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fxus66 ksto 201053 
afdsto 


Area forecast discussion 
National Weather Service Sacramento California 
330 am PDT Sat Mar 20 2010 


Discussion... 
ridge of high pressure over the area this morning but will shift to 
the east during the day today as a trough of low pressure digs over 
the eastern Pacific. Patchy fog has developed in the northern San 
Joaquin Valley this morning under light winds and subsidence under 
the ridge. The patchy fog should dissipate before 10 am. High clouds 
ahead of the trough will bring mostly sunny skies today. 
Temperatures are expected to be about the same to 5 degrees cooler 
in most locations today with a cooler air mass moving into the 
region. Although the northern San Joaquin Valley and adjacent 
foothills may be about the same to a couple degrees warmer. 
Temperatures will be about 6 to 12 degrees above normal for the 
first day of Spring. Spring officially begins at 1032 am this 
morning. Happy Spring! 


The weather will change on Sunday as the the trough of low pressure 
moves into the Pacific northwest and brushes by northern California. 
This will bring more clouds and cool temperatures down to near 
normal on Sunday along with a slight chance of precipitation to the 
northern mountains Sunday into Sunday night. Precipitation is 
expected to be light with system (generally less than a tenth of an 
inch) due to most of the dynamics staying to the north and not much 
moisture (pws only around a third of an inch). Snow levels are 
expected to be around 6000 feet on Sunday and drop to around 4000 to 
5000 feet Sunday night as the light precipitation diminishes. 
This system moves to the east on Monday with northerly winds and dry 
weather developing behind it. Mfr-SAC gradient expected to increase 
to around 8 mb on Monday into Monday night bringing northerly winds 
of 10 to 25 miles per hour with local gusts to around 35 miles per hour. The gradient 
turns more easterly Tuesday morning with the SAC-rno gradient 
increasing to 5 mb which will bring locally gusty northeasterly 
winds to around 40 miles per hour to the favored northeast-southwest oriented 
canyons and ridge tops in the mountains along the east side of the 
County Warning Area. At this time it looks like the winds will be below advisory 
criteria. 


Another system may brush by far northern California Wednesday night 
and possibly into Friday. This will mainly bring a slight chance of 
precipitation to the northern mountains. Although the models vary 
with the strength and track of these systems. The GFS tracks most of 
the system further north so it is drier over northern California. 
The European model (ecmwf) tracks it further south bringing more precipitation and 
extending it down to the Interstate 80 corridor on Friday. The 
current forecast favors the drier solution of the GFS. Saturday 
looks dry at this time with ridging in between systems. The next 
system may come in Sunday bringing another threat of precipitation. 
Hso 


&& 


Aviation... 
high pressure weakens as low pressure approaches the region from the 
Pacific. Variable hi clouds expected as the flow aloft shifts to 
southwest by afternoon. Limited MVFR 5sm br in the northern San 
Joaquin Valley this morning otherwise VFR broken-ovc250 most areas. 
Isolated -shra possible at krdd tomorrow. Snow grains 


&& 


Sto watches/warnings/advisories...none. 


&& 


$$