EXTREME SOUTHWESTERN CALIFORNIA AREA FORECAST DISCUSSION
NWS SAN DIEGO CA
AFDSAN 200 PM PDT MON APR 30 2001
...SYNOPSIS...
ONSHORE FLOW AND A MARINE LAYER WILL CONTINUE THE COASTAL LOW CLOUDS
AND FOG THROUGH WEDNESDAY MORNING. HIGH PRESSURE ALOFT WILL BRING
ANOTHER VERY WARM DAY TO THE MOUNTAINS AND DESERTS TUESDAY BEFORE
NORTH FLOW ALOFT...ASSOCIATED WITH LOW PRESSURE ALOFT OVER THE GREAT
BASIN...BRINGS A COOLING TREND. STRONG GUSTY WINDS ARE EXPECTED OVER
THE MOUNTAINS AND DESERTS WEDNESDAY...SPREADING TO SOME CANYONS WEST
OF THE MOUNTAINS BY THURSDAY MORNING. HIGH PRESSURE ALOFT WILL
GRADUALLY REBUILD BY THE WEEKEND TO BRING WARMING INLAND BUT A
RETURN OF LOW CLOUDS AND FOG AT THE COAST.
...DISCUSSION...
LOW CLOUDS AND FOG FORMED WITHIN ROUGHLY 20-25 MILES OF THE COAST
LAST NIGHT...AND THIS AFTERNOON STILL LINGERED ALONG THE SAN DIEGO
AND SOUTHERN ORANGE COUNTY COASTS...IN PART DUE TO THE
INVERSION...WHICH BASED ON ACARS WAS 10 DEG C STRONG JUST MINUTES
AGO AND AT AROUND 1500 FEET. THE INVERSION SHOULD BE ALMOST AS
STRONG TUESDAY SINCE THE TEMPS SHOULD REMAIN ABOUT THE SAME ABOVE
THE INVERSION...BUT ON WEDNESDAY...WE WILL START TO SEE COLD AIR
ADVECTION ALOFT WEAKENING THE INVERSION...AND BY THURSDAY...THE LOW
CLOUDS SHOULD BE GONE. THE INVERSION HEIGHT SHOULD INCREASE
SOME...MAINLY TUESDAY AS THE ONSHORE FLOW INCREASES AND THE EDDY
STRENGTHS A BIT...BUT NOT ENOUGH TO REACH THE MTNS...OTHER THAN SOME OF
THE SANTA ANA MTNS. NEVERTHELESS...SOME COOLING SHOULD OCCUR WEST OF
THE MTNS TUESDAY.
FOR WEDNESDAY...THE BATTLE WILL BASICALLY BE BETWEEN THE EDDY AND
THE OFFSHORE TRENDS...AND HERE I SIDED WITH THE MSO WHICH HAS WEAKER
OFFSHORE TRENDS. SO...THE LOW CLOUDS AND FOG SHOULD BE EXTENSIVE IN
THE MORNING BUT SHOULD EVENTUALLY CLEAR TO THE COAST BY AFTERNOON.
THE MTNS/DESERTS WILL CERTAINLY BE WINDY WITH THE TREND TOWARDS N/NW
FLOW ALOFT...BUT THE CANYONS WEST OF THE MTNS SHOULD NOT BE WINDY
UNTIL WED NIGHT/THU AM WHEN THE SURFACE GRADIENTS BECOME OFFSHORE
AND THE CAA IS AT ITS STRONGEST. TEMPS WILL DECREASE NEARLY 10 DEG F
PER DAY WED AND THU OVER THE MTNS/DESERTS. OVERALL...THE CLOSED
LOW...BASED ON VARIOUS AVN/MRF SOLUTIONS...WHICH ARE MORE CLOSELY
ALIGNED ON THE ENSEMBLE THAN BEFORE...SHOULD STAY FAR ENOUGH NE TO
KEEP CLOUDS AWAY FROM THE MTNS...AND THE RH VALUES ARE PROGGED TO
INCREASE ONLY FROM ABOUT E SAN BERN CO AND POINTS N AND E FROM
THERE. I DO NOT FAVOR THE MORE WESTERLY UKMET AS IT INITIALIZED
POORLY...NOR DO I FAVOR THE NOGAPS...WHICH LIKE THE UKMET HAS TOO
SHARP OF A TURN SOUTH FOR THE MAIN VORT MAX ONCE IT VENTURES EAST OF
THE CASCADES TUE. ECM CONTINUES TO HAVE THE LOW EAST OF THE MRF
SOLUTION. IT APPEARS THAT THE LOW PRESSURE EXITS THE REGION BY
SAT...SO A RETURN TO WEATHER NOT ALL THAT DIFFERENT FROM WHAT WE
HAVE TODAY SHOULD OCCUR.
