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fxus65 krev 211135 
afdrev 


Area forecast discussion 
National Weather Service Reno Nevada 
335 am PST Sat Nov 21 2009 


Short term... 


Krgx radar loop is indicating a narrow band of probable snow 
showers north of Pyramid Lake...while farther north light snow is 
likely occurring in far northwestern Nevada and Surprise Valley. Nearby 
observations from Alturas reported light snow while mesowest data 
from Cedarville and feet Bidwell have accumulated 0.01 to 0.02 inch 
of precipitation per hour since late Friday evening. Weak secondary vorticity 
center moving across northern California on water vapor satellite loop appears 
to be the force behind this light snow. This feature will exit the 
region by daybreak so any leftover snow showers should wind down 
during the next couple of hours. The forecast will include mention 
of isolated snow showers through 15z for a small part of northwestern Nevada. 


Otherwise today will be dry and cool with temperatures only reaching the 
40s across most valleys today. High clouds will be on the increase 
as another weaker shortwave approaches the northwestern US tonight. 


This system will have little moisture to work with and only isolated 
snow and rain showers are expected for parts of northestern California-northwestern Nevada 
and portions of the Tahoe basin late tonight through Sun morning. 
Little or no snow accumulation is expected with this system...with 
the most significant effect being increased winds. 700 mb flow 
briefly reaches 50 knots between 12z-18z Sunday which would produce a 
notable increase in ridge winds. While the peak speeds are 
unlikely to come close to the 100+ miles per hour values that occurred 
yesterday...the potential exists for 70-80 miles per hour gusts in higher 
elevations for a few hours Sunday. With some mixing likely Sunday 
afternoon...winds have also been increased for lower elevations 
mainly north of Highway 50 with gusts 35-40 miles per hour. Lake Wind Advisory 
will likely be necessary for both Tahoe and pyramid unless next 
run of guidance backs off on the 700 mb flow. Maximum temperatures will be a 
few degrees warmer than today due to this mixing...which will 
partially offset the cold air advection behind the shortwave. 


For sun ngt-Monday...ridge will build over California-Nevada and produce 
generally light winds and dry conditions over the region. 
Weak NE surface flow and warming middle level temperatures will produce 
inversion conditions resulting in limited heating for valleys but 
push temperatures in higher elevations up several degrees from Sunday. 
Mjd 


Long term...Tuesday through Friday... 


Models remain in good agreement with ridge building over the west as 
the pattern over North America amplifies. Ridge axis should progress 
into the eastern Great Basin and The Rockies by Thursday or Friday. 
This will allow Pacific energy to enter the West Coast...for a low 
chance of rain and increased winds late next week. 


Temperatures to remain near normal in the Nevada valleys...with 
slightly above normal readings in the Sierra with the high pressure 
aloft. Ridge will maintain inversions in the Nevada valleys with 
light north to northeast flow to prevent a more significant warming 
trend. 


European model (ecmwf) remains more consistent and aggressive with energy entering 
the West Coast late in the week. Thus have left the low chance or 
rain/snow across the northern areas Thursday night into Friday. GFS 
and it ensembles are farther north with the energy...with a warmer 
and drier solution for the Sierra and western Nevada. Both European model (ecmwf) 
and GFS would support some potential for breezy to windy conditions 
Thursday night and Friday. Brong 


&& 


Aviation... 


Northwest flow will affect the area Saturday and Sunday as a system 
passes north of the area. Rain/snow showers are possible in the 
Sierra and for areas north of I-80. Increase in moisture should 
bring MVFR ceilings to the Sierra with mountain obscurements. 


Winds may increase after 08z tonight as system passes through 
Oregon. Gusts in the valleys could reach 30kts early Sunday 
morning...with the northern Sierra ridge winds near 40-50 kts. Brong 


&& 




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


$$ 


Http://weather.Gov/Reno