875  
FXUS66 KMTR 200532  
AFDMTR  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA  
1032 PM PDT WED JUN 19 2019  
   
SYNOPSIS
 
SLIGHTLY COOLER TEMPERATURES ARE EXPECTED ONCE AGAIN  
ON THURSDAY. WINDS SHIFT TO THE NORTH ON FRIDAY AND SATURDAY WHICH  
WILL ALLOW FOR SLIGHTLY WARMER TEMPERATURES LEADING INTO THE  
WEEKEND. THESE NORTHERLY WINDS HAVE THE POTENTIAL TO BE GUSTY  
PARTICULARLY IN THE NORTH BAY HILLS FRIDAY AND SATURDAY MORNINGS.  
 

 
   
DISCUSSION...AS OF 08:03 PM PDT WEDNESDAY
 
THE MARINE LAYER IS  
TRICKLING INTO LOW LYING VALLEYS THIS EVENING AS IT COMPRESSES  
DOWN TO A MODEST 1000FT AGL. IT WILL RETREAT ONCE AGAIN TO THE  
COASTLINE TOMORROW AFTERNOON. THE EASTERN PACIFIC RIDGE IS  
EXPECTED TO CONTINUE TO ERODE AS A TROUGH DESCENDS FROM THE  
PACIFIC NORTHWEST TOMORROW AND INTO FRIDAY. THE BAY AREA WILL  
REMAIN ON THE WEST SIDE OF THE TROUGH WHICH WILL KEEP SKIES MOSTLY  
CLEAR, PROVIDING PLENTY OF SUNSHINE AND DRIER CONDITIONS. THIS  
TROUGH WILL BRING NORTHERLY WINDS THAT WILL BE GUSTY, 30 MPH OR  
MORE, PARTICULARLY IN HIGHER ELEVATIONS OF THE NORTH BAY ON  
FRIDAY AND SATURDAY MORNING. THESE DOWNSLOPING WINDS WILL HELP  
BRING WARMER TEMPERATURES TO THE BAY AREA FRIDAY AND INTO THE  
WEEKEND. EXTENDED MODELS ARE SHOWING THE RETURN OF ONSHORE FLOW  
AND A DEEPER MARINE LAYER EARLY NEXT WEEK WHICH WILL IN TURN BRING  
COOLER TEMPERATURES.  
 

 
   
PREV DISCUSSION...AS OF 1:48 PM PDT WEDNESDAY
 
SATELLITE IMAGERY  
SHOWS LOW CLOUDS HAVE MOSTLY CLEARED TO THE COAST ACROSS THE  
DISTRICT. THERE IS STILL SOME STRATUS AROUND THE MONTEREY BAY,  
NEAR HALF MOON BAY, OVER PORTIONS OF SAN FRANCISCO, AND ALONG THE  
SONOMA COUNTY COAST. CURRENT TEMPERATURE READINGS ARE RUNNING  
COOLER THAN YESTERDAY AT THIS TIME WITH 60S TO LOWER 80S BEING  
REPORTED AT AREA AIRPORTS. LOCATIONS IN THE SOUTHERN INTERIOR HAVE  
WARMED INTO THE UPPER 80S AND LOWER 90S. THE MARINE LAYER HAS  
INCREASED TO AROUND 2000 FEET AS OF NOON, AND THE ONSHORE SURFACE  
PRESSURE GRADIENT IS A HEALTHY 2.9 MB, SO EXPECT LOW CLOUDS TO  
SPREAD INLAND AGAIN OVERNIGHT.  
 
AN UPPER LEVEL LOW DROPPING SOUTH FROM WESTERN CANADA INTO THE  
PACIFIC NORTHWEST WILL AID IN CONTINUED COOLING OVER THE NEXT  
COUPLE OF DAYS. THURSDAY WILL BE THE COOLEST DAY AS AN UPPER LEVEL  
DISTURBANCE MOVES SOUTH ACROSS NEVADA WITH THE TROUGH AXIS MOVING  
THROUGH OUR DISTRICT. THIS DISTURBANCE WILL TIGHTEN AN OFFSHORE  
SURFACE PRESSURE GRADIENT WITH NORTH TO NORTHEAST WINDS INCREASING  
THURSDAY NIGHT AS THIS TROUGH MOVES THROUGH. THE LATEST RUN OF  
THE NAM12 MODEL STILL SHOWS 925 MB WINDS IN THE 25 TO 35 KT  
RANGE...STRONGEST OVER THE HIGHER TERRAIN IN NAPA COUNTY. AFTER  
WEAKENING DURING THE DAY FRIDAY THE NORTH TO NORTHEAST WINDS WILL  
RAMP UP ONCE AGAIN FRIDAY NIGHT, ALTHOUGH WEAKER THAN THURSDAY  
NIGHT. CURRENTLY THERE ARE NO WATCHES OR ADVISORIES FOR THE NORTH  
AND EAST BAY HILLS BUT WILL CONTINUE TO MONITOR.  
 
