Weather Service Report


492 
FXUS66 KLOX 261705
AFDLOX

SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
900 AM PST MON JAN 26 2015

.SYNOPSIS...
A COUPLE OF LOW PRESSURE SYSTEMS WILL IMPACT THE AREA THIS WEEK. THE 
FIRST WILL LIKELY BRING SHOWERS THROUGH EARLY TUESDAY. THE NEXT 
COULD BRING A SMALL CHANCE OF RAIN THURSDAY OR FRIDAY. TEMPERATURES 
WILL REMAIN NEXT NORMAL THROUGH THE WEEK.

&&

.SHORT TERM (TODAY-WED)...
THE LOW PRESSURE SYSTEM THAT WILL IMPACT US THROUGH TUESDAY REMAINS 
450 MILES SOUTHWEST OF LOS ANGELES. SOUTHEAST FLOW HAS SETTLED INTO 
THE AREA...BRINGING A WARM AIRMASS UP FROM THE SOUTH. WHILE MAXIMUM 
TEMPERATES WILL BE MUCH LOWER THAN YESTERDAY...THEY WILL BE A FEW 
DEGREES WARMER THAN PREVIOUSLY EXPECTED DUE TO THE LOCALIZED 
OFFSHORE FLOW AND WARM START TO THE MORNING. UPDATED FORECAST 
ACCORDINGLY. WHILE NO MEASURABLE RAIN IS EXPECTED THIS 
MORNING...ADDED A SLIGHT CHANCE TO LOS ANGELES COUNTIES WITH A FEW 
REPORTS OF LIGHT BIG DROP RAIN. RAIN CHANCES FOR LATE THIS AFTERNOON 
AND NIGHT LOOK UNCHANGED FROM PREVIOUS FORECAST. WISH WE COULD BE 
MORE DEFINITIVE WITH THE POPS...BUT UNCERTAINTY REMAINS AS TO THE 
COVERAGE OF MEASURABLE RAIN. THIS IS DUE TO THE FLOW LOOKING MORE 
EASTERLY THAN SOUTHEASTERLY WHICH WOULD PRODUCE A DRYING EFFECT AT 
LOWER LEVELS. REGARDLESS...ANY RAINFALL STILL LOOKS LIGHT. THE 
MOISTURE ALSO LOOKS TO EXIT THE AREA A LITTLE QUICKER...SO TUESDAY 
MORNING POPS MAY NEED TO BE TRIMMED BACK WITH THE AFTERNOON PACKAGE.

***FROM PREVIOUS DISCUSSION***

563 DM UPPER LOW 400 MILES SOUTH WEST OF L.A. THIS LOW WILL SLOWLY 
MAKE ITS WAY TO THE NNE AND WILL BE OVER PT CONCEPTION AROUND DAWN 
TUESDAY. AS THIS LOW MOVES TOWARDS THE REGION IT WILL ENTRAIN A 
LARGE MASS OF MOISTURE OVER SE CA AND AZ AND ADVECT THIS MOISTURE 
INTO SRN CA. THIS FLOW TRAJECTORY WILL ACTUALLY FAVOR RAIN CHANCES 
FOR THE L.A. MTNS AND THE ANTELOPE VLY. THIS MORNING WILL BE MOSTLY 
CLOUDY AND THERE WILL BE A BIG DROP SPRINKLE OR TWO HERE AND THERE 
AS SOME PRECIP FALLS FROM THE MID LEVEL DECKS BUT NOTHING OF NOTE OR 
OVER A HUNDREDTH OF AN INCH. THERE WILL BE ENOUGH MOISTURE OVER THE 
AREA MIXED WITH A LITTLE PVA TO BRING A CHC OF LIGHT RAIN SHOWERS TO 
MOST OF L.A. COUNTY AND A SLIGHT CHC TO VTA COUNTY. THE BEST CHC OF 
RAIN WILL BE THIS EVENING. THE UPPER LOW WILL BE 100 MILES SOUTHWEST 
OF PT CONCEPTION MAXIMUM MOISTURE WILL BE OVER THE AREA AND A VORT 
MAX WILL ROTATE OVER THE FORECAST AREA FROM THE SOUTH TO THE NORTH. 
RAIN WILL BE LIKELY FOR L.A. COUNTY AND MOST OF THE MTNS. DUE TO THE 
SE TO NW MOVEMENT OF THE VORT MAX THERE WILL ONLY BE CHC OF RAIN 
OVER THE WATERS AND THE VLYS AND COASTAL SECTIONS OF VTA COUNTY. 
THERE WILL ONLY BE A SLIGHT CHC OF RAIN OVER THE CENTRAL COAST. THE 
CHC OF PRECIP WILL DIMINISH AFTER MIDNIGHT AS THE VORT LOBE MOVES 
OFF. BY TUESDAY MORNING THE CHC OF RAIN WILL BE CONFINED TO AREAS 
NORTH OF PT CONCEPTION...ALL OF THE MTNS AND THE ANTELOPE VLY. BY 
TUESDAY AFTERNOON THERE WILL ONLY BE A SLIGHT CHC OF SHOWERS NEAR 
THE KERN COUNTY BORDER. SNOW LEVELS WILL BE RATHER HIGH...AROUND 
7000 FEET. THE SKI RESORTS COULD SEE AN INCH OR TWO OF NEW SNOW. 

