699  
FXUS66 KMTR 181640  
AFDMTR  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA  
940 AM PDT SUN AUG 18 2019  
   
SYNOPSIS
 
COOLER TEMPERATURES WILL PREVAIL ACROSS THE REGION  
TODAY, WITH SEASONABLE CONDITIONS CONTINUING THROUGH THE FIRST  
PART OF THE WORK WEEK. A GRADUAL WARMING TREND WILL DEVELOP BY  
WEDNESDAY AND CONTINUE THROUGH NEXT WEEKEND AS HIGHER PRESSURE  
SETS UP OVER NORTHERN CALIFORNIA.  
 

 
   
DISCUSSION...AS OF 09:40 AM PDT SUNDAY
 
WATER VAPOR IMAGERY  
SHOWS A TROUGH OF LOW PRESSURE ALONG THE WEST COAST THIS MORNING,  
WITH A WEAK DISTURBANCE MOVING INLAND ACROSS NORTHERN CALIFORNIA.  
THIS DISTURBANCE HELPED DEEPEN THE MARINE LAYER OVERNIGHT TO  
AROUND 3000 FEET, ACCORDING TO THE FORT ORD PROFILER. THIS  
DEEPENING ALONG WITH THE UPSLOPE FLOW INTO THE COASTAL MOUNTAINS  
IS ALLOWING FOR SOME DRIZZLE TO DEVELOP. ALTHOUGH THE REPORTS ARE  
PRETTY HIT AND MISS, A SPOTTER FROM LIVE OAK CALLED IN TO REPORT  
THAT THE DRIZZLE WAS ACCUMULATING. IN FACT, IT SEEMS LIKE THE  
SANTA CRUZ MOUNTAINS AND COASTAL AREAS ARE THE BIG WINNER, WITH  
OBSERVATIONS SHOWING BETWEEN 0.01 AND 0.06 INCHES. EXPECT THIS  
DRIZZLE TO CONTINUE THROUGH LATE THIS MORNING, BEFORE WINDING DOWN  
THIS AFTERNOON. OTHERWISE, THE MAIN FORECAST CONCERN FOR TODAY  
WILL BE WITH THE COOLER CONDITIONS ACROSS THE REGION. AT THIS  
TIME, THE FORECAST SHOWS THIS TREND, AND NO UPDATES ARE PLANNED AT  
THIS TIME. WILL NEED TO WATCH THE INLAND AREAS THOUGH, AS THEY  
MAY NOT GET QUITE AS WARM AS THE CURRENT FORECAST REFLECTS.  
 
THIS UPPER LEVEL TROUGH WILL REMAIN ALONG THE WEST COAST THROUGH  
THE FIRST PART OF THE WORK WEEK, WITH A SECONDARY WEAK DISTURBANCE  
FORECAST TO MOVE INLAND DURING THE DAY ON MONDAY. THEREFORE,  
EXPECT THE MARINE LAYER TO REMAIN ON THE DEEP SIDE TONIGHT, WITH  
ANOTHER GOOD INLAND PUSH TONIGHT. TEMPERATURES BEING SIMILAR TO  
TODAY OR SLIGHTLY COOLER DEPENDING ON LOCATION, BUT BE WITHIN  
SEASONAL NORMS. A GRADUAL WARMING TREND WILL THEN DEVELOP FOR  
MIDWEEK AND NEXT WEEKEND, AS HIGH PRESSURE SLOWLY BUILDS BACK INTO  
THE REGION. PALMER  
 

 
   
PREVIOUS DISCUSSION
 
/ISSUED AT 03:03 AM PDT SUNDAY/  
THE LONG WAVE TROUGH OVER THE BAY AREA DEEPENS TONIGHT AND INTO  
TOMORROW. THE FORT ORD PROFILER ALREADY HAS A MARINE LAYER  
APPROXIMATED AT OVER 3000 FEET AS LOW CLOUDS ARE SEEN ON SATELLITE  
OVER THE SANTA CRUZ MOUNTAINS AND MONTEREY BAY, DOWN THE SALINAS  
VALLEY AND MAKING ITS WAY FURTHER INLAND. SMALL CHANCES OF PATCHY  
DRIZZLE ARE EXPECTED FOR THE COASTS OF SAN MATEO AND SANTA CRUZ  
COUNTIES AS WELL AS ISOLATED AREAS ALONG THE BIG SUR COAST THROUGH  
MID-MORNING AS LOW LEVEL ONSHORE FLOW PERSISTS. CLOUDS SHOULD  
CLEAR FOR MOST INLAND AREAS BY THE AFTERNOON ON SUNDAY, BUT SOME  
COASTAL AREAS WILL MOST LIKELY SEE CLOUDS REMAIN ALL DAY. THE  
DEEPENING TROUGH SUNDAY, WITH THE AIDE OF A DEEPER MARINE LAYER  
AND PERSISTENT ONSHORE FLOW, WILL SEE COOLER TEMPERATURES ONCE  
AGAIN AROUND THE BAY AREA. THOUGH IT WILL BE A SMALLER COOLING  
COMPARED TO WHAT WAS EXPERIENCED SATURDAY, INTERIOR LOCATIONS ARE  
EXPECTED TO SEE THE MOST COOL DOWN DUE TO THE INLAND EXTENT OF THE  
ONSHORE FLOW.  
 
