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fxus65 krev 022247 
afdrev 


Area forecast discussion 
National Weather Service Reno Nevada 
300 PM PST Tuesday Dec 2 2008 


Short term... 
very few changes made to the going forecast. The low that moved 
through Oregon and into northern Nevada today continues its trek 
southeast and away from the area. Another another cut off low 
pressure system is expected to break away from the flow off the 
Oregon coast and drop south toward the central California coast over the 
next few days. At the same time...another colder shortwave is 
expected to move through eastern Oregon and Idaho and into the Great 
Basin. The low off the coast will try to tap into the colder low 
moving into the Great Basin. Models differ on extent which the 
offshore low pulls in the colder air. A colder low will be more 
dynamic in developing precipitation...not that we would receive much 
of it. Either way...right now the forecast looks dry through the 
short term. There may be some cloud cover associated with the low 
off the California coast that moves into the area from time to 
time...especially south of Highway 50. Temperatures are expected to 
be near normal the rest of the work week as the cooler air that 
moved into the region today will be reinforced by the colder 
shortwave dropping into the Great Basin. 


With the lack of precipitation...water year precipitation for the 
Tahoe basin has fallen to 78 percent of normal with snowpack 
running at just 3 percent of normal...essentially non existent. For 
every day that passes without precipitation in the Sierra...water 
year precipitation totals will continue to drop a few percent each 
day. With nothing significant coming down the pipe in the 
foreseeable future...there will be a hefty deficit to make up to 
prevent the region from seeing three consecutive years of below 
normal precipitation. Milne 


Long term...Saturday through Tuesday... 


Medium range models are showing some discrepancies over the weekend 
with the cut off low that develops off the Southern California coast later this 
week. The GFS and all of the ensemble members keep the low off the 
California coast through Sunday and if anything drift it further west 
through early next week. The European on the other hand has the low 
being picked up by an approaching trough and moving it into Southern 
California/southern Nevada on Sunday and into the Desert Southwest on Monday. The 
Canadian is closer to the GFS solution with the further south track 
of the low...but similar to the European as it does push the low 
east by Monday...just slower and further south. The Canadian has the 
low weakening as it moves over northern Baja California by Monday morning. The Euro 
solution could bring increased clouds and some precipitation to our 
southern County Warning Area...but with no support from other models with a track that 
far north with the low will leave the forecast dry for now through 
Tuesday. 


Weak flow and mild conditions with temperatures just above 
normal...or in the low 50s are expected across the area through 
Sunday. The GFS and Euro are in decent agreement that a system will 
approach the Pacific northwest coast by next Tuesday and possibly push some 
gusty west winds...and clouds or showers into northern areas. This may 
act to mix out the inversions in the lower levels and help to 
increase temperatures by Tuesday...but it is too soon to tell. There 
has not been much run to run agreement on this scenario yet with 
either model or with the ensembles. Therefore will increase clouds 
over northern areas and leave the forecast dry for now. Gmcguire 
&& 


Aviation... 


Cold front has moved south of the area leaving behind occasionally 
gusty north to northeast winds 10-15 kts at krno and klol. These 
winds will diminish by 01z across the area. Ridge winds have 
decreased this afternoon with only north 10-15 kts with gusts to 25 
kts expected through tonight. 


North to northeast flow and dry conditions tonight should keep fog 
from forming at ktrk. VFR all taf sites and light winds expected 
from tonight through Wednesday. Gmcguire 
&& 


Rev watches/warnings/advisories... 
Nevada...none. 
California...none. 


&& 


$$ 


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