000 
fxus66 klox 201029 
afdlox 


Area forecast discussion 
National Weather Service Los Angeles/Oxnard California 
329 am PDT Fri Jul 20 2018 


Synopsis...19/817 PM. 


Temperatures will remain hot across the region for at least another 
week with excessive heat in many areas Tuesday through Thursday. 
Overnight and morning low clouds will bring some relief along the 
coast. There is a slight chance of thunderstorms across the region 
Friday and in the Ventura County mountains on Saturday afternoon. 


&& 


Short term (tdy-sun)...20/303 am. 


The marine layer depth is 1100 feet deep. Onshore grads are about 
3 mb onshore and there is no eddy. The stratus deck is slowly 
filling in and will cover most of the immediate coastal area by 
sunrise. Not much change in todays weather from yesterdays. The 
same 596 dm is off to the east with 591dm hgts over California. The 
convective parameters are similar to ydys with decent moisture and 
instability but like ydy there is really no kicker in sight. So 
20 percent pops (but not higher) for the mtns...Antelope Vly and 
the slo/Kern County line looks good. Max temps will be right at 
normals. 


Not much change at all for the weather on Saturday. The upper 
level flow is more southerly and drier which will cut off the thunderstorm 
threat. The marine layer may be a little better developed which 
might lead to a degree or two drop in the beach temps. 


The upper level high begins to move to the west on Sunday. Hgts 
bump up to 594 dm and sfc gradients relax. These two things will 
bring 3 to 6 degrees of warming to the area and most areas will be 
2 to 4 degrees above normal. There is no monsoon flow and this 
will keep convection at Bay. 


A good northwest to southeast pressure gradient sets up over sba County Sunday 
evening. This will trigger a sundowner with the strongest winds 
focused on areas west of Goleta. 


Long term (mon-thu)...20/329 am. 


The entirety of next week will be all about the heat. 


The large upper high move to the west and strengthens. It will be 
centered over the Arizona/nm border Mon afternoon then right over Arizona 
by Tuesday afternoon. On Wednesday the high will be over the 
California/NV/AZ intersection with a 600 dm central hgt. Hgts rise from 
595 dm Monday to 596 dm then to 598 dm on Wednesday and then fall 
about a single dm Thu. Max temps will rise every day Monday 
through Wednesday and will likely remain the same on Thursday. On 
Wednesday and Thursday Max temps will be 10 to 15 degrees above 
normal. 


Current low temps seem a little low in some places during this 
event and there will likely be some upward trends as the event 
draws nearer and the gradients and inversions come into closer 
focus. 


The combination of above normal daytime highs and very warm 
overnight lows will produce a dangerous heat event. An excessive 
heat watch is in effect now for most of the area from Tuesday thru 
Thursday. 


A decent north to south gradient sets up on Monday night. There 
will be sundowner winds each night as well as the I-5 corridor. 
These winds will minimize the marine layer south of pt Conception. 
The current forecast gradients are a little less than they were 
ydy and would only result in winds that are just below advisory 
levels. Still anywhere there are northerly downsloping winds there 
will be much warmer overnight lows. 


&& 


Aviation...20/0641z. 


At 0550z at klax, the marine layer was around 1200 ft deep. The 
top of the inversion was around 2700 feet with a temperature of 
23c. 


Low confidence in coastal tafs through 18z with respect to cig 
timing and cloud base hgts. Cig hgts could be off by 1 flgt Cat 
and timing could be off by up to 2 hours. Good confidence after 
18z 


Good confidence in tafs. 


Klax...low confidence in taf through 18z. Cigs may arrive any time 
between 09z and 13z. There is a 30 percent chc that cigs will be 
ovc012. Cigs could clear by 16z. There is a 10 percent chc of no 
cigs at all. Good confidence that there will be no east wind 
component over 4 kt. Good confidence in taf aft 18z. 


Kbur...high confidence in the ceiling and visibility unlimited taf. 


&& 


Marine...20/207 am. 


Small Craft Advisory (sca) winds are not forecast across the 
coastal waters thru Sun morning. Small Craft Advisory conds are expected across 
the southern two outer waters zones (pzz673/pzz676) Sun afternoon 
thru Mon. There is a 30%-40% chance of Small Craft Advisory level winds across the 
northern outer waters zone (pzz670) Sun afternoon thru Sun night, 
then Small Craft Advisory conds are expected Mon. 


Across the inner waters, Small Craft Advisory conds are not expected through sun. 
However, there is a 40% chance of Small Craft Advisory conds across the northern 
inner waters and western portions of the sba channel Sunday. 


Choppy short-period seas will persist across much of the waters 
through the weekend. 


&& 


Lox watches/warnings/advisories... 
California...excessive heat watch in effect from Tuesday morning through 
Wednesday afternoon for zones 34>38-51. (See laxnpwlox). 
Excessive heat watch in effect from Monday morning through 
Thursday evening for zones 39>41-44>46-52>54-59-88-547. (See laxnpwlox). 
Pz...none. 


&& 


Hazard potential outlook (sun-thu). 


An extended heat wave is expected Sunday through at least Thursday 
of next week, especially for inland areas. Heat advisories and/or 
warnings will be likely. Elevated fire weather conditions due to 
the extended period of hot and dry conditions, especially southern 
Santa Barbara County where gusty sundowner winds will add to the 
threat. A long period southerly swell will also bring elevated 
surf and strong rip current potential early next week across south 
facing beaches coinciding with the heat wave. 


&& 


$$ 


Public...rorke 
aviation...rorke 



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