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FXUS66 KMTR [Monterey CA] 051721 AFDMTR 

FXUS66 KMTR 051721
AFDMTR [HEAD]

National Weather Service San Francisco Bay Area
Issued by National Weather Service Los Angeles/Oxnard California 9:21am PST Sat Dec 5 2020 

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA
ISSUED BY NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
921 AM PST SAT DEC 5 2020 [HEAD]

Synopsis. Slight cooling trend through the weekend while a weak cold front moves into Northern California. The upper low associated with that cold front will slide southward Sunday night and retrograde back towards the coast through Monday. This pattern will create offshore flow with gusty winds over the mountains during that period. Afterwards, dry weather with mild daytime highs and cool nights will persist for the rest of the week. 

.SYNOPSIS...SLIGHT COOLING TREND THROUGH THE WEEKEND WHILE A WEAK
COLD FRONT MOVES INTO NORTHERN CALIFORNIA. THE UPPER LOW
ASSOCIATED WITH THAT COLD FRONT WILL SLIDE SOUTHWARD SUNDAY NIGHT
AND RETROGRADE BACK TOWARDS THE COAST THROUGH MONDAY. THIS PATTERN
WILL CREATE OFFSHORE FLOW WITH GUSTY WINDS OVER THE MOUNTAINS
DURING THAT PERIOD. AFTERWARDS, DRY WEATHER WITH MILD DAYTIME
HIGHS AND COOL NIGHTS WILL PERSIST FOR THE REST OF THE WEEK. [DISC]

Discussion. As of 08:37am PST Saturday… water vapor imagery this morning captures the elongated moisture plume just off the coast advecting moisture primarily into British Columbia this morning, while the Pacific Northwest is expected to receive modest returns over the next few hours. As for our CWA [County Warning Area; see the LWP home page (link at bottom of page) for a CWA map], the rail-end of the plume will introduce a weak frontal passage over northern and central California this afternoon. As such, expecting cloud cover to increase starting around late-morning in the North Bay before trickling into the Central Coast. Moderate air quality conditions are being observed in places like the Santa Clara Valley but should see some relief this afternoon as weak onshore flow clears out some of the haze. 

.DISCUSSION...AS OF 08:37 AM PST SATURDAY...WATER VAPOR IMAGERY
THIS MORNING CAPTURES THE ELONGATED MOISTURE PLUME JUST OFF THE
COAST ADVECTING MOISTURE PRIMARILY INTO BRITISH COLUMBIA THIS
MORNING, WHILE THE PAC NW IS EXPECTED TO RECEIVE MODEST RETURNS
OVER THE NEXT FEW HOURS. AS FOR OUR CWA, THE RAIL-END OF THE PLUME
WILL INTRODUCE A WEAK FROPA OVER NORTHERN AND CENTRAL CALIFORNIA
THIS AFTERNOON. AS SUCH, EXPECTING CLOUD COVER TO INCREASE
STARTING AROUND LATE-MORNING IN THE NORTH BAY BEFORE TRICKLING
INTO THE CENTRAL COAST. MODERATE AIR QUALITY CONDITIONS ARE BEING
OBSERVED IN PLACES LIKE THE SANTA CLARA VALLEY BUT SHOULD SEE SOME
RELIEF THIS AFTERNOON AS WEAK ONSHORE FLOW CLEARS OUT SOME OF THE
HAZE. [DISC]

For the latest on air quality conditions please refer to airnow and/or the Bay Area air quality district. 

FOR THE LATEST ON AIR QUALITY CONDITIONS PLEASE REFER TO AIRNOW
AND/OR THE BAY AREA AIR QUALITY DISTRICT. [DISC]

Previous discussion… as of 03:12am PST Saturday. No significant changes to the forecast as we await the weak cold front to move inland later today. Models don't show much precipitation with this system, but from this evening into early Sunday there is a slight chance for brief, light showers… mainly in the North Bay, but wouldn't be surprised if there was light drizzle elsewhere. As this system passes through, RH [Relative Humidity] recoveries will increase across the region which is good timing to mitigate fire weather concerns with the drying offshore winds we expect Sunday night into Monday. Timing seems to be on our side with a dose of moisture first, then the gusty offshore winds, but by the time the drier flow starts to lower RH [Relative Humidity] values into the teens on Monday afternoon, the wind speeds will decrease. That's not to say there won't be any fire weather concerns, but at least the timing of gusty winds and driest conditions won't coincide to exacerbate any fire starts. 