LONGER RANGE MODELS INDICATE A LONG-WAVE UPPER TROUGH OVER THE  
EASTERN PACIFIC, WITH HIGH PRESSURE OVER THE ROCKY MOUNTAIN  
STATES. THIS WILL MAINTAIN COOL TO NEAR SEASONALLY NORMAL TEMPS  
NEXT WEEK.  
 

 
   
AVIATION...AS OF 10:32 PM PDT WEDNESDAY
 
FOR 06Z TAFS. THE  
MARINE LAYER HAS REBOUNDED TO OVER 2000 FT AGL PER THE FORT ORD  
PROFILER. SATELLITE IMAGERY SHOWS LOW CLOUDS HAVE BEGUN TO MOVE  
INLAND AND DOWN THE VALLEYS. CONDITIONS RANGE FROM VFR AT KSJC AND  
KLVK TO IFR AT KSTS, KOAK, KMRY AND KSNS. EXPECT STRATUS TO  
CONTINUE TO EXPAND OVERNIGHT WITH MVFR/IFR CONDITIONS TO PREVAIL  
THROUGH TOMORROW MORNING. RIGHT NOW EXPECTING CLEARING GENERALLY  
BETWEEN 17Z-19Z TOMORROW FOR MOST LOCATIONS. WINDS WILL CONTINUE  
TO DIMINISH OVERNIGHT BEFORE INCREASING AND TURNING ONSHORE AGAIN  
TOMORROW AFTERNOON.  
 
VICINITY OF KSFO...SATELLITE SHOWS STRATUS SLOWLY CLOSING IN ON  
THE TERMINAL. MVFR/IFR CIGS EXPECTED TO DEVELOP OVER THE NEXT  
COUPLE OF HOURS AND THEN CONTINUE INTO LATE TOMORROW MORNING  
(~17Z-19Z). WINDS WILL REMAIN LIGHT OVERNIGHT BEFORE ONSHORE  
WINDS INCREASE TOMORROW AFTERNOON.  
 
SFO BRIDGE APPROACH...PATCHES OF STRATUS HAVE DEVELOPED AROUND THE  
BRIDGE. THE APPROACH MAY LOSE VISUALS BEFORE THE TERMINAL THIS  
EVENING, OTHERWISE SIMILAR TO SFO.  
 
MONTEREY BAY TERMINALS...IFR CIGS HAVE SETTLED IN FOR THE EVENING.  
LIFR CONDITIONS MAY DEVELOP OVERNIGHT. LATEST GUIDANCE CONTINUES  
TO SHOW STRATUS HANGING AROUND THE PENINSULA FOR MOST OF THE DAY  
TOMORROW. IT IS POSSIBLE THAT MVFR/IFR CIGS CONTINUE AT KMRY ALL  
DAY TOMORROW, BUT CONFIDENCE IS LOW. GENERALLY LIGHT WINDS  
OVERNIGHT.  
 

 
   
MARINE...AS OF 08:45 PM PDT WEDNESDAY
 
LIGHT SOUTHERLY WINDS  
WILL PERSIST ALONG THE COAST SOUTH OF POINT REYES THROUGH TOMORROW  
AS NORTHERLY WINDS INCREASE ACROSS THE NORTHERN OUTER WATERS  
TONIGHT. GALE FORCE GUSTS WILL BE POSSIBLE STARTING TONIGHT OVER  
THE OUTER WATERS NORTH OF POINT REYES THROUGH AT LEAST TOMORROW  
NIGHT. ELEVATED WINDS WILL BECOME MORE WIDESPREAD, MAINLY OVER THE  
OUTER WATERS, TOMORROW THROUGH FRIDAY. THESE WINDS WILL RESULT IN  
STEEP FRESH SWELL CREATING HAZARDOUS SEAS CONDITIONS, ESPECIALLY  
FOR SMALLER VESSELS.  
 

 
   
MTR WATCHES/WARNINGS/ADVISORIES
 
 
.TNGT...GLW...PT ARENA TO PIGEON PT 10-60 NM  
SCA...PT ARENA TO PT REYES 0-10 NM FROM 3 AM  
 

 
 

 
 
PUBLIC FORECAST: DK  
AVIATION: AS  
MARINE: AS  
 
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