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208
FXUS66 KSGX 271613
AFDSGX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
813 AM PST THU NOV 27 2014

.SYNOPSIS...
IT WILL BE ANOTHER VERY WARM DAY WITH TEMPERATURES RUNNING WELL
ABOVE AVERAGE WEST OF THE MOUNTAINS. THE WEATHER WILL BEGIN TO TURN
ON FRIDAY AS THE OFFSHORE WEAKENS AND MARINE AIR SPREADS INLAND.
THIS WILL BRING A COOLING TREND...HIGHER HUMIDITY...AND A RETURN OF
NIGHT AND MORNING COASTAL LOW CLOUDS AND FOG. LOW PRESSURE OVER THE
EASTERN PACIFIC IS EXPECTED TO BEGIN TO SPREAD A DEEPER MOIST LAYER
OVER CALIFORNIA SOMETIME NEXT WEEK. TIMING IS UNCERTAIN...BUT EXPECT
MORE CLOUDS AND A CHANCE OF SOME PRECIPITATION.

&&

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

SKIES WERE CLEAR ACROSS THE SOUTHLAND THIS MORNING AND AT 8 AM
PST...TEMPERATURES IN MANY AREAS WERE RUNNING ABOUT 5 DEGREES F
HIGHER THAN OBSERVED YESTERDAY. SURFACE PRESSURE GRADIENTS WERE UP
TO 10 MBS OFFSHORE FROM NV...AND 1-2 MBS OFFSHORE FROM THE LOWER
DESERTS. THE OFFSHORE GRADIENTS WERE STILL SUPPORTING EASTERLY WIND
SPEEDS OF 15-20 MPH WITH GUSTS OVER 30 MPH ALONG THE COASTAL
FOOTHILLS OF SAN DIEGO COUNTY. RH VALUES WERE EXTREMELY LOW IN THESE
AREAS AT 6-12 PERCENT.

IT WILL BE A VERY WARM DAY...PERHAPS THE WARMEST OF THIS EVENT WITH
MANY AREAS WELL INTO THE 80S...AND MORE SPOTS IN THE 90S. EASTERLY
WINDS WILL BE GUSTY IN WIND PRONE AREAS ONE MORE DAY...AND THEN
GRADUALLY WEAKEN THIS EVENING. FOR FRI...CHANGES WILL DEVELOP. FIRST
OFF...VERY LITTLE OFFSHORE WIND ALONG THE FOOTHILLS IN THE
MORNING...THEN ONSHORE FLOW WILL BEGIN TO ADVECT A SHALLOW MARINE
LAYER OVER THE COASTAL STRIP. IT WILL ALSO BE MUCH COOLER ALONG THE
IMMEDIATE COAST. AND SLIGHTLY COOLER INLAND AS WELL.

THE STRONG RIDGE OF HIGH PRESSURE OVERHEAD WILL SLOWLY CAVE INTO THE
WEEKEND. THIS WILL ALLOW SFC PRESSURE TO FALL OVER THE GREAT BASIN
AND BRING A BROAD RETURN OF ONSHORE FLOW ACROSS CA. RAIN WILL
DEVELOP ACROSS NORTHERN PORTIONS OF THE STATE AS A PLUME OF HIGH PW
AIR INTERACTS WITH WAVES OF LOW PRESSURE SPUN OFF OF A LARGE AREA OF
LOW PRESSURE COVERING THE EASTPAC. THIS FEATURE MAY EVENTUALLY
BRING RAIN TO SOUTHERN PORTIONS OF THE STATE SOMETIME NEXT WEEK BUT
TIMING IS UNCERTAIN.

WEATHER CONCERNS IN THE NEAR TERM...OTHER THAN THE EXTREME DRYNESS
AND ELEVATED WILDFIRE THREAT TODAY...DENSE FOG. LOOKS LIKE THERE
WILL BE A CHANCE OVER COASTAL AREAS ON FRI NIGHT INTO SAT MORNING.
AFTER THAT...AN EDDY SHOULD PROP UP THE MARINE LAYER AND ASSOCIATED
CLOUDS/FOG. THIS WOULD KEEP ANY DENSE FOG THREAT FARTHER INLAND AND
AWAY FROM THE COASTAL AIRPORTS.

FROM PREVIOUS DISCUSSION...