.PREV DISCUSSION...AS OF 03:12 AM PST SATURDAY... NO SIGNIFICANT
CHANGES TO THE FORECAST AS WE AWAIT THE WEAK COLD FRONT TO MOVE
INLAND LATER TODAY. MODELS DON`T SHOW MUCH PRECIPITATION WITH THIS
SYSTEM, BUT FROM THIS EVENING INTO EARLY SUNDAY THERE IS A SLIGHT
CHANCE FOR BRIEF, LIGHT SHOWERS...MAINLY IN THE NORTH BAY, BUT
WOULDN`T BE SURPRISED IF THERE WAS LIGHT DRIZZLE ELSEWHERE. AS
THIS SYSTEM PASSES THROUGH, RH RECOVERIES WILL INCREASE ACROSS THE
REGION WHICH IS GOOD TIMING TO MITIGATE FIRE WEATHER CONCERNS
WITH THE DRYING OFFSHORE WINDS WE EXPECT SUNDAY NIGHT INTO MONDAY.
TIMING SEEMS TO BE ON OUR SIDE WITH A DOSE OF MOISTURE FIRST,
THEN THE GUSTY OFFSHORE WINDS, BUT BY THE TIME THE DRIER FLOW
STARTS TO LOWER RH VALUES INTO THE TEENS ON MONDAY AFTERNOON, THE
WIND SPEEDS WILL DECREASE. THAT`S NOT TO SAY THERE WON`T BE ANY
FIRE WEATHER CONCERNS, BUT AT LEAST THE TIMING OF GUSTY WINDS AND
DRIEST CONDITIONS WON`T COINCIDE TO EXACERBATE ANY FIRE STARTS. [DISC]

An upper level ridge will build into Northern California Monday into Tuesday. That coupled with the warmer offshore winds will bring a warming trend to our daytime highs. Residents across our CWA [County Warning Area; see the LWP home page (link at bottom of page) for a CWA map] can expect Monday and Tuesday to be our warmest days with highs ranging upper 60s to upper 70s and some of our climate sites may flirt with Max temp records on those days. By Wednesday an upper level trough over the Pacific Northwest will dig southward into Northern California and bring a cooler airmass as we go experience a cooling trend for the rest of the week. Overnight lows could get chilly by the end of next week, but should generally stay above freezing… around mid 30s in the inland valleys and mid 40s along the coast/SF Bay Area. 

AN UPPER LEVEL RIDGE WILL BUILD INTO NORCAL MONDAY INTO TUESDAY.
THAT COUPLED WITH THE WARMER OFFSHORE WINDS WILL BRING A WARMING
TREND TO OUR DAYTIME HIGHS. RESIDENTS ACROSS OUR CWA CAN EXPECT
MONDAY AND TUESDAY TO BE OUR WARMEST DAYS WITH HIGHS RANGING UPPER
60S TO UPPER 70S AND SOME OF OUR CLIMATE SITES MAY FLIRT WITH MAX
TEMP RECORDS ON THOSE DAYS. BY WEDNESDAY AN UPPER LEVEL TROUGH
OVER THE PACIFIC NW WILL DIG SOUTHWARD INTO NORCAL AND BRING A
COOLER AIRMASS AS WE GO EXPERIENCE A COOLING TREND FOR THE REST OF
THE WEEK. OVERNIGHT LOWS COULD GET CHILLY BY THE END OF NEXT
WEEK, BUT SHOULD GENERALLY STAY ABOVE FREEZING...AROUND MID 30S IN
THE INLAND VALLEYS AND MID 40S ALONG THE COAST/SF BAY AREA. [DISC]

Aviation. As of 03:32am PST Saturday… for the 12Z [4am PST] TAFs [Terminal Aerodrome Forecasts]. VFR [Visual Flight Rules] conditions to prevail with increasing high clouds throughout the period as a weak front approaches. Precipitation with this system is highly unlikely, but some light drizzle will be possible. Ceilings will gradually lower this evening and overnight from north to south with MVFR [Marginal Visual Flight Rules] (locally IFR [Instrument Flight Rules]) conditions towards the end of the TAF [Terminal Aerodrome Forecast] period. Generally light winds through the period. 

