Southwest California area forecast discussion 
National Weather Service Los Angeles/Oxnard California 
1036 am PDT Friday may 24 2013 


Synopsis... 
may gray is the story for the Holiday weekend...but with decent 
afternoon clearing. Gusty northwesterly winds will develop as a weak 
cold front moves through the area with showers possible Tuesday. 
Afternoon temperatures will remain below normal through next 
Tuesday...then warming to seasonal normals by midweek. 


&& 


Short term (today-sunday)... 
morning soundings show some warming above 1000 feet...which should 
result in a noticeable warm up in the inland valleys and mountains. 
Coastal sections and valleys should also see a couple of degrees of 
warming from yesterday...but with a still deep marine layer...our 
current forecasted warming trend may be a little too much. 
Otherwise...forecast in good shape...and sent out just a minor 
update to reflect current sky/weather scenario. The main challenge for 
today will be to figure out how and when the marine layer will 
return back to normal depths...and what rain chances we have for 
early next week. 


***From previous discussion*** 


A broad trough of low pressure continues to linger along the West 
Coast this morning. Onshore flow firmly in place will continue to 
strengthen over the Holiday weekend as a series of weak cold 
fronts approach the area. Strong onshore surface pressure 
gradients will likely develop through Saturday...keeping may gray 
tidings true. Low clouds and fog will likely sock in the beaches 
over the weekend. A weak cold front washing out over the area on 
Sunday may permit a little more clearing on Sunday afternoon for 
the Santa Barbara South Coast and Ventura County beaches...but 
another weak frontal boundary will re-enforce the onshore flow 
for Monday. 


With the weak boundary washing out over the area on Sunday...a 
moderate sundowner and Interstate 5 corridor wind event could 
develop between Sunday afternoon and Monday morning. While still 
early...an advisory level wind event could develop across the 
South Coast of Santa Barbara County...through the Santa Ynez 
range...and through Interstate 5 corridor Sunday. 


Strong onshore gradients between klax-kdag and ksmx-kbfl may 
permit for possible advisory level winds out in the Antelope 
Valley through the Soledad Canyon from Saturday through at least 
Sunday. Breezy conditions will also be prevalent across the 
interior valleys including areas such as Paso Robles and the 
Carrizo Plain. 


Long term (memorial day-thursday)... 


Another cold front approaching the region will strengthen onshore 
surface pressure gradients on Memorial Day. Gale force winds 
developing across the coastal waters will likely spill over into 
the coastal sections. Gusty winds could develop for most areas north 
of Point Conception...through the Soledad Pass and into the 
Antelope Valley...and allow for a stronger sundowner wind event 
on Monday afternoon and night. Elsewhere...very little 
clearing...if any...will occur on Memorial Day with valley areas 
likely struggling to clear as a deep marine layer and strong 
onshore flow keeping a persistent marine influence and stratus 
deck in place. 


Probability of precipitation have been increased slightly as the front rolls through 
between Monday night and Tuesday night. Due to the northwest low- 
level flow...the best chance for any rainfall will occur for areas 
north of Point Conception and along the northern slopes of the 
mountains. With mixing ratio near 8 g/kg with the front...enough 
moisture is present to possibly allow for some showers south of 
Point Conception. Showers or measurable drizzle from the night 
through morning marine layer stratus deck are plausible with the 
pattern. 


A warming trend should occur for the latter half of next week as 
high pressure aloft builds into the West Coast. Sundowner winds and 
northerly winds through the Interstate 5 corridor are still 
possible into Thursday or Friday as the northerly surface gradient 
remains in place. 


&& 


Aviation...24/1800z. 


Middle/upper level trough of low pressure upstream will persist. Upper 
level moderate southwest winds will become strong southwest after 
25/20z while middle level light and variable winds become light 
northwest after 25/08z. Increasing upper level moisture between 
25/00-25/12z. Moderate onshore pressure gradient through 25/02z and 
after 25/19z otherise weak onshore gradient. Low level cloud tops 
varied from 4.2kft over the basin to 1kft or less along the central 
coast this morning. Clouds will differ by plus .5kft along the 
central coast to minus 1.5kft over the basin Saturday morning. 


Klax...ceilings 035 becoming scattered after 24/20z then chance ceilings 013 
between 25/08-25/17z then chance ceilings 022 between 25/17-25/20z. 


Kbur...chance ceilings 020 after 25/09z. 


Virtually certain - 95-100% 
very likely - 80-95% 
likely - 60-80% 
chance - 30-60% 
very unlikely - 20% or less 


&& 


Lox watches/warnings/advisories... 
Small Craft Advisory (see laxmwwlox). 
High rip current risk (see laxsrflox). 


&& 


$$ 


Public...rk/Hall 
synopsis...Dumas 


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