430  
FXUS66 KMTR 300552  
AFDMTR  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA  
1052 PM PDT WED MAR 29 2017  
   
SYNOPSIS
 
COOLER AND BREEZY CONDITIONS ARE FORECAST FOR  
THURSDAY AFTER A COLD FRONT SWEEPS THROUGH THE REGION. THIS  
SYSTEM MAY PRODUCE ISOLATED LIGHT SHOWERS FROM LATE TONIGHT INTO  
EARLY THURSDAY MORNING, HOWEVER MOST LOCATIONS WILL NOT RECEIVE  
MEASURABLE RAINFALL. LOCALLY STRONG AND GUSTY NORTHWEST WINDS ARE  
LIKELY FROM THURSDAY AFTERNOON INTO FRIDAY. A WARMING TREND IS  
THEN EXPECTED FOR THE UPCOMING WEEKEND AS HIGH PRESSURE REBUILDS  
OVER THE REGION.  
 

 
   
DISCUSSION...AS OF 9:05 PM PDT WEDNESDAY
 
EVENING SATELLITE  
IMAGERY SHOWS A COLD FRONT MOVING THROUGH NORTHWEST CALIFORNIA.  
CLOUDS HAVE BEGUN TO INCREASE OVER OUR AREA IN ADVANCE OF THE COLD  
FRONT - MOSTLY HIGH CLOUDS BUT ALSO PATCHY LOW CLOUDS IN COASTAL  
AREAS. THIS COLD FRONT IS EXPECTED TO SWEEP SOUTHEAST AND THROUGH  
OUR AREA LATE TONIGHT AND EARLY THURSDAY MORNING. MODELS CONTINUE  
TO INDICATE THAT MOST PRECIPITATION WITH THIS SYSTEM WILL FALL TO  
OUR NORTH AND EAST. HOWEVER, THE 00Z NAM CONTINUES TO SHOW WIDELY  
SCATTERED LIGHT PRECIPITATION ACROSS OUR AREA STARTING AROUND  
MIDNIGHT TONIGHT AND CONTINUING UNTIL SHORTLY AFTER SUNRISE FRIDAY  
MORNING. MOST OTHER MODELS ALSO INDICATE AT LEAST A SLIGHT CHANCE  
OF PRECIPITATION. IN ANY EVENT, WHERE RAIN DOES FALL, AMOUNTS ARE  
EXPECTED TO BE VERY LIGHT. A COOLER AIRMASS WILL ARRIVE BEHIND  
THE INCOMING COLD FRONT AND HIGH TEMPERATURES ON THURSDAY ARE  
EXPECTED TO BE 5 TO 10 DEGREES COOLER THAN TODAY.  
 
THE PRIMARY WEATHER IMPACT FROM THIS SYSTEM WILL BE LOCALLY STRONG  
AND GUSTY NORTHERLY WINDS IN THE POST-FRONTAL ENVIRONMENT STARTING  
TOMORROW. NW-SE SURFACE PRESSURE GRADIENTS ARE EXPECTED TO  
QUICKLY STEEPEN ON THURSDAY AS HIGH PRESSURE BUILDS OFF THE  
NORTHERN CALIFORNIA COAST AND LOW PRESSURE DEEPENS OVER FAR  
SOUTHERN CALIFORNIA AND NEVADA. INITIALLY, ON THURSDAY, STRONGEST  
NORTHWEST WINDS WILL OCCUR ALONG THE COAST. COASTAL WINDS ARE  
EXPECTED TO INCREASE IN THE MORNING BUT NOT REACH THEIR PEAK  
INTENSITY UNTIL LATE THURSDAY AFTERNOON AND EARLY THURSDAY  
EVENING. COASTAL WINDS WILL THEN SUBSIDE BY LATE THURSDAY  
EVENING. BUT AS WINDS DECREASE NEAR THE COAST, NORTH WINDS ARE  
EXPECTED TO INCREASE IN THE HILLS AND BE LOCALLY STRONG AND GUSTY  
FROM LATE THURSDAY NIGHT THROUGH MIDDAY FRIDAY. A WIND ADVISORY  
HAS BEEN ISSUED FOR MOST COASTAL ZONES FROM NOON THROUGH 8 PM  
THURSDAY AND FOR MOST MOUNTAIN ZONES FROM MIDNIGHT THURSDAY NIGHT  
THROUGH MIDDAY FRIDAY. LOCAL WIND GUSTS UP TO 45 MPH ARE LIKELY  
NEAR THE COAST LATE THURSDAY, AND WINDS GUSTS UP TO 50 MPH ARE  
EXPECTED IN THE HILLS BY LATE THURSDAY NIGHT. WINDS WILL SUBSIDE  
GRADUALLY THROUGH FRIDAY AND FRIDAY NIGHT, BUT LOCALLY BREEZY  
CONDITIONS ARE EXPECTED TO CONTINUE INTO SATURDAY MORNING, MAINLY  
IN THE HILLS.  
 
THESE NORTHERLY WINDS WILL BRING A MUCH DRIER AIRMASS INTO OUR  
REGION BY FRIDAY. THE DRY AIRMASS WILL MEAN COOL TEMPERATURES IN  
THE VALLEYS TO START THE DAY FRIDAY, BUT ALSO A QUICK WARMUP ONCE  
THE SUN RISES. AN UPPER RIDGE WILL THEN BUILD OVER CALIFORNIA BY  
SATURDAY, ALLOWING TEMPERATURES TO WARM SEVERAL DEGREES BY THE  
WEEKEND. OUR WEEKEND IS SHAPING UP TO BE DRY WITH SEASONABLY WARM  
TEMPERATURES.  
 
