SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NWS LOS ANGELES/OXNARD CA
AFDLOX 910 PM PDT FRI SEP 3 1999
PROFILER AND ACARS DATA SHOWS THE MARINE LAYER THIS EVENING WAS ABOUT
2000 TO 2500 FEET DEEP. EXPECT THE MARINE LAYER TO REMAIN ABOUT THE
SAME OR EVEN COME DOWN SLIGHTLY OVERNIGHT. THE FOG PRODUCT WAS SHOWING
SOME LOW CLOUDS OVER THE LAX/VTU COASTS AND ALONG THE SLO COUNTY
COAST...WHILE THE SBA COUNTY CENTRAL COAST WAS SOCKED IN WITH LOW
CLOUDS. WITH W TO E GRADIENTS STILL DECENTLY ONSHORE (+5.2 MB LAX-DAG)
WOULD EXPECT THE LOW CLOUDS TO EXPAND OVER MOST COASTAL AREAS OVERNIGHT
AND SPREAD INTO MOST OF THE VALLEYS.
00Z ETA/NGM IN FAIRLY GOOD AGREEMENT WITH UPPER LEVEL FEATURES. THEY
BOTH MOVE AN UPPER TROF FROM THE GREAT BASIN NEWARD AND AWAY FROM CA
WHILE AT THE SAME TIME INCREASE 500 MB HEIGHTS INTO SOCAL AS AN UPPER
RIDGE BUILDS OVER NORTHERN MEXICO OR THE SRN ROCKIES. ETA STRONGER AND
FARTHER W WITH THE UPPER RIDGE. AT THE SAME TIME...AN UPPER LOW IS
FORECAST TO DEVELOP OFF THE SOCAL COAST. ETA WEAKER THAN NGM WITH THIS
FEATURE. THE 00Z NGM MATCHES BETTER WITH THE 12Z AVN VALID SUN
AFTERNOON. AT ANY RATE...BOTH THE ETA AND NGM ARE ADVERTISING
INCREASING THICKNESSES...ALONG WITH INCREASING TEMPS IN THE BOUNDARY
LAYER AND AT 850 MB. ALREADY SOME EASTERLY WINDS SHOWING UP IN THE
SOUNDINGS AROUND 4000 TO 7000 FEET. THE MODELS INDICATE SOME E AND SE
WINDS AT 850 MB THRU SUN. ALL INDICATIONS ARE FOR SHRINKING MARINE
LAYER THRU SUN ALONG WITH A WARMING TREND MOST AREAS.
WILL UPDATE THE ZONES BY 930 PM MAINLY TO CLEAN UP THE WORDING IN
THE FIRST PERIOD AND TO REFLECT WHAT IS HAPPENING WITH THE LOW CLOUDS
THIS EVENING. OTHERWISE...TEMPS THRU THE FCST PERIOD LOOK GOOD.
IN THE EXTENDED...IT APPEARS THE RELATIVELY WEAK UPPER LOW WILL BE OFF
THE SOCAL COAST MON THEN EDGE INLAND BY WED. HEIGHTS/THICKNESSES WITH
THE UPPER LOW SHOULD REMAIN RATHER HI DURING THE PERIOD. EVEN THO THE
UPPER LOW MAY HELP TO KICK UP AN EDDY...THE MRF SUGGESTS W TO E
GRADIENTS FROM THE COAST TO THE DESERTS SHOULD BE WEAK. TEMPS SHOULD
WIND UP TO BE NEAR NORMAL MOST AREAS DURING THE PERIOD. DRY CONDITIONS
ARE EXPECTED TO CONTINUE AS WELL AS THE MONSOONAL MOISTURE SHOULD
REMAIN CUT OFF FROM SOCAL.
LAX 0000. SIRARD.
.LAX...NONE.