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Next 12 Hours

Forecast data from the National Digital Forecast Database.

5 Day Forecast

• Monday
• 
• High: 61 °
• Low: 43 °
• Chance of Rain

• Tuesday
• 
• High: 61 °
• Low: 43 °
• Partly Cloudy

• Wednesday
• 
• High: 61 °
• Low: 40 °
• Chance of Rain

• Thursday
• 
• High: 65 °
• Low: 40 °
• Partly Cloudy

• Friday
• 
• High: 65 °
• Low: 43 °
• Clear

Southwest California area forecast discussion 
National Weather Service Los Angeles/Oxnard California 
950 PM PST sun Feb 12 2012 


New aviation discussion 


Synopsis... 


Two low pressure systems will affect the area through middle 
week...bringing another threat of showers mainly on Monday...and 
again Wednesday. It will be breezy at times along with cool 
temperatures. Drier and warmer conditions are expected for later in 
the week...with another chance of showers by Sunday. 


&& 


Short term (tonight-wed)...a rather cool day across the forecast 
region as expected with some residual low level moisture lingering 
across much of Los Angeles County and less widespread over the rest 
of the region. High temperatures were mainly in the lower to middle 60s...with 
cooler temperatures across the interior areas. 


Low level moisture will continue to linger overnight with partly 
cloudy skies across much of the region this evening. Clouds will be 
on the increase overnight as a weak cold front moves into the 
central coast overnight with a few light showers expected. Clouds 
will also be on the increase west of the mountains S of Point 
Conception with a deepening marine layer and some low atmospheric 
lift to help squeeze out some drizzle or light showers by Monday 
morning. Rainfall accumulations north of Point Conception should remain 
quite light...likely around a tenth of an inch...with a few 
locations receiving near a quarter inch. Expecting less than a tenth 
of an inch for areas S of Point Conception with this weak frontal 
passage...except for the foothills and mountains of la County as 
decent SW cyclonic flow ahead of the front should help slightly 
enhance amounts of precipitation in the San Gabriel Mountains. Temperatures will 
remain quite cool with snow levels initially around 5000 to 5500 feet 
during the day. 


By late tomorrow afternoon and evening.. a cold upper level low will 
drop south over interior California bringing a fairly strong 
vorticity maximum over the forecast area Monday afternoon into the overnight 
hours. The dynamics from this feature and 500 mb temperatures forecast to 
be around -28 degrees celsius could spark a few thunderstorms across 
the interior areas including the Ventura and Los Angeles County 
mountains as well as the Antelope Valley. Brief heavy downpours and 
small hail could affect these areas as well. Snow levels will drop 
rapidly to around 3000 to 3500 feet Monday evening with strong gusty 
northerly winds affecting driving conditions across the Interstate 5 
corridor. A Winter Weather Advisory was issued and valid for noon 
tomorrow through early Tuesday morning for the potential of 
hazardous driving conditions. Snow accumulation will remain 
light...generally between 2 to 4 inches due the lack of moisture to 
tap into with this system. By Tuesday...there will continue to be 
plenty of low clouds banked up against the northern slopes of the 
Los Angeles and Ventura County mountains. The highest snow 
accumulations will occur along the northern slopes. 


As far as winds...strong gusty west to northwest winds will develop 
behind the front by tomorrow afternoon affecting the central coast 
as well as all immediate coastal areas...mountains and Antelope 
Valley. Wind advisories have already been issued valid for tomorrow 
afternoon through evening hours in most areas...and into early 
Tuesday morning for some interior locations. Winds will diminish 
some on Tuesday. Conditions are expected to generally dry out on 
Tuesday...except a few lingering snow showers on north facing slopes. 


The latest 00z NAM-WRF is now indicating the secondary upper low to 
remain well east of the region on Wednesday now. However...the 00z 
GFS continues to show a very cold upper low parked over Southern 
California on Wednesday. If the European continues this trend...then 
the NAM-WRF would be the outlier. Therefore...the previous 
discussion seems reasonable to leave alone. 


..from previous discussion... 


The 12z GFS and European model (ecmwf) solutions coming into better agreement on 
Wednesday forecast...with both models dropping another cold low 
pressure system right over Southern California. Based on this 
trend...bumped up probability of precipitation and lowered snow levels accordingly. 
Again...this system will likely have limited moisture...but could 
have some very cold air aloft and dynamics. With this in 
mind...could see locally heavy showers and can not rule out the 
possibility of thunderstorms if the cold pool aloft tracks right 
over the forecast area. 


Long term (thu-sun)... 
drying and warming trend is expected Thursday into Saturday. There is 
the potential for some gusty offshore winds Wednesday night through 
Friday. By Sunday...there is the potential for another cold low 
pressure system to drop down across Southern California...bringing 
yet another threat of showers and low snow levels. 


&& 


Aviation... 


13/0550z... 


A weak front will move over the central coast overnight and south of 
Point Conception after daybreak Monday. This system will not produce 
much rain especially south of Point Conception. It will bring gusty 
northwest winds to the area later Monday morning through the 
evening. There will also be a slight chance of thunderstorms over the mountains and 
deserts during the afternoon and evening. Low confidence in tafs as 
ceilings will vary considerably through early Monday afternoon. 


Klax...ceilings will vary frequently between 015 and 040 after 12z. 
There is a 30 percent chance of a shower from 12z-20z. Good 
confidence in breezy VFR forecast after 21z. 


Kbur...ceilings will vary frequently between 015 and 040 after 12z. 
There is a 30 percent chance of a shower from 12z-20z. 


&& 


Lox watches/warnings/advisories... 
Gale Warning (see laxmwwlox). 
Small Craft Advisory (see laxmwwlox). 
Wind Advisory (see laxnpwlox). 
Winter Weather Advisory (see laxwswlox). 
High surf advisory (see laxcfwlox). 
High rip current risk (see laxsrflox). 


&& 


$$ 


Public...Kaplan/gomberg 
aviation...asr 
synopsis...cs 


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