SUNDAY THROUGH WEDNESDAY...
THE GLOBAL MODELS CONTINUE TO DIVERGE FROM SUNDAY THROUGH WEDNESDAY
IN TWO KEY AREAS...THE LOW PRESSURE SYSTEM OVER THE EASTERN
PACIFIC...AND A DOWNSTREAM TROUGH OF LOW PRESSURE EAST FOR THE
ROCKIES. THE ECMWF IS MORE AMPLIFIED WITH A TROUGH OF LOW PRESSURE
OVER THE CENTRAL AND EASTERN STATES NEXT TUESDAY AND WEDNESDAY...AND
IN TURN SLOWER AND MORE CLOSED WITH THE LOW PRESSURE SYSTEM OVER THE
EASTERN PACIFIC. THE OPERATIONAL ECMWF HAS BEEN CONSISTENT WITH
ITSELF FOR THE PAST 24 HOURS AND THE ECMWF ENSEMBLE MEAN HAS TRENDED
SLOWER AND MORE CLOSED OVER THE PAST 24 HOURS AND IS NOW
ALMOST...BUT NOT QUITE...AS SLOW AND CLOSED AS THE OPERATIONAL
ECWMF. THE GEM HAS ALSO TRENDED MUCH CLOSER TO THE ECMWF FOR THE
EARLY TO MIDDLE PART OF NEXT WEEK...BOTH OVER THE CENTRAL AND
EASTERN STATES...AND OVER THE EASTERN PACIFIC. THE GFS...BOTH THE
OPERATIONAL RUN AND THE 13-KM PARALLEL RUN...AND THE GFS ENSEMBLE
MEAN HAVE BEEN CONSISTENT WITH THEMSELVES THE PAST PAST 24 HOURS.
THE GFS IS LESS AMPLIFIED OVER THE CENTRAL AND EASTERN STATES AND IN
TURN NOT AS SLOW...BUT WITH A CLOSED LOW TO MOVE INLAND ALONG THE
CALIFORNIA COAST THE EARLY TO MIDDLE PART OF NEXT WEEK. THE GFS
SOLUTIONS WOULD BRING SIGNIFICANT PRECIPITATION TO SOUTHERN
CALIFORNIA...MAINLY TUESDAY INTO TUESDAY NIGHT. THE ECMWF WOULD NOT
ONLY BE SLOWER WITH PRECIPITATION ARRIVAL INTO SOUTHERN
CALIFORNIA...BUT WOULD BRING LESS AS WELL AS THE LOW PRESSURE SYSTEM
WOULD WEAKEN AND MOVE INLAND TO THE NORTH AS IT APPROACHES THE
CALIFORNIA COAST. THE CURRENT FORECAST CONTINUES TO LEAN TOWARDS THE
GFS...BUT POPS CONTINUE TO REMAIN LOWER THAN A PURELY GFS SOLUTION
WOULD IMPLY GIVEN THE CONTINUING UNCERTAINTY.

&&

.AVIATION...
271600Z...VFR CONDITIONS WITH FEW/SCT HIGH CLOUDS THROUGH FRIDAY
MORNING.

&&

.MARINE...
800 AM...NO HAZARDOUS MARINE WEATHER IS EXPECTED THROUGH SUNDAY.
ISOLATED SHOWERS AHEAD OF A STORM SYSTEM COULD DEVELOP OVER THE
COASTAL WATERS MONDAY.

&&

.FIRE WEATHER...
EXTREMELY LOW RH...DAYTIME TEMPERATURES CLIMBING INTO THE 80S TO
LOWER 90S...AND LOCALLY GUSTY EASTERLY WINDS ALONG THE FOOTHILLS...
WILL CONTINUE ELEVATED FIRE WEATHER CONDITIONS THROUGH TODAY.

EXPECT SOME IMPROVEMENT ON FRI AS THE OFFSHORE WEAKENS AND THE SEA
BREEZE DEVELOPS. THERE WILL BE SOME RETURN OF MOISTURE ALONG THE
COASTAL STRIP...BUT INLAND...MINIMUM RH WILL REMAIN BELOW 15
PERCENT. BETTER RECOVERY ON SATURDAY.

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...NONE.

&&

$$

PUBLIC/FIRE WEATHER...JAD
EXTENDED DISCUSSION...17
AVIATION/MARINE...TS













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