Area Forecast Discussion
Issued by NWS San Diego, CA

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS66 KSGX 262135
AFDSGX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
135 PM PST WED NOV 26 2014

.SYNOPSIS...
HIGH PRESSURE ALOFT AND WEAKENING OFFSHORE FLOW WILL BRING A WARMING
TREND INTO THANKSGIVING DAY WITH WELL ABOVE AVERAGE HIGH
TEMPERATURES FOR THE COAST AND VALLEYS. A RETURN OF ONSHORE FLOW
WILL BRING A COOLING TREND FOR FRIDAY THROUGH THE WEEKEND AND A
RETURN OF NIGHT AND MORNING COASTAL AND VALLEY LOW CLOUDS AND FOG.
FOR TUESDAY THROUGH WEDNESDAY OF NEXT WEEK...A PACIFIC LOW PRESSURE
SYSTEM COULD BRING MODERATE TO HEAVY PRECIPITATION.

&&

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

VISIBLE SATELLITE SHOWS CLEAR SKIES ACROSS THE REGION THIS
MORNING...AND WIND OBSERVATIONS INDICATE WEAK OFFSHORE WINDS
OCCURRING AT THE SURFACE. THE 12Z MIRAMAR SOUNDING SHOWS A DRY
PROFILE...WITH SIGNIFICANT 24 HOUR WARMING FROM THE SURFACE TO 700
MB. THIS WARMER AND DRY ATMOSPHERE IS DUE TO THE AFOREMENTIONED
OFFSHORE FLOW AND AN UPPER LEVEL RIDGE ALONG THE CALIFORNIA COAST.
PRESSURE GRADIENTS WILL REMAIN WEAKLY OFFSHORE THROUGH
THURSDAY...WITH SOME LOCAL 35 MPH GUSTS THROUGH THE PASSES/CANYONS
AND ALONG THE COASTAL SLOPES AND FOOTHILLS AT TIMES. TEMPERATURES
ARE CURRENTLY SEVERAL DEGREES HIGHER THAN 24 HOURS AGO...WITH A FEW
LOCATIONS 10 DEGREES HIGHER THAN THIS TIME YESTERDAY. THANKSGIVING
WILL BE THE WARMEST DAY...WITH DAY-TIME HIGHS 10-20 DEGREES ABOVE
NORMAL...AS HIGHS REACH INTO THE MID TO UPPER 80S FOR THE VALLEYS
AND AREAS A COUPLE MILES FROM THE COAST.

THE UPPER LEVEL RIDGE WILL BREAK DOWN ON FRIDAY...WITH ZONAL FLOW
ALOFT AND PRESSURE GRADIENTS TURNING BACK ONSHORE. IT IS POSSIBLE
THAT WE COULD START TO SEE SOME FOG ALONG THE COAST AS EARLY AS
FRIDAY MORNING. FRIDAY WILL BE THE START OF A COOLING TREND WHICH
WILL CONTINUE THROUGH THE WEEKEND AS ONSHORE FLOW AT THE SURFACE AND
ZONAL FLOW ALOFT CONTINUE. THE MARINE LAYER WILL DEEPEN AS
WELL...WITH NIGHT AND MORNING LOW CLOUDS/FOG LIKELY MOVING INTO THE
COAST AND WESTERN VALLEYS FRIDAY NIGHT/SATURDAY MORNING...AND THEN
FARTHER INTO THE VALLEYS SATURDAY NIGHT/SUNDAY MORNING AND SUNDAY
NIGHT/MONDAY MORNING. DAY-TIME HIGHS WILL START TO FALL TO NEAR TO
SLIGHTLY BELOW NORMAL FOR THE MOUNTAINS AND WEST ON SUNDAY...AND
REMAINING SLIGHTLY ABOVE NORMAL FOR THE DESERTS. THE MODELS SHOW A
SHORTWAVE TROUGH MOVING INLAND OVER CENTRAL AND NORTHERN CALIFORNIA
ON SUNDAY WHICH THE ECMWF INDICATES COULD SQUEEZE OUT SOME VERY
LIGHT PRECIPITATION OVER SOUTHERN CALIFORNIA...BUT THE FORECAST
REMAINS DRY FOR THAT TIME PERIOD DUE TO LOW CONFIDENCE AND MODEL
DISAGREEMENT.

