Area Forecast Discussion
Issued by NWS San Francisco Bay Area, CA

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000
FXUS66 KMTR 211158
AFDMTR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA
458 AM PDT TUE APR 21 2015

.SYNOPSIS...WEATHER CONDITIONS OVER THE REGION TODAY WILL BE A
NEAR REPEAT OF THOSE ON MONDAY WITH A DEEP MARINE LAYER IN PLACE.
A SLIGHT INLAND COOLING TREND IS THEN EXPECTED THROUGH LATE WEEK
AS WEAK UPPER LEVEL DISTURBANCES MOVE THROUGH THE STATE. THESE
WEAK WEATHER SYSTEMS WILL RESULT IN A SLIGHT CHANCE OF SHOWERS AT
TIMES THROUGH THE REMAINDER OF THE WEEK...PRIMARILY OVER THE
MOUNTAINS.

&&

.DISCUSSION...AS OF 04:10 AM PDT TUESDAY...THE PRESENCE OF A
RELATIVELY DEEP MARINE LAYER ONCE AGAIN ALLOWED FOR LOW CLOUDS TO
DEVELOP WELL INLAND EARLY THIS MORNING. AS A
RESULT...TEMPERATURES ARE SIMILAR TO 24 HOURS AGO...GENERALLY IN
THE LOW/MID 50S. A WEAK UPPER LEVEL LOW REMAINS TO OUR SOUTH AND
WILL MOVE INTO SOUTHERN CALIFORNIA TODAY WHILE A MID/UPPER LEVEL
TROUGH APPROACHES THE PACIFIC NORTHWEST. WITH LITTLE CHANGE IN
THE OVERALL PATTERN ALOFT...WEATHER CONDITIONS WILL BE SIMILAR TO
THOSE YESTERDAY. WHILE INLAND AREAS ARE EXPECTED TO SEE CLEARING
BY LATE MORNING/EARLY AFTERNOON...MANY COASTAL LOCATIONS WILL
ONCE AGAIN REMAIN BENEATH LOW CLOUD COVER THROUGH MUCH OF THE
DAY. IN ADDITION...THE FORECAST MODELS CONTINUE TO SUGGEST THE
BEST CHANCES FOR CONVECTION TODAY WILL BE WELL INLAND OVER THE
HIGHER TERRAIN...WITH JUST AN OUTSIDE CHANCE OVER SOUTHERN
MONTEREY AND SAN BENITO COUNTIES.

THE APPROACHING TROUGH TO OUR NORTHWEST WILL PUSH INLAND OVER
NORTHERN CALIFORNIA THROUGH MIDWEEK AND BRING WITH IT A SLIGHTLY
COOLER AIRMASS. THIS TOO SHOULD HELP BREAK DOWN THE MARINE LAYER
TO SOME EXTENT BY WEDNESDAY...ESPECIALLY OVER THE NORTHERN HALF
OF THE REGION. MEANWHILE...THE NAM AND OTHER HIGHER RESOLUTION
MODELS MAINTAIN DEEP BOUNDARY LAYER MOISTURE ACROSS MUCH OF THE
CENTRAL COAST. REGARDLESS...DAYTIME TEMPERATURES WILL COOL TO
NEAR SEASONAL AVERAGES REGION-WIDE THROUGH LATE WEEK. WITH BROAD
MID/UPPER LEVEL TROUGHING FORECAST OVER THE STATE THROUGH LATE
WEEK...CANNOT RULE OUT A FEW SHOWERS OVER THE INLAND
HILLS/MOUNTAINS. YET MOST LOCATIONS WILL REMAIN DRY THROUGH THE
REMAINDER OF THE WORK WEEK.

