000
FXUS66 KMTR 171606
AFDMTR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA
906 AM PDT MON JUN 17 2013

.DISCUSSION...AS OF 9:06 AM PDT MONDAY...ONLY SOME PATCHY STRATUS
REMAINS ALONG THE COAST AND BY JUNE STANDARDS WERE OFF TO A PRETTY
SUNNY START. THE ONSHORE GRADIENT FROM SFO TO SAC IS 2.8 MB WITH
GUSTY WEST WINDS BLOWING THROUGH THE DELTA IN RESPONSE TO A DEEP
UPPER LEVEL TROUGH APPROACHING THE PACIFIC NORTHWEST COAST TODAY.
THE LARGE SCALE PATTERN WILL KEEP TEMPERATURES NEAR OR SLIGHTLY
BELOW NORMAL INLAND WITH NO REAL HOT WEATHER TO SPEAK OF. AS THE
UPPER TROUGH AXIS SWINGS ONSHORE TO OUR NORTH OVERNIGHT 850 MB
TEMPS ACROSS THE NORTH BAY WILL DROP BELOW 10 CELSIUS. THUS
COOLING ALOFT IN COMBINATION WITH GUSTY NW WINDS IN THE BOUNDARY
LAYER OVER THE OCEAN SHOULD KEEP WIDESPREAD STRATUS FORMATION MORE
PATCHY IN NATURE VERSUS A LARGE STRATIFIED CLOUD DECK OVER THE
OCEAN...SO WOULD EXPECT ONLY PATCHY BAYSIDE CLOUDS ONCE AGAIN FOR
TUESDAY MORNING. TEMPERATURES WILL REMAIN AT OR SLIGHTLY BELOW
SEASONAL NORMALS AT LEAST THROUGH WEDS. A NOTED WARMING TREND
SHOULD BEGIN BY THURSDAY AS THE TROUGH AXIS SWINGS INLAND AND HIGH
PRESSURE BUILDS WITH MORE FAVORABLE NORTHERLY/DOWNSLOPE WINDS
ACROSS THE BAY AREA. INLAND HIGHS SHOULD WARM BACK INTO THE UPPER
80S AND LOWER 90S BY FRIDAY AND SATURDAY UNDER MOSTLY CLEAR SKIES
WITH MOSTLY CLEAR AND MILD WEATHER EVEN NEAR THE COAST. BY LATE IN
THE WEEKEND OR EARLY NEXT WEEK THE RIDGE WILL BREAK DOWN WITH A
RETURN TO ONSHORE FLOW AND SEASONABLE OR SLIGHTLY BELOW NORMAL
TEMPS FOR NEXT WEEK. LONG RANGE SOLUTIONS TRYING TO BUILD A STRONG
AND WARM RIDGE OVER THE STATE AND MUCH OF THE WEST BY THE END OF
THE MONTH...WILL CONTINUE TO MONITOR MODEL TRENDS ON EVOLVING LONG
WAVE PATTERN AS JULY IS USUALLY WHEN STAGNANT UPPER PATTERN
DEVELOPS THAT WOULD FAVOR FOUR-CORNERS HIGH.

&&

.AVIATION...AS OF 4:30 AM PDT MONDAY...STRATUS WAS QUICKLY PILING
UP ALONG THE IMMEDIATE COAST THIS MORNING. FORT ORD PROFILER AS
OF 2 AM SHOWS A MARINE INVERSION JUST BEGINNING TO LIFT. MODEL
FORECASTS SHOW A WEAK UPPER TROUGH ARRIVING BY LATE MORNING AND A
SURFACE TROUGH WILL SLIDE SE ACROSS THE AREA LATE THIS AFTERNOON.
THROW IN SLOW AND STEADY LOW LEVEL COOLING PER MODEL FORECASTS AND
CONDITIONS LEAN TOWARD A STRATUS INTRUSION. TIMING IT IS EXTRA
COMPLICATED TODAY IN PART BECAUSE DIURNAL WARMING/MIXING MAY HELP
ERODE SOME OF THE STRATUS DURING THE DAYLIGHT HOURS. SO IT`S A
VERY TOUGH CALL TO SAY WHEN A SOLID LAYER OF STRATUS WILL MOVE
INLAND. WITH EXCEPTION OF WHERE THE STRATUS CLOUDS ARE ALREADY
CAUSING CIGS IT WOULD SEEM THAT THINGS ADD UP TO EITHER AN
AFTERNOON OR EVENING STRATUS INTRUSION FOR A LARGER PORTION OF THE
AREA.

VICINITY OF KSFO...PRESSURE GRADIENT DRIVEN WESTERLY WINDS HAVE
OCCURRED MUCH OF THE NIGHT. HAF-SFO GRADIENT IS PRESENTLY 2 MB. SO
FAR THE SHALLOWER MARINE LAYER DEPTH HAS HELPED PREVENT STRATUS FROM
MOVING INTO KSFO BUT IT`S NOT FAR AWAY. IT`S A LOW PROBABILITY (AND
LOW CONFIDENCE) BUT WE MIGHT JUST GET BY WITH VFR THIS MORNING. BY
EARLY AFTERNOON HOWEVER A WEAKENING OF THE EPAC SURFACE RIDGE...THE
ARRIVAL OF THE TROUGH AND A 4-5 MB SFO-SAC GRADIENT MEANS AN EARLY
STRATUS INTRUSION. BY THIS TIME CIGS HAVE A BETTER CHANCE FOR
LIFTING ABOVE 1600 FEET. 12Z TAF INDICATES TEMPO MVFR CIGS
BEGINNING 21Z. CIGS ARE LIKELY TONIGHT AS UPPER TROUGHING...ROBUST
ONSHORE WINDS AND A DEEPER AND WEAKER MARINE INVERSION PREVAIL.

KSFO BRIDGE APPROACH...SIMILAR TO KSFO. THE APPROACH HAS A CHANCE
OF STAYING VFR THIS MORNING. ARRIVAL OF LOW CLOUD COVER IS EXPECTED
BY EITHER LATE AFTERNOON OR EVENING WITH CIGS IN MVFR CATEGORY.

MONTEREY BAY AREA TERMINALS...STRATUS CONTINUES TO CONVERGE NEAR
THE PENINSULA AND FILL IN OVER THE MONTEREY BAY. IFR IS FORECAST
THIS MORNING. MVFR IS FORECAST THIS AFTERNOON. SCT-BKN IS POSSIBLE
THIS AFTERNOON DUE TO DIURNAL MIXING.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .TDAY...SCA...PT PINOS TO PT PIEDRAS BLANCAS 0-10 NM
             SCA...PIGEON PT TO PT PIEDRAS BLANCAS 10-60 NM
             SCA...SF BAY FROM 3 PM

&&

$$

PUBLIC FORECAST: RWW
AVIATION/MARINE: CANEPA

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