.AVIATION...AS OF 03:32 AM PST SATURDAY...FOR THE 12Z TAFS. VFR
CONDITIONS TO PREVAIL WITH INCREASING HIGH CLOUDS THROUGHOUT THE
PERIOD AS A WEAK FRONT APPROACHES. PRECIPITATION WITH THIS SYSTEM
IS HIGHLY UNLIKELY, BUT SOME LIGHT DRIZZLE WILL BE POSSIBLE. CIGS
WILL GRADUALLY LOWER THIS EVENING AND OVERNIGHT FROM NORTH TO
SOUTH WITH MVFR (LOCALLY IFR) CONDITIONS TOWARDS THE END OF THE
TAF PERIOD. GENERALLY LIGHT WINDS THROUGH THE PERIOD. [AVIA]

Vicinity of KSFO [San Francisco CA]VFR [Visual Flight Rules] with increasing high clouds throughout the day. Ceilings expected to gradually lower overnight with MVFR [Marginal Visual Flight Rules] conditions possible tonight and tomorrow morning. Light winds this morning turning onshore late this afternoon around 10 kt [12 mph] or less. 

VICINITY OF KSFO...VFR WITH INCREASING HIGH CLOUDS THROUGHOUT THE
DAY. CIGS EXPECTED TO GRADUALLY LOWER OVERNIGHT WITH MVFR
CONDITIONS POSSIBLE TONIGHT AND TOMORROW MORNING. LIGHT WINDS THIS
MORNING TURNING ONSHORE LATE THIS AFTERNOON AROUND 10 KT OR LESS. [AVI2]

SFO [San Francisco CA] bridge approach… similar to KSFO [San Francisco CA]

SFO BRIDGE APPROACH...SIMILAR TO KSFO. [AVI2]

Monterey Bay terminals… VFR [Visual Flight Rules] with increasing high clouds throughout the day. Possibility of increasing low level moisture late this afternoon and MVFR [Marginal Visual Flight Rules]/IFR [Instrument Flight Rules] ceilings over the peninsula into this evening, but confidence is low. Lowering ceilings towards the end of the TAF [Terminal Aerodrome Forecast] period ahead of a weak cold front. Locally breezy SE winds this morning down the Salinas Valley 10–15 kt [12–17 mph], should ease mid to late morning. Onshore winds this afternoon around 10 kt [12 mph]

MONTEREY BAY TERMINALS...VFR WITH INCREASING HIGH CLOUDS
THROUGHOUT THE DAY. POSSIBILITY OF INCREASING LOW LEVEL MOISTURE
LATE THIS AFTERNOON AND MVFR/IFR CIGS OVER THE PENINSULA INTO THIS
EVENING, BUT CONFIDENCE IS LOW. LOWERING CIGS TOWARDS THE END OF
THE TAF PERIOD AHEAD OF A WEAK COLD FRONT. LOCALLY BREEZY SE WINDS
THIS MORNING DOWN THE SALINAS VALLEY 10-15 KT, SHOULD EASE MID TO
LATE MORNING. ONSHORE WINDS THIS AFTERNOON AROUND 10 KT. [AVI2]

Marine. As of 09:08am PST Saturday… light to locally moderate north to northwest winds will continue through early this morning as long period NW swell slowly subsides. Winds will turn southerly across much of the waters today as a weak front approaches. Northerly winds will return tonight into Sunday morning and gradually increase throughout the day. West to northwest swell will also build late this weekend. The combination of breezy winds and building seas will result in hazardous seas conditions, particularly for smaller vessels. Another longer period large amplitude swell will arrive Monday night into Tuesday. 