BY MONDAY AND INTO TUESDAY, HIGH PRESSURE BEGINS TO REBUILD OVER  
CENTRAL TEXAS. TEMPERATURES AROUND THE BAY AREA WILL SLOWLY INCREASE  
AS THE UPPER RIDGE OVER THE SOUTHERN PLAINS SHIFTS WESTWARD, RAISING  
HEIGHTS OVER CALIFORNIA. MORE ROBUST WARMING IS FORECAST BY MID-TO-  
END OF WEEK. THIS WARM-UP WILL NOT BE OF THE SAME MAGNITUDE AS THIS  
PREVIOUS WEEK'S HEAR, DUE TO AN APPROACHING TROUGH FROM THE WEST.  
LONGER RANGE MODELS SHOW THAT BY NEXT WEEKEND, A RIDGE BUILDS OFF  
THE COAST OF NORTHERN CALIFORNIA. THIS WILL BE THE NEXT OPPORTUNITY  
TO BRING POTENTIALLY SIGNIFICANT HEATING TO THE BAY AREA BUT ALSO  
THE CHANGE OF ONSHORE FLOW TO OFFSHORE.  
 

 
   
AVIATION...AS OF 5:05 AM PDT SUNDAY
 
NEARLY CONTINUOUS LOW  
CLOUDS /MVFR/ EXTENDS NORTHWARD FROM THE CENTRAL COAST TO THE  
SANTA CRUZ MOUNTAINS AND NORTHWARD TO COASTAL SONOMA COUNTY AND IS  
ADVANCING INTO THE SOUTH BAY; 2.9 MB SMX-SFO AND 2.4 MB SNS-SJC  
PRESSURE GRADIENTS ARE FORECAST TO WANE TODAY ALLOWING AN  
AFTERNOON AND EVENING 3 MB SFO-SAC ONSHORE GRADIENT AND WIND TO  
PREVAIL LATER TODAY AND AGAIN LATER MONDAY. LOW CLOUDS /MVFR/  
CONTINUE TO FILL IN OVER THE NORTH BAY VALLEYS. PATCHY MVFR  
CEILINGS ARE OTHERWISE FOUND OVER THE BAY AREA WHILE WELL INLAND  
IT'S VFR. THE WEATHER TODAY INTO MONDAY IS DRIVEN BY COOLING AND A  
DEEPENING MARINE LAYER, PATCHY MORNING COASTAL DRIZZLE IS ALSO  
POSSIBLE. GUSTY SW WINDS STILL REPORTED AT PACHECO PASS NORTHWARD  
TO A FEW LOCATIONS IN THE EAST BAY, OTHERWISE LIGHTER WINDS ALL  
LOCATIONS. WHERE GUSTY WINDS LINGER THEY SHOULD DIMINISH THIS  
MORNING AS THE SOUTH TO NORTH SURFACE PRESSURE PATTERN OVER NORCAL  
BECOMES MUCH MORE BALANCED AND FLAT, ONSHORE WINDS BECOMING THE  
PRIMARY FOCUS TODAY THROUGH MONDAY.  
 
VICINITY OF KSFO...VFR, SOUTH WIND 5 TO 10 KNOTS SHIFTING OVER SW  
THEN W BY LATE MORNING OR EARLY AFTERNOON AND INCREASING TO NEAR  
15 KNOTS. LIGHTER WIND TONIGHT AND MONDAY MORNING.  
 
SFO BRIDGE APPROACH...SIMILAR TO KSFO.  
 
MONTEREY BAY TERMINALS...MVFR CEILINGS WITH LIGHT WINDS AND PATCHY  
DRIZZLE IN THE MORNING, VFR BY LATE MORNING OR EARLY AFTERNOON AND  
ONSHORE WINDS 10 TO 15 KNOTS. LOW CLOUDS /MVFR/ RETURNS THIS EVENING  
WITH MVFR TONIGHT INTO MONDAY MORNING.  
 

 
   
MARINE...AS OF 8:47 AM PDT SUNDAY
 
WINDS WILL DIMINISH THROUGH  
MID WEEK AS HIGH PRESSURE WEAKENS OFF THE CALIFORNIA COAST AND A  
LOW PRESSURE SYSTEM DEVELOPS OFF OF BRITISH COLUMBIA. SHORTER  
PERIOD NORTHWEST WAVES AT AROUND 8 TO 10 SECONDS WILL CONTINUE TO  
BE THE DOMINATE FEATURE THROUGH MUCH OF THE WEEK ALONG WITH A  
LIGHT SOUTHERLY SWELL.  
 

 
   
MTR WATCHES/WARNINGS/ADVISORIES
 
 
.TDAY...SCA...PT ARENA TO PIGEON PT 10-60 NM UNTIL 9 AM  
 

 
 

 
 
PUBLIC FORECAST: PALMER / DK  
AVIATION: CANEPA  
MARINE: AS  
 
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