SAN 0000
.SAN...NONE.
MAXWELL
EXTREME SOUTHWESTERN CALIFORNIA AREA FORECAST DISCUSSION
NWS SAN DIEGO CA
AFDSAN 930 AM PDT MON APR 30 2001
...SYNOPSIS...
HIGH PRESSURE ALOFT AND WEAK ONSHORE FLOW WILL BRING FAIR WARM
WEATHER THROUGH TUESDAY...EXCEPT FOR SOME COASTAL NIGHT AND MORNING
LOW CLOUDS AND FOG. THE FLOW ALOFT WILL BECOME MORE NORTHERLY
WEDNESDAY AS LOW PRESSURE ALOFT MOVES THROUGH THE GREAT BASIN. THIS
WILL BRING COOLING TO THE MOUNTAINS AND DESERTS AND A DECREASE IN
THE LOW CLOUDS AND FOG WEST OF THE MOUNTAINS. HIGH PRESSURE ALOFT
SHOULD RETURN NEXT WEEKEND FOR GENERALLY FAIR WEATHER EXCEPT FOR THE
COASTAL LOW CLOUDS AND FOG.
...DISCUSSION...
LOW CLOUDS AND FOG FORMED WITHIN ROUGHLY 20-25 MILES OF THE COAST
LAST NIGHT AND ARE GRADUALLY CLEARING THIS MORNING. THE COASTAL EDDY
WAS WEAKER...AS EXPECTED...AND SO ARE THE ONSHORE PRESSURE
GRADIENTS. THE INVERSION HAS LOWERED TO ABOUT 1500 FEET...DOWN A BIT
FROM THE 12Z SOUNDING...BASED ON OBS AND ACARS. HOWEVER...THE
INVERSION STRENGTH IS NEARLY 10 DEG C...SO SOME BEACHES...AND
CERTAINLY THE COASTAL WATERS WILL HAVE TROUBLE CLEARING. EVERYWHERE
MORE THAN ABOUT A MILE INLAND SHOULD CLEAR BEFORE NOON.
THERE IS SIGNIFICANT WARMING ABOVE THE INVERSION...AND WITH THAT
PLUS THE LOWERING OF THE INVERSION HEIGHT...TEMPS WILL INCREASE
GREATLY OVER THE MTNS AND FOOTHILLS. THE ALPINE RAWS WAS ALREADY 74
AT 9 AM...AND MOST MOUNTAIN LOCATIONS SHOULD BE 5-10 DEG F WARMER
THAN ON SUNDAY...WHICH WOULD PLACE TEMPS GENERALLY IN THE UPPER
RANGE OF THE CURRENT FORECAST.
SOME COOLING SHOULD OCCUR WEST OF THE MTNS TUESDAY DUE TO STRONGER
ONSHORE FLOW...AND WITH A STRONG INVERSION EXPECTED...LOW CLOUDS MAY
BE TOUGH TO CLEAR IN SOME AREAS. THIS WILL BE HANDLED IN THE
AFTERNOON PACKAGE. BEYOND TUES...THE MODELS ARE TRENDING A BIT
FURTHER NE WITH THE INSIDE SLIDER...THOUGH THIS WILL BE ANALYZED
FURTHER WHEN THE 12Z AVN/NOGAPS ARE COMPLETED. WITH THE MORE INLAND
TREND...EXPECT FEWER CLOUDS AND LESS COOLING THAN PREVIOUSLY THOUGHT
FOR THE MTNS/N DESERTS. OFFSHORE FLOW LOOKS LIKELY THU AM...SO WE
MAY BE GUSTY BELOW PASSES AND CANYONS THEN WITH LITTLE OR NO MARINE
LAYER. THE PASS/CANYON WINDS COULD START WED AM DUE TO SOME COLD AIR
ADVECTION...THOUGH THE WINDS WOULD BE PRIMARILY THE MOST FAVORED N-S
CANYONS AS LOW-LEVEL FLOW WILL STILL BE ONSHORE TO THE EAST. EXPECT
THE MARINE LAYER NEAR THE COAST AND WARMING OVER THE MTNS/DESERTS
TO RETURN BY SAT DUE TO ONSHORE FLOW AS WEAK HIGH PRESSURE REFORMS
ALOFT.
SAN 000
.SAN...NONE.
MAXWELL