Area Forecast Discussion
Issued by NWS Los Angeles, CA

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FXUS66 KLOX 251815
AFDLOX

SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
1100 AM PDT FRI JUL 25 2014

...AVIATION DISCUSSION UPDATED...

.SYNOPSIS...
HIGH PRESSURE WILL REMAIN ANCHORED OVER THE DESERT SOUTHWEST THROUGH
THE MIDDLE OF NEXT WEEK. THIS WILL RESULT IN CONTINUED WARM
TEMPERATURES ACROSS THE AREA. SOUTHERLY FLOW AROUND THE HIGH
PRESSURE WILL BRING IN SOME HIGH CLOUDS THIS WEEKEND...AND THE
SLIGHT POSSIBILITY OF SOME SHOWERS OR THUNDERSTORMS OVER THE LOS
ANGELES MOUNTAINS BY SUNDAY. OTHERWISE...SOME NIGHT AND MORNING
STRATUS AND FOG CAN BE EXPECTED ACROSS THE COASTAL PLAIN.

&&

.SHORT TERM (REST OF TODAY-SUN)...MAIN FORECAST ISSUE TODAY WILL BE
TO MONITOR THE DEVELOPMENT AND MOVEMENT OF THE ISOLATED SHOWERS AND
THUNDERSTORMS THAT POPPED UP EARLY THIS MORNING TO OUR SOUTH. AREA
HAS MOVED UP FROM MEXICO AS IT WRAPS AROUND THE LARGE UPPER HIGH
CENTERED OVER WEST TEXAS. LIGHTNING STRIKES BEING DETECTED ALONG THE
CLOUD BAND FROM EAST OF US IN SAN BERNARDINO COUNTY...ALL THE WAY
SOUTH OF US OVER THE COASTAL SOUTHWEST OF SAN DIEGO. THESE TRW`S
HAVE FORMED RIGHT ALONG AN INSTABILITY GRADIENT THAT RUNS FROM SAN
DIEGO NORTH TO VEGAS. THAT LINE ALSO REPRESENTS THE DEMARCATION
BETWEEN THE HIGHER 850 MB DEWPOINTS TO ITS EAST AND LOWER TO ITS
WEST...INCLUDING OVER OUR AREA. MODELS KEEP THE MORE FAVORABLE
CONVECTIVE CONDITIONS FAR ENOUGH TO OUR EAST TODAY AND TONIGHT...SO
FOR THE TIME BEING DO NOT EXPECT THIS AREA TO MOVE INTO LA OR VTU
COUNTY. THE NAM DOES FORECAST A POCKET OF INSTABILITY OVER THE
VENTURA COUNTY MOUNTAINS THIS AFTERNOON...SO MAY BE GET SOME
CLOUD BUILDUPS THERE...BUT THAT`S ABOUT IT. THE VERY HIGH
RESOLUTIONS MODELS...SUCH AS THE RAPID REFRESH AND OUR LOCAL WRF
MODEL...ALSO KEEP OUR AREA PRECIP-FREE TODAY.

OTHERWISE...WITH AN INCREASE IN ONSHORE PRESSURE
GRADIENTS...TEMPERATURES HAVE COOLED TODAY COMPARED TO YESTERDAY AT
THIS TIME...AND AS EXPECTED. SO EVEN THOUGH HIGH TEMPS TODAY WILL BE
ABOVE NORMAL...THE TRIPLE DIGIT HIGHS SHOULD BE CONFINED TO THE
ANTELOPE VALLEY. SOME VALLEY LOCATIONS WILL FLIRT WITH THE CENTURY
MARK...BUT ARE EXPECTED TO BE BELOW.

MARINE LAYER STRATUS ALSO RETURNED TO THE LA BASIN AND THE BEACHES
OF VTU COUNTY THIS MORNING. EDDY IS JUST AS STRONG TOMORROW SO
EXPECT A REPEAT OCCURRENCE TONIGHT AND SUNDAY.

TEMPERATURES SATURDAY AND SUNDAY WILL BE VERY SIMILAR TO TODAY`S.
AGAIN...ANY READINGS OVER 100 WILL BE CONFINED TO THE AV.

***FROM PREVIOUS DISCUSSION***

.LONG TERM (MON-THU)...FOR THE EXTENDED...MODELS REMAIN ON THE SAME
SYNOPTIC PAGE...BUT DIFFER IN SOME DETAILS. AT UPPER LEVELS...RIDGE
WILL REMAIN DOMINANT FEATURE OVER THE SOUTHWEST. THE GFS KEEPS THE
RIDGE CENTERED OVER NEW MEXICO WHILE THE ECMWF ACTUALLY CENTERS THE
RIDGE OVER THE CALIFORNIA/ARIZONA BORDER. NEAR THE SURFACE...WEAK TO
MODERATE ONSHORE FLOW WILL PREVAIL.

