699
FXUS66 KMTR 181640
AFDMTR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA
940 AM PDT SUN AUG 18 2019
SYNOPSIS
COOLER TEMPERATURES WILL PREVAIL ACROSS THE REGION
TODAY, WITH SEASONABLE CONDITIONS CONTINUING THROUGH THE FIRST
PART OF THE WORK WEEK. A GRADUAL WARMING TREND WILL DEVELOP BY
WEDNESDAY AND CONTINUE THROUGH NEXT WEEKEND AS HIGHER PRESSURE
SETS UP OVER NORTHERN CALIFORNIA.
DISCUSSION...AS OF 09:40 AM PDT SUNDAY
WATER VAPOR IMAGERY
SHOWS A TROUGH OF LOW PRESSURE ALONG THE WEST COAST THIS MORNING,
WITH A WEAK DISTURBANCE MOVING INLAND ACROSS NORTHERN CALIFORNIA.
THIS DISTURBANCE HELPED DEEPEN THE MARINE LAYER OVERNIGHT TO
AROUND 3000 FEET, ACCORDING TO THE FORT ORD PROFILER. THIS
DEEPENING ALONG WITH THE UPSLOPE FLOW INTO THE COASTAL MOUNTAINS
IS ALLOWING FOR SOME DRIZZLE TO DEVELOP. ALTHOUGH THE REPORTS ARE
PRETTY HIT AND MISS, A SPOTTER FROM LIVE OAK CALLED IN TO REPORT
THAT THE DRIZZLE WAS ACCUMULATING. IN FACT, IT SEEMS LIKE THE
SANTA CRUZ MOUNTAINS AND COASTAL AREAS ARE THE BIG WINNER, WITH
OBSERVATIONS SHOWING BETWEEN 0.01 AND 0.06 INCHES. EXPECT THIS
DRIZZLE TO CONTINUE THROUGH LATE THIS MORNING, BEFORE WINDING DOWN
THIS AFTERNOON. OTHERWISE, THE MAIN FORECAST CONCERN FOR TODAY
WILL BE WITH THE COOLER CONDITIONS ACROSS THE REGION. AT THIS
TIME, THE FORECAST SHOWS THIS TREND, AND NO UPDATES ARE PLANNED AT
THIS TIME. WILL NEED TO WATCH THE INLAND AREAS THOUGH, AS THEY
MAY NOT GET QUITE AS WARM AS THE CURRENT FORECAST REFLECTS.
THIS UPPER LEVEL TROUGH WILL REMAIN ALONG THE WEST COAST THROUGH
THE FIRST PART OF THE WORK WEEK, WITH A SECONDARY WEAK DISTURBANCE
FORECAST TO MOVE INLAND DURING THE DAY ON MONDAY. THEREFORE,
EXPECT THE MARINE LAYER TO REMAIN ON THE DEEP SIDE TONIGHT, WITH
ANOTHER GOOD INLAND PUSH TONIGHT. TEMPERATURES BEING SIMILAR TO
TODAY OR SLIGHTLY COOLER DEPENDING ON LOCATION, BUT BE WITHIN
SEASONAL NORMS. A GRADUAL WARMING TREND WILL THEN DEVELOP FOR
MIDWEEK AND NEXT WEEKEND, AS HIGH PRESSURE SLOWLY BUILDS BACK INTO
THE REGION. PALMER
PREVIOUS DISCUSSION
/ISSUED AT 03:03 AM PDT SUNDAY/
THE LONG WAVE TROUGH OVER THE BAY AREA DEEPENS TONIGHT AND INTO
TOMORROW. THE FORT ORD PROFILER ALREADY HAS A MARINE LAYER
APPROXIMATED AT OVER 3000 FEET AS LOW CLOUDS ARE SEEN ON SATELLITE
OVER THE SANTA CRUZ MOUNTAINS AND MONTEREY BAY, DOWN THE SALINAS
VALLEY AND MAKING ITS WAY FURTHER INLAND. SMALL CHANCES OF PATCHY
DRIZZLE ARE EXPECTED FOR THE COASTS OF SAN MATEO AND SANTA CRUZ
COUNTIES AS WELL AS ISOLATED AREAS ALONG THE BIG SUR COAST THROUGH
MID-MORNING AS LOW LEVEL ONSHORE FLOW PERSISTS. CLOUDS SHOULD
CLEAR FOR MOST INLAND AREAS BY THE AFTERNOON ON SUNDAY, BUT SOME
COASTAL AREAS WILL MOST LIKELY SEE CLOUDS REMAIN ALL DAY. THE
DEEPENING TROUGH SUNDAY, WITH THE AIDE OF A DEEPER MARINE LAYER
AND PERSISTENT ONSHORE FLOW, WILL SEE COOLER TEMPERATURES ONCE
AGAIN AROUND THE BAY AREA. THOUGH IT WILL BE A SMALLER COOLING
COMPARED TO WHAT WAS EXPERIENCED SATURDAY, INTERIOR LOCATIONS ARE
EXPECTED TO SEE THE MOST COOL DOWN DUE TO THE INLAND EXTENT OF THE
ONSHORE FLOW.
