Weather

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Area forecast discussion 
National Weather Service Sacramento California 
330 PM PDT Friday Aug 29 2008 


U/L Ridge still dominating the north state. According to water 
vapor imagery an area of monsoonal moisture over the area is 
starting to switch from a northwest direction to north...indicating that we are 
definitely on the back side of the ridge. The gradients have 
settled down and we noticed that as the acv-rdd gradient became 
stronger than the mfr-rdd...the north wind shifted to a southeast wind over the 
SAC valley. Expect the sfo-vcb gradient to tighten a bit tonight 
and bring more of a Delta breeze. The marine layer stratus is 
starting to fill in along the coast but is not reflected on The Fort 
Ord profiler because the profiler is still in the clear area of 
Monterey Bay. However with the marine layer thickening a bit 
overnight expect temperatures to respond...temperatures could be 10-15f cooler 
across the valley and lower foothills Sat but not quite as a 
dramatic drop over the higher Sierra. Sun will cool even further as 
a short wave from the parent goa low drops into the north state with 
h50 temperatures around -20c. This will cause maximum temperatures on sun to drop 
another 10-15f...lowering temperatures some 20-30f from today to sun. 
Overnight sun temperatures will potentially drop to near freezing over 
higher ridges and some mountain valleys. As the short wave digs southeast 
across our area later on sun...a jet core of around 110kt will help 
to enhance the strong 10mb mfr-SAC gradient that is forecast to set 
up. The 12z Gem/GFS/ECMWF are all consistent with tracking the u/l 
low southeast across the north state into Nevada by Monday morning. So with 
northerly flow up through the atmos...we should expect strong surface winds 
to continue through Monday as the surface high builds over Oregon and creeps 
towards the western Great Basin. Jclapp 


Extended discussion (tuesday through friday)... 
dry northwesterly flow will develop over California for the extended 
as an offshore ridge pushes eastward from the Pacific. Latest GFS 
runs are trending slower...with the trough moving eastward out of 
the region late Monday night. Expect continued breezy winds with a 
strong surface gradient and 850 mb/700 mb cold air advection Monday night into 
Tuesday morning. The gradient shifts from the north to the northeast 
by daybreak...with gusty winds through Northeast Mountain canyons 
can be expected. The possibility of critical fire conditions due to 
winds and poor overnight humidity recoveries continues through 
Tuesday morning...with a Fire Weather Watch in effect. The winds are 
expected to decrease some through the afternoon. High temperatures 
Tuesday are expected to reach the low to middle 90s...which is average 
for this time of year. The latest runs of the GFS and European model (ecmwf) both 
show the gradual warming trend continues through the rest of the 
week as the eastern Pacific Ridge amplifies. A broad weakness in 
heights remains over northern California east of the trough. The 
surface pressure gradient will bring continued northerly winds 
through the rest of the week...although they will not be as strong 
as earlier in the week. This airmass remains quite dry with no 
precipitation anticipated. 




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Aviation... 
VFR conditions expected tonight and tomorrow. Winds will be 
generally light except gusty southwest winds over higher mountains 
Saturday afternoon and evening. Scattered cumulus clouds over the 
northern Sierra and scattered high clouds elsewhere this evening. 


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Sto watches/warnings/advisories...Fire Weather Watch for the 
northern and central Sacramento Valley and the adjacent mountains 
and foothills for Sunday 5 PM EDT through Tuesday morning 11 am PDT. 






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