A SHORT-WAVE DISTURBANCE IS THEN FORECAST TO SWEEP THROUGH ON
FRIDAY AS THE MAIN UPPER LEVEL TROUGH FINALLY SHIFTS INLAND. THIS
WILL COOL TEMPERATURES BY A FEW DEGREES FOR FRIDAY WITH ANOTHER
SLIGHT CHANCE OF SHOWERS OVER HIGHER ELEVATIONS ACROSS THE
CENTRAL COAST. OTHERWISE...THIS SYSTEM WILL LIKELY PASS ACROSS
THE REGION WITHOUT MUCH FANFARE.

THE MEDIUM RANGE FORECAST MODELS NOW GENERALLY AGREE IN WEAK
RIDGING OVER MUCH OF THE STATE THIS WEEKEND INTO EARLY NEXT WEEK.
AS A RESULT...WILL KEEP GENERALLY DRY CONDITIONS REGION-WIDE
ALONG WITH INLAND WARMING FOR MUCH OF THE UPCOMING WEEKEND. THE
NEXT MID/UPPER LEVEL SYSTEM IS THEN FORECAST TO PUSH INLAND TO
OUR NORTH SUNDAY INTO MONDAY...MAINLY ONLY IMPACTING THE PACIFIC
NORTHWEST AND NORTHERN CALIFORNIA. THUS...WILL MAINTAIN A DRY
FORECAST THROUGH THE EXTENDED.

&&

.AVIATION...AS OF 4:58 PM PDT TUESDAY...BORDERLINE IFR/MVFR CIGS
HAVE FILLED IN ACROSS AREA TERMINALS THIS MORNING. CLEARING TIME
IS EXPECTED TO BE SIMILAR TO MONDAY WITH LOW CLOUDS SCATTERING OUT
AROUND 19Z-20Z. LIGHT TO MODERATE SOUTHWEST WINDS WILL RAMP UP
THIS AFTERNOON TO AROUND 15 KT. MODERATELY HIGH CONFIDENCE.

VICINITY OF KSFO...BORDERLINE IFR/MVFR CIGS ARE ANTICIPATED TO
SCATTER OUT AROUND 20Z THIS AFTERNOON. WEST TO SOUTHWEST WINDS
AROUND 10 KT EXPECTED TO INCREASE TO AROUND 15 KT WITH THE ONSET
OF THE AFTERNOON SEA BREEZE. MODERATELY HIGH CONFIDENCE.

SFO BRIDGE APPROACH...SIMILAR TO KSFO.

MONTEREY BAY AREA TERMINALS...MVFR CIGS WILL PERSIST THROUGH THE
DAY TODAY. CIGS WILL LIFT TO AROUND 1500 FEET THIS AFTERNOON BUT
ARE NOT FORECAST TO CLEAR. WEST TO SOUTHWEST WINDS AROUND 5 KT
WILL INCREASE TO AROUND 10 KT THIS AFTERNOON.

&&

.MARINE...AS OF 04:28 AM PDT TUESDAY...STRONG NORTHWESTERLY WINDS
ARE EXPECTED TODAY ACROSS THE COASTAL WATERS AS HIGH PRESSURE
BUILDS OVER THE EASTERN PACIFIC. WATERS NORTH OF POINT REYES WILL
SEE THE STRONGEST WINDS WITH GALE WARNINGS IN PLACE FOR LATE THIS
AFTERNOON. SEAS WILL RAPIDLY BUILD ON TODAY IN RESPONSE TO THESE
WINDS. SHORT PERIOD NORTHWESTERLY SWELLS ARE EXPECTED BY TONIGHT.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .TDAY...SCA...PT ARENA TO PT REYES 10-60 NM UNTIL 3 PM
             GLW...PT ARENA TO PT REYES 10-60 NM FROM 3 PM
             SCA...PT REYES TO PIGEON PT 10-60 NM FROM 3 PM
             SCA...PT ARENA TO PT REYES 0-10 NM FROM NOON
             SCA...SF BAY NORTH OF THE BAY BRIDGE FROM 9 AM

&&

$$

PUBLIC FORECAST: RGASS
AVIATION/MARINE: CW

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