000
FXUS66 KMTR 172152
AFDMTR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA
252 PM PDT FRI MAY 17 2013

.DISCUSSION...AS OF 02:45 PM PDT FRIDAY...CLOUDS HAVE ALMOST
ENTIRELY CLEARED FROM THE AREA THIS AFTERNOON...EXCEPTING A FEW
CU POP UPS ALONG THE SOUTHERN MOUNTAINS. TEMPS ARE RUNNING A
COUPLE OF DEGREES COOLER THAN YESTERDAY AND HIGHS ARE EXPECTED TO
STAY JUST SHY OF NORMAL.

A RIDGE WILL BUILD OVER THE EASTERN PACIFIC THIS WEEKEND CAUSING A
GRADUAL WARMING TREND THROUGH MONDAY. HIGH PRESSURE WILL KEEP
COASTAL LOW CLOUDS AROUND HOWEVER THE MARINE LAYER WILL BE
RELATIVELY SHALLOW AND THUS STRATUS WILL NOT GO VERY FAR INLAND.

A SHORTWAVE SLIDES SOUTH INTO THE GREAT BASIN SUNDAY INTO MONDAY
STRENGTHENING SURFACE PRESSURE GRADIENTS. THIS WILL CAUSE WINDS TO
INCREASE...ESPECIALLY OVER THE NORTH BAY MOUNTAINS...AND TURN
NORTHERLY AND THUS SLIGHTLY OFFSHORE. 925 WINDS REACH 20 TO 30 KT
OVER NAPA COUNTY BY EARLY MONDAY. THIS IS A POTENTIAL FIRE WEATHER
CONCERN...HOWEVER THE EVENT LOOKS TO BE SHORT IN DURATION AND NEAR
SURFACE WINDS NOT TERRIBLY STRONG. THE OFFSHORE WINDS WILL CAUSE
THE WARMER TEMPERATURES TO REACH FURTHER TOWARD THE COAST BEFORE A
QUICK RETURN TO ONSHORE FLOW BY MONDAY AFTERNOON. TEMPERATURES
RISE INTO THE 70S ALONG THE COAST TO LOWER 90S INLAND SUNDAY AND
MONDAY.

THE WARMING TREND IS SHORT LIVED HOWEVER AS AN UPPER LOW DROPS
SOUTHWARD FROM THE SUB ARCTIC THROUGH THE WEEK. THE MODELS SHOW
LESS DIVERGENCE TODAY WITH BOTH GFS AND ECMWF DETERMINISTIC RUNS
AND ENSEMBLE MEANS KEEPING THE LOW CENTER IN THE PACIFIC NORTHWEST
THROUGH THE END OF THE WEEK RATHER THAN GOING FURTHER SOUTH INTO
CALIFORNIA. THIS WOULD LIKELY KEEP ANY RAIN CHANCES CONFINED TO
THE NORTH BAY IF ANYWHERE IN THE CWA. REGARDLESS SFC TEMPS SINK BACK
TOWARD NORMAL OR SLIGHTLY BELOW BY THE END OF THE WEEK.

BY MEMORIAL DAY WEEKEND THE 12Z ECMWF DEPICTS THE LOW LIFTING
NORTH WHICH WOULD START TO WARM TEMPERATURES BACK UP. HOWEVER THE
DETERMINISTIC GFS AND ENSEMBLE MEANS OF BOTH SUGGEST CONTINUED
PRESENCE OF A TROUGH.

&&

.AVIATION...AS OF 10:40 AM PDT FRIDAY...CURRENT SATELLITE PICS
SHOW STRATUS BANKED UP ON THE WESTERN SIDE OF THE COASTAL
MOUNTAINS AND MAJOR TERMINALS REMAIN CLEAR. WITH A WESTERLY
FLOW...THERE SHOULD BE AN EARLY RETURN OF LOWER CLOUDS AND REDUCED
CIGS THIS EVENING AFTER 02-04Z. MVFR-IFR CIGS EXPECTED AT ALL
TERMINALS OVERNIGHT WITH LOW CLOUDS...BURNING OFF BY 14-17Z SAT AT
ALL TERMINALS WITH PERSISTENT WESTERLY FLOW.

VICINITY OF KSFO...VFR CONDITIONS SHOULD PERSIST THROUGH 03Z SAT WITH
AN EARLY RETURN OF LOW CLOUDS GIVEN THE WEST WINDS. MVFR CIGS
EXPECTED OVERNIGHT WITH BURN OFF AROUND 16Z SAT. WEST WINDS
INCREASING TO AROUND 20 KTS WITH GUSTS TO 27 KTS 21Z FRI-03Z SAT.

KSFO BRIDGE APPROACH...CIGS WILL LOWER IN THE VICINITY OF KSFO
FIRST AFTER 00Z THIS EVENING AND SPREAD SOUTH TO APPROACH.

MONTEREY BAY AREA TERMINALS...MVFR CIGS WILL RETURN AFTER 02Z SAT
AND PERSIST THROUGH 15-17Z SAT. WEST WINDS AROUND 10-15 KTS THROUGH
00Z SAT THEN DECREASING.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .TNGT...SCA...PT REYES TO PIGEON PT 0-10 NM FROM 9 PM
             SCA...PIGEON PT TO PT PINOS 0-10 NM FROM 9 PM
             SCA...PT ARENA TO PIGEON PT 10-60 NM FROM 9 PM
             SCA...PIGEON PT TO PT PIEDRAS BLANCAS 10-60 NM FROM 9 PM
             SCA...PT ARENA TO PT REYES 0-10 NM
             SCA...PT PINOS TO PT PIEDRAS BLANCAS 0-10 NM
             SCA...SF BAY UNTIL 9 PM
             SCA...MRY BAY UNTIL 9 PM

&&

$$

PUBLIC FORECAST: AC
AVIATION/MARINE: JOHNSON

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