Weather

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Area forecast discussion 
National Weather Service San Joaquin Valley - Hanford California 
915 PM PST Monday Jan 5 2009 




Discussion...radar indicates precipitation has pretty much ended 
over the central California interior this evening. Rainfall ranged from a 
trace to a few hundredths of an inch in the central San Joaquin 
Valley...and around a tenth of an inch in the southern Sierra north 
of Kings Canyon with a couple isolated totals around two tenths. 
Surface observation indicate overcast low clouds across the valley while 
satellite shows higher clouds continue to stream in within the 
fast northwest flow aloft. This cloud cover will moderate overnight 
temperatures and inhibit frost and fog from the valley tonight. Gusty 
winds across the Kern County mountains and deserts this afternoon 
have trended lower and will continue to diminish. No update planned 
this evening. 




From previous discussion...a strong upper ridge in the east Pacific 
centered along 140w will hold through Tuesday...then flatten out Wednesday and 
Thursday as a vigorous shortwave trough moves over the top. This shortwave 
is forecast to reach the West Coast Thursday...with the southern portion 
of the trough moving quickly through central California Thursday night. This could 
bring a few showers to the mountains...otherwise dry. Temperatures the next 
few days will warm to above normal levels for all but the 
San Jose valley...where night and morning low clouds and patchy fog will rule. 
Still a little hard to tell right now whether much if any clearing 
will occur each day. GFS guidance has the cloudiest forecast and 
elected to go with it. Thus smaller diurnal temperature changes and only 
some partial afternoon clearing Tuesday night through Thursday. The 
shortwave trough passing through Thursday night should break things up a 
bit. 


It will be cooler Friday behind departing trough...especially in the 
mountains. After trough moves out...models pretty much agree on 
rebuilding a strong longwave ridge along 130w into next week. This 
again brings much above average temperatures to the region...except the 
valley where night and morning clouds/fog will hold temperatures down. 
Forecast problem for the valley will be where the inversion sets up. A 
shallow inversion would bring more widespread fog...while a deeper 
inversion would mean a persistent low cloud deck with little fog. 


&& 


Aviation...MVFR with local IFR conditions will continue overnight 
due to a developing stratus deck just above 1000 feet above ground level along with 
haze and mist. This stratus deck with also cause mountain 
obscuration to exist over the foothills of the southern Sierra 
Nevada and lower Tehachapi Mountains. This stratus deck over the San 
Joaquin Valley may lower to below 1000 feet above ground level overnight before 
lifting slightly on Tuesday. Elsewhere...VFR conditions will prevail 
across the central California interior through 06z Wednesday. 


&& 


Air quality issues... 
on Tuesday January 6 2009... unhealthy for sensitive groups in 
Fresno County. Fireplace/wood stove burning is prohibited in 
Fresno and Madera counties. 
Further information is available at valleyair.Org 


&& 


Hnx watches/warnings/advisories... 
none. 
&& 


$$ 


Public...dch 
AVN/fw...Molina 


Weather.Gov/Hanford