FOR LATE MONDAY INTO WEDNESDAY...MODELS CONTINUE TO SHOW A STORM
SYSTEM WHICH WILL LIKELY BRING MODERATE TO HEAVY PRECIPITATION
TOTALS TO SOUTHERN CALIFORNIA. THE 12Z GFS AND GEM ARE NOW IN GOOD
AGREEMENT WITH BRINGING THE SYSTEM THROUGH THE AREA A BIT QUICKER
THAN THE 12Z ECMWF. ALL THREE MODELS SHOW SOUTHWEST FLOW AHEAD OF
THE SYSTEM WHICH IS ABLE TO TAP INTO SUB-TROPICAL MOISTURE AND BRING
IT UP OVER SOUTHERN CALIFORNIA EARLY TUESDAY MORNING...RESULTING IN
WIDESPREAD STRATIFORM RAIN WHICH CONTINUES INTO LATE TUESDAY. GFS
PRECIPITABLE WATER SHOWS 1.3 INCHES ASSOCIATED WITH THIS
SUB-TROPICAL MOISTURE. DURING THIS WARM PORTION OF THE STORM...SNOW
LEVELS LOOK TO REMAIN VERY HIGH AT AROUND 9000-11000 FEET. THE 12
GFS REMAINS QUICKER WITH THE ARRIVAL OF THE COLD AIR...DROPPING SNOW
LEVELS TO AROUND 7000 FEET BY EARLY WEDNESDAY MORNING...WHILE THE
12Z ECMWF DOES NOT REALLY BRING THE COLDER AIR INTO THE REGION UNTIL
WEDNESDAY AFTERNOON. THUS...MOST OF THE SNOWFALL IS LIKELY NOT TO
OCCUR UNTIL WEDNESDAY...WITH PRECIPITATION MOSTLY IN THE FORM OF
RAIN OVER THE MOUNTAINS ON TUESDAY. THE 12Z ECMWF REMAINS THE
SLOWEST SOLUTION...WITH THE TROUGH AXIS NOT MOVING INLAND UNTIL
WEDNESDAY AFTERNOON/EVENING...AND PRECIPITATION CONTINUING THROUGH
LATE WEDNESDAY NIGHT. PRECIPITATION TOTALS FOR THE SYSTEM STILL LOOK
LIKE THEY WILL BE SIGNIFICANT...WITH 1-2 INCHES AT THE COAST...2-3
INCHES IN THE VALLEYS...3-4 INCHES OR GREATER IN THE MOUNTAINS...AND
LESS THAN AN INCH IN THE DESERTS. WITH GOOD SOUTH TO SOUTHWEST FLOW
AT 850 MB AHEAD OF THE COLD FRONT PASSAGE ON TUESDAY...THE HEAVIEST
PRECIPITATION MAY FOCUS OVER THE SOUTHERLY FACING SAN BERNARDINO
COUNTY MOUNTAINS. THE 12Z GFS BRINGS THE TROUGH AXIS THROUGH THE
AREA WEDNESDAY MORNING INTO WEDNESDAY AFTERNOON...WITH PRECIPITATION
ENDING WEDNESDAY EVENING. THE AMOUNT OF SNOW THAT FALLS WILL LARGELY
DEPEND ON HOW MUCH PRECIPITATION OCCURS AFTER THE COLD AIR MOVES IN.
THE ECMWF REMAINS THE HEAVIEST WITH THE COLD FRONTAL AND
POST-FRONTAL PRECIPITATION...BUT ALSO BRINGS WET-BULB ZERO
TEMPERATURES DOWN TO ONLY 8000 FEET...WITH SIGNIFICANT SNOWFALL
POSSIBLE ABOVE THAT ELEVATION. WEST TO SOUTHWEST WINDS WILL BECOME
GUSTY AS WELL...WITH STRONGEST WINDS IN THE MOUNTAINS AND DESERTS
WHERE 50 MPH GUSTS OR GREATER WILL BE POSSIBLE. FINALLY...DAY-TIME
HIGHS WILL FALL TO A FEW DEGREES BELOW NORMAL BY TUESDAY.

&&

.AVIATION...
262100Z...CLEAR SKIES WITH UNRESTRICTED VIS THROUGH THURSDAY.

&&

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

&&

.FIRE WEATHER...
WEAK OFFSHORE WINDS WILL CONTINUE INTO THURSDAY...WITH POOR
OVERNIGHT RECOVERIES TONIGHT. THE OFFSHORE WINDS AND UPPER LEVEL
RIDGE WILL RESULT IN HIGH TEMPERATURES 10-20 DEGREES ABOVE NORMAL
FOR THANKSGIVING AND MINIMUM HUMIDITY IN THE UPPER SINGLE DIGITS/LOW
TEENS. THIS WILL RESULT IN CONTINUED ELEVATED FIRE WEATHER
CONDITIONS. THEN...ONSHORE FLOW WILL START TO RETURN LATE THURSDAY
NIGHT INTO FRIDAY...WITH SOME INCREASE IN HUMIDITIES AND COOLER
CONDITIONS FOR FRIDAY. COOLING AND INCREASING HUMIDITY WILL CONTINUE
INTO THE WEEKEND AS A TROUGH APPROACHES THE WEST COAST AND THE
MARINE LAYER RETURNS AND DEEPENS. THIS TROUGH WILL EVENTUALLY MOVE
OVER THE AREA EARLY NEXT WEEK...LIKELY BRINGING WIDESPREAD
SIGNIFICANT WETTING PRECIPITATION.

&&

.SKYWARN...
SKYWARN ACTIVATION IS NOT REQUESTED. HOWEVER WEATHER SPOTTERS ARE
ENCOURAGED TO REPORT SIGNIFICANT WEATHER CONDITIONS.

&&

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

&&

$$

PUBLIC/FIRE WEATHER...HARRISON
AVIATION/MARINE...TS




USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.