.MARINE...AS OF 09:08 AM PST SATURDAY...LIGHT TO LOCALLY MODERATE
NORTH TO NORTHWEST WINDS WILL CONTINUE THROUGH EARLY THIS MORNING
AS LONG PERIOD NW SWELL SLOWLY SUBSIDES. WINDS WILL TURN
SOUTHERLY ACROSS MUCH OF THE WATERS TODAY AS A WEAK FRONT
APPROACHES. NORTHERLY WINDS WILL RETURN TONIGHT INTO SUNDAY
MORNING AND GRADUALLY INCREASE THROUGHOUT THE DAY. WEST TO
NORTHWEST SWELL WILL ALSO BUILD LATE THIS WEEKEND. THE COMBINATION
OF BREEZY WINDS AND BUILDING SEAS WILL RESULT IN HAZARDOUS SEAS
CONDITIONS, PARTICULARLY FOR SMALLER VESSELS. ANOTHER LONGER
PERIOD LARGE AMPLITUDE SWELL WILL ARRIVE MONDAY NIGHT INTO
TUESDAY. [AVIA]

MTR Watches/Warnings/Advisories

  • Today: none. 
.MTR WATCHES/WARNINGS/ADVISORIES...
.TDAY...NONE. [WARN]

Public Forecast: GD/Bingaman; Aviation: AS; Marine: AS 

PUBLIC FORECAST: GD/BINGAMAN
AVIATION: AS
MARINE: AS [CRED]
VISIT US AT WWW.WEATHER.GOV/SANFRANCISCO [LINK]

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Point Forecast

Half Moon Bay CA

05 Dec 01:15pm PST

This Afternoon Mostly cloudy, with a high near 61°. WSW wind 5 to 7 mph.
Tonight Increasing clouds, with a low around 44°. SW wind 5 to 7 mph becoming calm in the evening.
Sunday Cloudy through mid morning, then gradual clearing, with a high near 60°. North wind 3 to 7 mph.
Sunday Night Partly cloudy, with a low around 46°. NNE wind 7 to 16 mph, with gusts as high as 23 mph.
Monday Sunny, with a high near 66°. NE wind 13 to 18 mph, with gusts as high as 26 mph.
Monday Night Mostly clear, with a low around 48°.
Tuesday Sunny, with a high near 66°.
Tuesday Night Partly cloudy, with a low around 44°.
Wednesday Mostly sunny, with a high near 63°.
Wednesday Night Partly cloudy, with a low around 45°.
Thursday Mostly sunny, with a high near 61°.
Thursday Night Partly cloudy, with a low around 43°.
Friday Mostly sunny, with a high near 59°.
This Afternoon
Mostly cloudy, with a high near 61. West southwest wind 5 to 7 mph.
Tonight
Increasing clouds, with a low around 44. Southwest wind 5 to 7 mph becoming calm in the evening.
Sunday
Cloudy through mid morning, then gradual clearing, with a high near 60. North wind 3 to 7 mph.
Sunday Night
Partly cloudy, with a low around 46. North northeast wind 7 to 16 mph, with gusts as high as 23 mph.
Monday
Sunny, with a high near 66. Northeast wind 13 to 18 mph, with gusts as high as 26 mph.
Monday Night
Mostly clear, with a low around 48.
Tuesday
Sunny, with a high near 66.
Tuesday Night
Partly cloudy, with a low around 44.
Wednesday
Mostly sunny, with a high near 63.
Wednesday Night
Partly cloudy, with a low around 45.
Thursday
Mostly sunny, with a high near 61.
Thursday Night
Partly cloudy, with a low around 43.
Friday
Mostly sunny, with a high near 59.

This page is generated dynamically from the National Weather Service's NWS point forecast and Area Forecast Discussion, reformatted for readability. NWS glossary; about point forecasts. For more information, visit the Lobitos Weather Project home page. Comments and corrections are welcome: