Area Forecast Discussion
Issued by NWS San Diego, CA

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000
FXUS66 KSGX 302048
AFDSGX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
148 PM PDT TUE SEP 30 2014

.SYNOPSIS...
WEAK ONSHORE FLOW AND NORTHWEST FLOW ALOFT WILL CONTINUE INTO EARLY
WEDNESDAY...BRINGING PATCHY NIGHT AND MORNING STRATUS FOR THE COAST
AND WESTERN VALLEYS...AND SOME ADDITIONAL WARMING. FOR THURSDAY INTO
SATURDAY...HIGH PRESSURE RIDGE BUILDING ALOFT AND WEAK TO LOCALLY
GUSTY OFFSHORE FLOW WILL BRING INCREASINGLY HOTTER AND DRIER
DAYS...WITH DAY-TIME HIGHS REACHING 10 TO 20 DEGREES ABOVE NORMAL
FRIDAY AND SATURDAY FOR INLAND AREAS. SOME STRATUS AND FOG POSSIBLE
ALONG THE COAST WEDNESDAY NIGHT INTO THURSDAY MORNING BEFORE THE
OFFSHORE FLOW ERADICATES THE MARINE LAYER. STILL QUITE HOT ON
SUNDAY...EXCEPT SOME SLOW COOLING ALONG THE COAST. GRADUALLY COOLING
TO CONTINUE INTO EARLY NEXT WEEK AS THE RIDGE WEAKENS...BUT DAY-TIME
HIGHS WILL STILL BE ABOVE NORMAL.

&&

.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...

AFTERNOON VISIBLE SATELLITE SHOWS CLEAR SKIES ACROSS THE FORECAST
AREA. LOCAL WRF CONTINUES TO SHOW A WEAK COASTAL EDDY SPINNING UP
TONIGHT...AND THIS SHOULD BRING BETTER STRATUS COVERAGE TONIGHT INTO
TOMORROW MORNING ALONG THE COAST AND WESTERN VALLEYS...WITH A MARINE
LAYER DEPTH OF AROUND 1500 FEET OR SO. SOME DECENT WARMING HAS TAKEN
PLACE TODAY DUE TO HIGHER 500 MB HEIGHTS MOVING INTO THE AREA.
TEMPERATURES AT 1 PM ARE 5-10 DEGREES HIGHER THAN AT THIS TIME
YESTERDAY.

FOR WEDNESDAY INTO THURSDAY...SURFACE HIGH PRESSURE WILL START TO
BUILD OVER THE GREAT BASIN...AND PRESSURE GRADIENTS WILL TREND A
LITTLE STRONGER OFFSHORE. THUS...SOME OF THE NORTHERN
MOUNTAINS...PASSES AND CANYONS MAY START TO SEE SOME GUSTY NORTH TO
NORTHEAST WINDS BY LATE WEDNESDAY AFTERNOON. A SHORT-WAVE TROUGH
MOVING THROUGH LATE WEDNESDAY INTO THURSDAY MORNING WILL PROVIDE
SOME MOMENTARY UPPER LEVEL SUPPORT FOR THE OFFSHORE WINDS...AS LOCAL
WRF INDICATES 850 MB NORTHEAST WINDS OF 15-30 KT EARLY THURSDAY
MORNING. MEANWHILE...OFFSHORE GRADIENTS LOOK TO PEAK THURSDAY
MORNING...AS MODELS GENERALLY SHOW 8-10 MB GRADIENTS FROM SAN DIEGO
TO TONOPAH...AND 11-13 MB GRADIENTS FROM SAN DIEGO TO SALT LAKE
CITY. CANSAC_WRF APPEARS TO BE THE MOST AGGRESSIVE WITH THE
NORTHEAST TO EAST WINDS FOR LATE WEDNESDAY NIGHT INTO THURSDAY
MORNING...AS IT SHOWS THE POTENTIAL FOR 50 MPH GUSTS ALONG THE
FAVORED COASTAL SLOPES/FOOTHILLS AND THROUGH MOUNTAIN PASSES AND
CANYONS. THE LOCAL WRF IS WEAKER WITH THE WINDS...BUT STILL SHOWS
35-40 MPH WIND GUSTS POSSIBLE FOR THESE AREAS...WHICH WOULD MEAN
THAT A WIND ADVISORY MAY BE NECESSARY. ALSO...A RIDGE WILL START TO
BUILD IN BEHIND THE DEPARTING SHORT-WAVE LATE WEDNESDAY
NIGHT...WHICH SHOULD HELP MAKE FOR A SHALLOWER MARINE LAYER. STRATUS
SHOULD GET SCOURED OUT BY THE DRY OFFSHORE FLOW IN ORANGE COUNTY BY
EARLY THURSDAY MORNING...WHILE IT MAY TAKE A BIT LONGER TO SCOUR OUT
IN SAN DIEGO COUNTY ALONG THE COAST...WITH DENSE FOG A POSSIBILITY
DUE TO THE INCREASINGLY SHALLOW MARINE LAYER.

THE RIDGE WILL CONTINUE TO BUILD OVER THE AREA DURING THE DAY
THURSDAY THROUGH SATURDAY. THIS...IN ADDITION TO CONTINUED WEAK TO
LOCALLY MODERATE OFFSHORE FLOW...WILL RESULT IN INCREASINGLY HOTTER
DAYS...WITH SATURDAY BEING THE HOTTEST DAY. DAY-TIME HIGH
TEMPERATURES WILL REACH 10-20 DEGREES ABOVE NORMAL ON SATURDAY
ANYWHERE FROM A FEW MILES INLAND ALL THE WAY TO THE COASTAL SLOPES.
THIS TRANSLATES TO DAY-TIME HIGHS REACHING THE LOW TO MID 100S IN
THE INLAND EMPIRE...UPPER 90S TO LOW 100S IN THE SAN DIEGO VALLEYS
AND INLAND ORANGE COUNTY...90S IN THE LOWER ELEVATIONS OF THE SANTA
ANA MOUNTAINS/FOOTHILLS...AND LOW TO MID 90S A FEW MILES INLAND OF
THE COAST. A HEAT ADVISORY HAS BEEN ISSUED FOR FRIDAY...SATURDAY AND
SUNDAY FOR THE VALLEYS...THE SANTA ANA  MOUNTAINS/FOOTHILLS...AND
THE LOWER MOUNTAIN SLOPES. A HEAT ADVISORY HAS ALSO BEEN ISSUED FOR
THE SAN DIEGO AND ORANGE COUNTY COASTAL AREAS FOR FRIDAY THROUGH
SATURDAY...WITH HIGHEST TEMPERATURES OCCURRING INLAND FROM THE
BEACHES. OFFSHORE FLOW WILL BE WEAKER FRIDAY AND SATURDAY...AS THERE
IS NO UPPER LEVEL SUPPORT TO SPEAK OF AND OFFSHORE GRADIENTS WILL BE
WEAKER.

SUNDAY THROUGH EARLY NEXT WEEK...PRESSURE GRADIENTS WILL GRADUALLY
TREND ONSHORE...WITH SLOW COOLING LIKELY FOR COASTAL AREAS AND THEN
EVENTUALLY SPREADING INLAND. HOWEVER...INITIALLY ON SUNDAY IT WILL
STILL BE QUITE HOT FOR THE VALLEYS AND MOUNTAINS...AND DAY-TIME HIGH
TEMPERATURES FOR MONDAY AND TUESDAY WILL STILL BE ABOVE NORMAL. THE
MARINE LAYER MAY NOT RETURN TO THE COAST UNTIL SUNDAY NIGHT.

