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Area forecast discussion - updated 
National Weather Service Sacramento California 
515 am PST Tuesday Mar 9 2010 


Updated to cancel Winter Weather Advisory for northeast foothills 
and western Plumas County/Lassen park 


Discussion... 
cold front moving across interior California into the Sierra this 
morning. Blended total precipitable water satellite imagery shows 
that the moisture plume feeding into this cold front has sunk 
southward along the coast...near the Mendocino/Sonoma County line. 
Current radar shows most shower activity along the Sierra and 
foothills south of Highway 70 with some lingering showers along the 
eastern side of the Central Valley. 


Decided to cancel the Winter Weather Advisory for the coastal range 
and Shasta County since precipitation has diminished as moisture 
heads southward. 


Update: just canceled advisory for the northeast foothills of 
Sacramento Valley...western Plumas County/Lassen park area since 
showers have moved southward. 


Temperatures warming a bit today as the upper level trough and 
associated cold air moves southeastward. Valley highs today will 
range in the middle 50s up to 60 degrees f...as opposed to yesterday's 
highs in the low to middle 50s. Clearing skies with drier and warmer 
weather today due to upper level ridging building into northern 
California. Fairly clear skies overnight will allow enough 
radiational cooling overnight that patchy frost may be possible 
tomorrow morning. 


The next storm is currently located between 140-150w and just south 
of 50n over the Pacific Ocean. This system will move inland on 
Thursday bringing a slight chance to chance of rain into our coastal 
range by Thursday night. Rain and snow probabilities greatly 
increase by Friday morning as precipitation spreads across our 
entire County Warning Area. Snow levels initially starting around 5000-6000 feet 
Thursday will lower towards 3000-4000 feet on Friday. Quantitative precipitation forecast estimates 
look more impressive with this system...moderate to heavy snow 
accumulations possible. Valley rain totals could be up to around 
half an inch. Rain and snow will linger into early Saturday morning 
followed by yet another upper level ridge developing by Saturday 
afternoon. Jbb 




Extended discussion (sunday through wednesday)... 
the early portions of the extended period will be dominated by a 
building ridge of high pressure over the southwestern US. With this 
dry pattern and warming airmass...will likely see widespread 70s 
along the valley floor for the first time this season on Monday if 
not by Sunday. Upper 60s to near 70 will also be possible for 
foothill locations with 50s and 60s for the higher elevations. 
Warmer than normal conditions should continue for most locations 
through Wednesday. Medium range models hint at a Pacific system 
perhaps bringing light precipitation to areas north of Interstate 80 
during the middle of next week. Dang 


&& 


Aviation... 
frontal system has moved to the south and east of the forecast area. 
Rain and snow showers along the west slopes of the northern Sierra 
linger...bringing widespread IFR/LIFR conditions with snow levels 
down to around 1500 to 2000 feet. Expect gradually improving 
conditions along the Sierra by 18z. Periods of IFR ceilings possible 
at the taf sites through around 17z then improving to VFR. Winds 
will become northwesterly up to 10kt during the day. 


&& 


Sto watches/warnings/advisories... 


Winter Weather Advisory until 10 am PST Wednesday above 2000 feet 
for the motherlode...West Slope northern Sierra Nevada. 


&& 


$$