to undercut 
ridge. Probability of precipitation at middle week were bumped slightly toward climatology but 
left well below mentionable values. Temperatures will remain above 
normal especially in the upper elevations. Hohmann 
&& 


Aviation... 
freezing fog has had trouble forming this morning at ktrk as ridge 
level winds and mixing have been sufficient to disrupt boundary 
layer. Cold front to bring gusty winds today with ridge winds 
approaching 75kt. Satellite pictures show clouds along front 
thinning as they approach northern California. So not expecting any 
problems with ceilings/visibilities at Sierra taf sites. There may be a 
sprinkle or two along with a brief Montana top obscuration as the front 
passes. Front will move quickly out of the area tonight with 
clearing skies and diminishing winds. Some MOS guidance does show 
indication of shallow freezing fog formation around ktrk but it 
would be late tonight. VFR conds overall at area taf sites through 
this evening. Hohmann 
&& 




Rev watches/warnings/advisories... 
Nevada...Lake Wind Advisory from 10 am this morning to 6 PM PST this 
afternoon for Pyramid Lake. 


Lake Wind Advisory from 7 am this morning to 4 PM PST this 
afternoon for Lake Tahoe. 


California...Lake Wind Advisory from 7 am this morning to 4 PM PST this 
afternoon for Lake Tahoe. 


&& 


$$ 


Http://weather.Gov/Reno