Weather Service Report


691 
FXUS66 KSGX 160336
AFDSGX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
833 PM PDT MON SEP 15 2014

.SYNOPSIS...
MOISTURE FROM HURRICANE ODILE WILL SPREAD NORTHWARD OVERNIGHT 
THROUGH WEDNESDAY...ELEVATING THE CHANCE FOR SHOWERS AND 
THUNDERSTORMS ACROSS SOUTHERN CALIFORNIA. SOME OF THE STORMS WILL 
PRODUCE HEAVY RAINFALL AND THERE WILL BE A THREAT OF FLASH 
FLOODING...ESPECIALLY AFTERNOONS AND EVENINGS NEAR THE MOUNTAINS. 
THERE WILL NOT BE MUCH RELIEF FROM THE HEAT AND HUMIDITY UNTIL 
THURSDAY WHEN A TROUGH OF LOW PRESSURE BRINGS COOLING AND DRYING 
FROM THE NORTHWEST. ISOLATED SHOWERS AND THUNDERSTORMS ARE STILL 
POSSIBLE INTO FRIDAY OVER THE MOUNTAINS AND DESERTS...THEN PARTLY 
CLOUDY WEATHER WITH SEASONAL TEMPERATURES NEXT WEEKEND.

&&

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

NO MAJOR CHANGES TO THE FORECAST. SLIGHTLY HIGHER DAYTIME 
TEMPERATURES FOR COASTAL AREAS TUE/WED.

IT WAS ANOTHER HOT DAY ACROSS THE REGION WITH MANY SITES TYING OR 
SETTING RECORD HIGH MINIMUMS. EVEN A FEW RECORD MAXIMUM TEMPERATURES 
WERE TIED/SET. THE NEARSHORE BUOYS ALL CONTINUE TO INDICATE SEA 
TEMPS IN THE LOWER TO MIDDLE 70S. THIS WILL LIKELY RESULT IN MORE 
RECORD HIGH MINIMUMS OVER THE NEXT FEW DAYS. AT 8 PM PDT... 
TEMPERATURES WERE STILL IN THE 80S AND 90S. THE 00Z MIRAMAR SOUNDING 
STILL HAD NW FLOW AROUND 10 KT BELOW 5K FT...BUT ALOFT...A DEEPER 
LAYER OF 10-20 KT EASTERLY WINDS HAD DEVELOPED UP THROUGH 22K FT. PW 
WAS JUST BELOW 1.5 INCH. AT 7 PM PDT...THE GULF SURGE WAS UNDERWAY 
AS THE WIND AT YUMA TURNED SOUTHERLY 15KT WITH A LARGE DEWPOINT JUMP.

TROPICAL CYCLONE ODILE IS INDEED WEAKENING THIS EVENING AS IT DRIFTS 
NORTHWARD ALONG THE BAJA PENINSULA. THE STORM HAS FALLEN BELOW 
HURRICANE STRENGTH AND WILL CONTINUE TO WIND DOWN THROUGH TUE AS IT 
NAVIGATES THE MOUNTAINS OF THE BAJA PENINSULA ON A NW COURSE...THEN 
TURNS EAST INTO THE NORTHERN GULF OF CALIFORNIA WED. AHEAD OF THIS 
STORM...A SURGE OF LOW-LEVEL MOISTURE IS FORECAST TO RIDE NORTHWARD 
THROUGH THE LOWER COLORADO RIVER VALLEY. THE SURGE MAY GENERATE SE 
WINDS OF 15-20KT AND RESULT IN LOW CLOUDS INTO THE COACHELLA VALLEY 
BY MORNING. DEPENDING ON THE DEPTH OF THE MOISTURE...IT MAY BE ABLE 
TO FUEL THUNDERSTORM DEVELOPMENT ALONG AND EAST OF THE MOUNTAINS ON 
TUE. DEEPER MOISTURE WILL FOLLOW INTO THE MID-LEVELS ON WED WHEN THE 
CHANCE OF THUNDERSTORMS LOOKS GREATEST.

THE HIGH PRESSURE RIDGE ALOFT OVER THE REGION WILL BUILD NORTHWARD 
INTO THE GREAT BASIN THROUGH WED AS A LONGWAVE TROUGH SWINGS NE OFF 
THE PACIFIC TOWARD CENTRAL CA. THE MODELS HAVE BEEN INDICATING A 
SLIGHT INCREASE IN THE OFFSHORE GRADIENT OVER THE REGION TUE/WED. 
THIS WILL HAVE IMPLICATIONS FOR COASTAL AREAS IF IT MATERIALIZES 
WITH SOME ADDITIONAL WARMING SPREADING WESTWARD. THE INLAND AREAS 
MAY HAVE PEAKED AND WILL STAY WARM WITH INCREASING HUMIDITY...AND
OVERNIGHT MINIMUMS WILL REMAIN WELL ABOVE AVERAGE.