TEMPERATURES WILL COOL EARLY NEXT WEEK ANOTHER SYSTEM DROPS IN  
FROM THE NORTHWEST. THE MONDAY SYSTEM LOOKS LESS LIKELY TO  
PRODUCE ANY PRECIPITATION IN OUR AREA, BUT WILL RESULT IN BREEZY  
CONDITIONS ONCE AGAIN BY MONDAY AFTERNOON.  
 
FROM PREVIOUS DISCUSSION...THE LONGER RANGE GUIDANCE CONTINUES TO  
SHOW A RETURN TO WET WEATHER CONDITIONS BY LATE NEXT WEEK. THE  
MODELS GENERALLY AGREE THAT A MORE POTENT WEATHER SYSTEM WILL DROP  
SOUTHWARD INTO NORTHERN CALIFORNIA BY THURSDAY OR FRIDAY OF NEXT  
WEEK WITH A MODERATE MOISTURE TAP. BOTH THE GFS AND ECMWF SHOW  
WIDESPREAD RAINFALL ACROSS THE REGION BY NEXT FRIDAY. HOWEVER,  
BEING MORE THAN A WEEK OUT, CONFIDENCE REMAINS LOW AT THIS TIME  
AND CHANGES TO THE FORECAST ARE LIKELY.  
 

 
   
AVIATION...AS OF 10:52 PM PDT WEDNESDAY
 
COASTAL STRATUS AND  
FOG WITH A COMBINATION OF IFR AND MVFR CIGS REPORTED THIS EVENING.  
PRIMARILY EXPECTING AN ONSHORE WIND FLOW TONIGHT ALONG WITH  
POCKETS OF LIGHT RAIN OR DRIZZLE DEVELOPING. A COLD FRONT MOVES  
THROUGH LATE TONIGHT AND THURSDAY MORNING FIRST LIFTING THEN  
EVENTUALLY ERODING THE MARINE INVERSION FOLLOWED BY A STEEPENING  
NORTHERLY GRADIENT AND WINDS THURSDAY INTO FRIDAY. VFR IS LIKELY  
TO RETURN BY MID-LATE THURSDAY MORNING, STRONG AND GUSTY NW WINDS  
COASTAL WATERS WITH SOME OVERLAP ONTO LAND DEVELOPING THURSDAY  
AFTERNOON AND EVENING.  
 
VICINITY OF KSFO...MVFR CIG DEVELOPING TONIGHT THEN LOWERING TO  
IFR CIG IN LIGHT DRIZZLE OR RAIN TONIGHT WITH W-NW WINDS. CLEARING  
TO VFR BY 17Z THURSDAY, STRONG AND GUSTY W-NW WINDS THURSDAY  
AFTERNOON AND EVENING.  
 
SFO BRIDGE APPROACH...SIMILAR TO KSFO.  
 
MONTEREY BAY TERMINALS...MVFR/IFR DEVELOPING TONIGHT WITH LIGHT  
DRIZZLE OR RAIN DEVELOPING LATER TONIGHT INTO THURSDAY MORNING.  
VFR FORECAST TO RETURN BY LATE THURSDAY MORNING, STRONG AND GUSTY  
W-NW WINDS THURSDAY AFTERNOON AND EVENING.  
 

 
   
MARINE...AS OF 10:29 PM PDT WEDNESDAY
 
GUSTY NORTHWEST WINDS  
WILL ACCOMPANY A COLD FRONTAL PASSAGE LATER TONIGHT THROUGH  
THURSDAY MORNING. SURFACE HIGH PRESSURE WILL BUILD OVER FAR  
NORTHERN CALIFORNIA THURSDAY INTO FRIDAY RESULTING IN GALE FORCE  
WINDS OVER THE COASTAL WATERS BEGINNING LATER THURSDAY AND CONTINUING  
INTO FRIDAY. NORTHWEST SWELL WILL LEVEL OFF WHILE SWELL PERIODS  
STEADILY DECREASE TONIGHT THROUGH THURSDAY. LARGE VERY LONG PERIOD  
NORTHWESTERLY SWELL WILL MOVE INTO THE COASTAL WATERS SATURDAY  
EVENING INTO SUNDAY.  
 

 
   
MTR WATCHES/WARNINGS/ADVISORIES
 
 
.TNGT...SCA...PT ARENA TO PT REYES 0-10 NM  
SCA...PT REYES TO PIGEON PT 0-10 NM  
SCA...PIGEON PT TO PT PINOS 0-10 NM  
SCA...PT PINOS TO PT PIEDRAS BLANCAS 0-10 NM  
SCA...PT ARENA TO PIGEON PT 10-60 NM  
SCA...PIGEON PT TO PT PIEDRAS BLANCAS 10-60 NM  
SCA...ROUGH BAR ADVISORY FOR SF BAR  
SCA...MRY BAY UNTIL 3 AM  
 

 
 

 
 
PUBLIC FORECAST: DYKEMA/RGASS  
AVIATION/MARINE: CANEPA  
 
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