RAINFALL AMOUNTS WILL LIKELY BE THE HIGHEST IN THE ANTELOPE VALLEY 
AND THE NORTH FACING SLOPES OF THE SAN GABRIEL MOUNTAINS...WHERE 
0.25-0.50" OF RAIN ARE POSSIBLE. AREAS WEST OF THE MOUNTAINS WILL 
GENERALLY RECEIVE 0.10-0.25" OR LESS...BUT AMOUNTS WILL BE HIGHLY 
VARIABLE. RAINFALL RATES SHOULD REMAIN BELOW ABOUT 0.15" PER HOUR.

WHILE THUNDER IS NOT MENTIONED IN THE FORECAST THE CHC OF A TSTM IS 
NOT ZERO. THE AREA NEAR THE LOW CENTER WILL NEED MONITORING. 

A LITTLE POP UP RIDGE (AHEAD OF ANOTHER UPPER LOW TO THE SW) IS 
SLATED FOR WEDNESDAY. SKIES WILL TURN PARTLY CLOUDY. RISING HGTS AND 
WEAK OFFSHORE FLOW WILL ALLOW FOR NICE BUMP UP IN TEMPS.

.LONG TERM (THU-SUN)...
ANOTHER UPPER LOW TO OUR SW PUSHES THE RIDGE OUT AS IT MOVES TOWARDS 
SRN CA. THIS LOW IS MUCH WEAKER THAN TODAYS AND WILL LIKELY OPEN UP 
INTO A TROF AS IT MOVES OVERHEAD. ONLY THE EC SEES THIS TROF 
PRODUCING ANY RAINFALL AND EVEN THEN JUST OVER THE L.A./VTA MTNS AND 
THE AV. DURING THIS TIME SKIES WILL BE PARTLY OR MOSTLY CLOUDY AND 
MAX TEMPS WILL BE PRETTY CLOSE TO NORMAL PERHAPS A DEGREE OR TWO 
WARMER DUE TO THE OFFSHORE FLOW TO THE LOW OFF THE COAST.

BOTH THE EC AND THE GFS AGREE THAT ANOTHER RIDGE IS ON TAP FOR NEXT 
WEEKEND. SKIES SHOULD CLEAR AND MAX TEMPS WILL RISE SEVERAL DEGREES 
ABOVE NORMALS WITH THE HIGHER HEIGHTS AND WEAK OFFSHORE FLOW.

&&

.AVIATION...26/12Z...

AT 0920Z AT KLAX... THE INVERSION EXTENDS FROM THE SURFACE UP TO 
1000 FEET WITH A TEMPERATURE OF 23 DEGREES C AT THE TOP. 

OVERALL...MODERATE CONFIDENCE IN 12Z TAFS.  REDUCED CONFIDENCE DUE 
TO UNCERTAINTY IN THE TIMING AND INTENSITY OF THE INCOMING 
PRECIPITATION AND THE EFFECT ON WIND FLOW AND VSBY.  AN INCREASING 
CHANCE OF PRECIPITATION ACROSS THE REGION BEGINNING IN LOS ANGELES 
COUNTY 22Z-00Z AND MOVING NORTH TOWARD SAN LUIS OBISPO COUNTY BY 
06Z.  CONDITIONS ARE MOST LIKELY TO REMAIN VFR THROUGH THE FORECAST 
PERIOD THOUGH THERE IS A THIRTY PERCENT CHANCE OF MVFR CONDITIONS 
AFTER 23Z.  

KLAX...MODERATE CONFIDENCE IN 12Z TAF.  REDUCED CONFIDENCE DUE TO 
UNCERTAINTY IN THE TIMING AND INTENSITY OF THE INCOMING 
PRECIPITATION AND THE EFFECT ON WIND FLOW AND VSBY.  AN INCREASING 
CHANCE OF PRECIPITATION BEGINNING 22Z-00Z.  CONDITIONS ARE MOST 
LIKELY TO REMAIN VFR THROUGH THE FORECAST PERIOD THOUGH THERE IS A 
THIRTY PERCENT CHANCE OF MVFR CONDITIONS AFTER 23Z.  A TWENTY 
PERCENT CHANCE OF EAST TO SOUTHEAST WINDS GREATER THAN 7 KTS PRIOR 
TO 19Z.

KBUR...MODERATE CONFIDENCE IN 12Z TAF.  REDUCED CONFIDENCE DUE TO 
UNCERTAINTY IN THE TIMING AND INTENSITY OF THE INCOMING 
PRECIPITATION AND THE EFFECT ON WIND FLOW AND VSBY.  AN INCREASING 
CHANCE OF PRECIPITATION BEGINNING 22Z-00Z.  CONDITIONS ARE MOST 
LIKELY TO REMAIN VFR THROUGH THE FORECAST PERIOD THOUGH THERE IS A 
THIRTY PERCENT CHANCE OF MVFR CONDITIONS AFTER 23Z.

&&

.MARINE...26/300 AM...

AN AREA OF LOW PRESSURE WILL MOVE NORTH OVER THE REGION TODAY... 
BRINGING A CHANCE OF PRECIPITATION AND SHIFTING THE WINDS TO THE 
SOUTHEAST.  LOCALLY GUSTY WINDS TO 25 KT ARE POSSIBLE INTO THE 
EVENING HOURS.  NORTH WINDS WILL RETURN ON WEDNESDAY.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
HIGH RIP CURRENT RISK (SEE LAXSRFLOX).

&&
$$

PUBLIC...KITTELL/RORKE
AVIATION...KJ
MARINE...KJ
SYNOPSIS...SETO

WWW.WEATHER.GOV/LOSANGELES



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