FORECAST CONFIDENCE IS LOWER FOR THE NEXT COUPLE OF DAYS AS ODILE 
GETS CLOSER. INDIRECT CIRCULATIONS AROUND THE STORM MAY INFLUENCE 
OUR WEATHER IN WAYS NOT PROPERLY MODELED. FOR EXAMPLE SFC 
PRESSURE...MOISTURE...AND OMEGA FIELDS...MCS DEVELOPMENT...OR 
UNEXPECTED WARMING IN SOME AREAS. THE 18Z NAM12 GUIDANCE DID 
INDICATE SOME WARMING ALONG THE COAST TUE/WED WITH INCREASED 
OFFSHORE FLOW...HOWEVER IT ALSO HAD INCREASING INSTABILITY AND 
RAINFALL OVER COASTAL AREAS ON THU MORNING. THE RAIN IS NOT EXPECTED 
OR INDICATED ON OTHER GLOBAL MODELS...BUT WITH THE LARGE AMOUNT OF 
MOISTURE FROM AN ANOMALOUS FEATURE LIKE ODILE ENTERING 
THE DOMAIN...AND AN APPROACHING UPPER TROUGH...IT CANNOT BE RULED 
OUT.      

FOR NOW WE ARE EXPECTING THUNDERSTORMS TO BECOME MORE NUMEROUS 
TUE...AND PEAK ON WED BEFORE DRIER AIR SWEEPS IN FROM THE NW WITH 
THE APPROACHING PACIFIC TROUGH. AHEAD OF THE TROUGH...STEERING 
CURRENTS ARE MODERATE EASTERLY...SO EXPECT SOME ACTIVITY W OF THE 
MTNS. BY LATE THU INTO FRI...THE TROUGH SHOULD CLEAR ANY SHOWER 
THREAT FROM THE COAST...BUT THE MTNS/DESERTS MAY STILL HAVE ENOUGH 
MOISTURE AND INSTABILITY TO GET SCATTERED SHWRS/TSTMS THROUGH FRI 
AFTERNOON. THE MARINE LAYER WILL DEEPEN AND COOL AREAS WEST OF THE 
MOUNTAINS INTO THE WEEKEND.

&&

.AVIATION...
160300Z...THERE IS A SMALL CHANCE THAT LOW CLOUDS AND FOG COULD FORM 
WITHIN 5 SM OF THE COAST BETWEEN 09Z AND 15Z...BUT CONFIDENCE IS TOO 
LOW TO INCLUDE IN THE TAFS. OTHERWISE...MOSTLY CLEAR WITH 
UNRESTRICTED VIS THROUGH TUESDAY MORNING.

BETWEEN 18Z TUE AND 03Z WED...SCT-BKN CLOUDS LAYERED FROM 8000 FT 
MSL TO 35000 FT WITH ISOLATED THUNDERSTORMS/SHOWERS OVER THE 
MOUNTAINS...DESERTS...EASTERN SAN DIEGO VALLEYS AND THE INLAND 
EMPIRE. KONT...KPSP AND KTRM MAY BE IMPACTED...BUT CONFIDENCE IS LOW.

&&

.MARINE...
800 PM...NO HAZARDOUS MARINE WEATHER EXPECTED THROUGH SATURDAY.

&&

.SKYWARN... 
SKYWARN ACTIVATION MAY BE NEEDED ON TUESDAY AFTERNOON AND WILL 
LIKELY BE NEEDED ON WEDNESDAY.

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...HEAT ADVISORY UNTIL 7 PM PDT TUESDAY FOR THE ORANGE COUNTY 
     COASTAL AREAS...SAN BERNARDINO AND RIVERSIDE COUNTY 
     VALLEYS-THE INLAND EMPIRE...SAN DIEGO COUNTY VALLEYS...
     SANTA ANA MOUNTAINS AND FOOTHILLS.

PZ...NONE.

&&

$$

PUBLIC...JAD
AVIATION/MARINE...PG










Return to Home page


Western Regional Climate Center, wrcc@dri.edu