BY MONDAY AND INTO TUESDAY, HIGH PRESSURE BEGINS TO REBUILD OVER
CENTRAL TEXAS. TEMPERATURES AROUND THE BAY AREA WILL SLOWLY INCREASE
AS THE UPPER RIDGE OVER THE SOUTHERN PLAINS SHIFTS WESTWARD, RAISING
HEIGHTS OVER CALIFORNIA. MORE ROBUST WARMING IS FORECAST BY MID-TO-
END OF WEEK. THIS WARM-UP WILL NOT BE OF THE SAME MAGNITUDE AS THIS
PREVIOUS WEEK'S HEAR, DUE TO AN APPROACHING TROUGH FROM THE WEST.
LONGER RANGE MODELS SHOW THAT BY NEXT WEEKEND, A RIDGE BUILDS OFF
THE COAST OF NORTHERN CALIFORNIA. THIS WILL BE THE NEXT OPPORTUNITY
TO BRING POTENTIALLY SIGNIFICANT HEATING TO THE BAY AREA BUT ALSO
THE CHANGE OF ONSHORE FLOW TO OFFSHORE.
AVIATION...AS OF 5:05 AM PDT SUNDAY
NEARLY CONTINUOUS LOW
CLOUDS /MVFR/ EXTENDS NORTHWARD FROM THE CENTRAL COAST TO THE
SANTA CRUZ MOUNTAINS AND NORTHWARD TO COASTAL SONOMA COUNTY AND IS
ADVANCING INTO THE SOUTH BAY; 2.9 MB SMX-SFO AND 2.4 MB SNS-SJC
PRESSURE GRADIENTS ARE FORECAST TO WANE TODAY ALLOWING AN
AFTERNOON AND EVENING 3 MB SFO-SAC ONSHORE GRADIENT AND WIND TO
PREVAIL LATER TODAY AND AGAIN LATER MONDAY. LOW CLOUDS /MVFR/
CONTINUE TO FILL IN OVER THE NORTH BAY VALLEYS. PATCHY MVFR
CEILINGS ARE OTHERWISE FOUND OVER THE BAY AREA WHILE WELL INLAND
IT'S VFR. THE WEATHER TODAY INTO MONDAY IS DRIVEN BY COOLING AND A
DEEPENING MARINE LAYER, PATCHY MORNING COASTAL DRIZZLE IS ALSO
POSSIBLE. GUSTY SW WINDS STILL REPORTED AT PACHECO PASS NORTHWARD
TO A FEW LOCATIONS IN THE EAST BAY, OTHERWISE LIGHTER WINDS ALL
LOCATIONS. WHERE GUSTY WINDS LINGER THEY SHOULD DIMINISH THIS
MORNING AS THE SOUTH TO NORTH SURFACE PRESSURE PATTERN OVER NORCAL
BECOMES MUCH MORE BALANCED AND FLAT, ONSHORE WINDS BECOMING THE
PRIMARY FOCUS TODAY THROUGH MONDAY.
VICINITY OF KSFO...VFR, SOUTH WIND 5 TO 10 KNOTS SHIFTING OVER SW
THEN W BY LATE MORNING OR EARLY AFTERNOON AND INCREASING TO NEAR
15 KNOTS. LIGHTER WIND TONIGHT AND MONDAY MORNING.
SFO BRIDGE APPROACH...SIMILAR TO KSFO.
MONTEREY BAY TERMINALS...MVFR CEILINGS WITH LIGHT WINDS AND PATCHY
DRIZZLE IN THE MORNING, VFR BY LATE MORNING OR EARLY AFTERNOON AND
ONSHORE WINDS 10 TO 15 KNOTS. LOW CLOUDS /MVFR/ RETURNS THIS EVENING
WITH MVFR TONIGHT INTO MONDAY MORNING.
MARINE...AS OF 8:47 AM PDT SUNDAY
WINDS WILL DIMINISH THROUGH
MID WEEK AS HIGH PRESSURE WEAKENS OFF THE CALIFORNIA COAST AND A
LOW PRESSURE SYSTEM DEVELOPS OFF OF BRITISH COLUMBIA. SHORTER
PERIOD NORTHWEST WAVES AT AROUND 8 TO 10 SECONDS WILL CONTINUE TO
BE THE DOMINATE FEATURE THROUGH MUCH OF THE WEEK ALONG WITH A
LIGHT SOUTHERLY SWELL.
MTR WATCHES/WARNINGS/ADVISORIES
.TDAY...SCA...PT ARENA TO PIGEON PT 10-60 NM UNTIL 9 AM
PUBLIC FORECAST: PALMER / DK
AVIATION: CANEPA
MARINE: AS
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