&&

.AVIATION...
302015Z...COAST/VALLEYS...MOSTLY CLEAR SKIES WITH UNRESTRICTED VIS
WILL PREVAIL THROUGH AT LEAST EARLY EVENING. SOME STRATUS WILL
DEVELOP NEAR THE COAST AFTER 03Z...POSSIBLY REACHING COASTAL
AIRPORTS INCLUDING KSAN AND KCRQ BETWEEN 05Z AND 08Z...AND KSNA
AFTER 08Z. MOST CIGS WILL BE 700-1000 FT MSL WITH TOPS TO 1200 FT
MSL. LOCAL VIS BELOW 3 MI IN FOG COULD OCCUR ALONG COASTAL MESAS AND
OTHER HIGHER COASTAL TERRAIN BETWEEN 08Z AND 16Z WED...WITH A SMALL
CHANCE OF VIS BELOW 1 MI. MOST AREAS SHOULD CLEAR BY 17Z WED.

MOUNTAINS/DESERTS...CLEAR WITH UNRESTRICTED VIS THROUGH WED.

&&

.MARINE...
100 PM...NO HAZARDOUS MARINE WEATHER IS EXPECTED THROUGH SUNDAY.

&&

.FIRE WEATHER...
HIGH PRESSURE ALOFT AND OFFSHORE FLOW WITH LOCALLY GUSTY NORTHEAST
WINDS WILL BRING MUCH WARMER AND DRIER CONDITIONS FOR THURSDAY
THROUGH SUNDAY. STRONGEST WINDS...WITH LOCAL GUSTS TO AROUND 40
MPH...ARE EXPECTED FOR LATE WEDNESDAY NIGHT INTO THURSDAY
MORNING...FOLLOWED BY GRADUAL WEAKENING FRIDAY AND SATURDAY. FRIDAY
AND SATURDAY WILL BE THE WARMEST DAYS...ESPECIALLY INLAND WHERE
TEMPERATURES OF 95 TO 105 DEGREES ARE POSSIBLE. SLOW COOLING MAY
BEGIN NEAR THE COAST ON SUNDAY AS THE OFFSHORE PRESSURE GRADIENTS
CONTINUE TO WEAKEN. HUMIDITIES WILL FALL THURSDAY...REACHING THE MID
TEENS BY MID MORNING. EXPECT LOWEST DAYTIME HUMIDITIES OF 5 TO 10
PERCENT FOR INLAND AREAS FRIDAY AND SATURDAY WITH POOR OVERNIGHT
RECOVERY. HUMIDITIES ARE EXPECTED TO SLOWLY RECOVER FOR SUNDAY INTO
EARLY NEXT WEEK AS WEAK ONSHORE FLOW RETURNS. WHILE RED FLAG WARNING
CRITERIA MAY NOT BE MET DURING THIS PERIOD...THERE WILL STILL BE AN
ELEVATED THREAT FOR WILDFIRES FOR THURSDAY INTO SUNDAY.

&&

.SKYWARN...
SKYWARN ACTIVATION WILL NOT BE NEEDED TODAY.

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...HEAT ADVISORY FROM 11 AM FRIDAY TO 8 PM PDT SATURDAY FOR THE
     ORANGE COUNTY COASTAL AREAS...SAN DIEGO COUNTY COASTAL
     AREAS.

     HEAT ADVISORY FROM 11 AM FRIDAY TO 8 PM PDT SUNDAY FOR THE
     RIVERSIDE COUNTY MOUNTAINS...SAN BERNARDINO COUNTY
     MOUNTAINS...SAN BERNARDINO AND RIVERSIDE COUNTY VALLEYS-THE
     INLAND EMPIRE...SAN DIEGO COUNTY MOUNTAINS...SAN DIEGO
     COUNTY VALLEYS...SANTA ANA MOUNTAINS AND FOOTHILLS.

PZ...NONE.

&&

$$

PUBLIC...HARRISON
AVIATION/MARINE...MAXWELL
FIRE WEATHER...PG




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