FORECAST-WISE...NOTHING TOO EXCITING EXPECTED THROUGH THE PERIOD. NO
MATTER WHICH MODEL VERIFIES WITH REGARD TO THE PLACEMENT OF THE
UPPER RIDGE...THE AMOUNT OF MID-LEVEL CLOUDS/MOISTURE SHOULD
DECREASE THROUGH THE PERIOD. SO...NO SIGNIFICANT CHANCES OF ANY
CONVECTIVE PRECIP THROUGH THE PERIOD...AND A GENERAL MOSTLY CLEAR
SKY CONDITION (OUTSIDE OF THE MARINE LAYER STRATUS). WITH REGARD TO
THE STRATUS...WILL EXPECT STRATUS/FOG TO CONTINUE TO IMPACT THE
COASTAL PLAIN EACH NIGHT/MORNING WITH MINOR DAY-TO-DAY CHANGES IN
AREAL COVERAGE. AS FOR TEMPERATURES...ONLY MINOR CHANGES ARE
EXPECTED FROM DAY TO DAY...WITH MOST AREAS REMAINING AT OR SLIGHTLY
ABOVE SEASONAL NORMALS.

&&

.AVIATION...25/18Z...
MODERATE TO HIGH CONFIDENCE IN THE 18Z TAFS.  SLOW CLEARING IN SOME
COASTAL LOCATIONS THOUGH VFR CONDITIONS ARE IN PLACE THROUGHOUT THE
SERVICE AREA.  THE MARINE LAYER IS EXPECTED TO RETURN TO ALL COASTAL
SITES OVERNIGHT IN A SIMILAR PATTERN AS THIS MORNING THOUGH FOR A
SLIGHTLY LONGER DURATION.  OTHERWISE AND ELSEWHERE VFR CONDITIONS
ARE EXPECTED.

KLAX...MODERATE CONFIDENCE IN THE 18Z TAF.  THE MARINE LAYER IS
EXPECTED TO RETURN OVERNIGHT IN A SIMILAR PATTERN AS THIS MORNING
THOUGH FOR A SLIGHTLY LONGER DURATION.  THERE IS A 20 PERCENT CHANCE
THAT CIGS WILL SLIP INTO THE IFR CATEGORY FOR ONE TO THREE HOURS
THROUGH 16Z... A 10 TO 20 PERCENT CHANCE THAT CIGS WILL LINGER UNTIL
AS LATE AS 19Z... AND A 20 PERCENT CHANCE THAT EAST WINDS WILL REACH
OR EXCEED 9 KNOTS BETWEEN 13Z AND 16Z.  OTHERWISE VFR CONDITIONS ARE
EXPECTED.

KBUR...HIGH CONFIDENCE IN THE 18Z TAF. VFR CONDITIONS EXPECTED
THROUGHOUT THE FORECAST PERIOD.

&&

.MARINE...25/900 AM...

HIGH CONFIDENCE IN CURRENT FORECAST.  WINDS AND SEAS ARE CONTINUING
TO DECREASE THOUGH IT WILL BE A FEW MORE HOURS UNTIL SEAS ARE
BELOW ADVISORY CRITERIA. THEREFORE THE SMALL CRAFT ADVISORY WAS
CHANGED TO HAZARDOUS SEAS ONLY AND EXTENDED THROUGH 3 PM.  BEYOND
THIS AFTERNOON... CONDITIONS ARE EXPECTED TO REMAIN BELOW ADVISORY
CRITERIA THROUGH THE REMAINDER OR THE FORECAST PERIOD.

REPORTS OF MOSTLY DRY LIGHTNING TO THE SOUTH OF THE FORECAST AREA
THIS MORNING.  THUNDERSTORMS ARE EXPECTED TO REMAIN TO THE SOUTH
THROUGH THE FORECAST PERIOD BUT WILL COME NEAR THE SOUTHERN BORDER
OF ZONES 676 AND 655 THIS AFTERNOON THROUGH SUNDAY.

&&

.FIRE WEATHER...25/220 AM...
ELEVATED FIRE DANGER ACROSS INTERIOR SECTIONS OF FORECAST AREA THIS
AFTERNOON AND EVENING DUE TO COMBINATION OF GUSTY ONSHORE
WINDS...VERY WARM TEMPERATURES...AND LOW HUMIDITIES. ONSHORE WINDS
GUSTING BETWEEN 25 AND 35 MPH WILL BE COMMON ACROSS THE INTERIOR
VALLEYS...MOUNTAINS...AND DESERTS...WITH LOCAL GUSTS AS HIGH AS 45
MPH ACROSS THE FAVORED FOOTHILLS OF THE ANTELOPE VALLEY.
MEANWHILE...MANY OF THESE SAME AREAS WILL SEE HUMIDITIES FALLING
INTO THE TEENS DURING THE AFTERNOON HOURS...WITH ISOLATED SINGLE
DIGIT READINGS IN THE MOUNTAINS AND ANTELOPE VALLEY. WHILE BRIEF
CRITICAL FIRE WEATHER CONDITIONS WILL BE POSSIBLE IN THE MOUNTAINS
AND ANTELOPE VALLEY TODAY...THERE WILL NOT BE A SUFFICIENTLY
LONG DURATION TO WARRANT A RED FLAG WARNING.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS (SEE LAXMWWLOX).

&
$$

PUBLIC...JACKSON/RAT
AVIATION...KJ
MARINE...KJ
FIRE WEATHER...GOMBERG/RAT
SYNOPSIS...RAT

WWW.WEATHER.GOV/LOSANGELES





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