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FXUS66 KMTR [Monterey CA] 041212 AFDMTR 

FXUS66 KMTR 041212
AFDMTR [HEAD]

National Weather Service San Francisco Bay Area 5:12am PDT Sat Apr 4 2020 

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA
512 AM PDT SAT APR 4 2020 [HEAD]

Synopsis. Forecast remains on track with North Bay rain this morning spreading over the Bay Area this afternoon and reaching the Central Coast by late afternoon/evening. Rainfall today will mostly be light, though moderate at times in the North Bay. Showers overnight become a steady rain on Sunday as another system drops down the coast. Locally heavy rain, possible thunderstorms and gusty winds during the day Sunday. Precipitation becomes showers Sunday night into Monday as the upper low passes over the region. Showers may linger for the Central Coast Tuesday and Wednesday as the upper low slowly exits the region followed by a warming and drying trend for the second half of next week. 

.SYNOPSIS...FORECAST REMAINS ON TRACK WITH NORTH BAY RAIN THIS
MORNING SPREADING OVER THE BAY AREA THIS AFTERNOON AND REACHING
THE CENTRAL COAST BY LATE AFTERNOON/EVENING. RAINFALL TODAY WILL
MOSTLY BE LIGHT, THOUGH MODERATE AT TIMES IN THE NORTH BAY.
SHOWERS OVERNIGHT BECOME A STEADY RAIN ON SUNDAY AS ANOTHER SYSTEM
DROPS DOWN THE COAST. LOCALLY HEAVY RAIN, POSSIBLE THUNDERSTORMS
AND GUSTY WINDS DURING THE DAY SUNDAY. PRECIPITATION BECOMES
SHOWERS SUNDAY NIGHT INTO MONDAY AS THE UPPER LOW PASSES OVER THE
REGION. SHOWERS MAY LINGER FOR THE CENTRAL COAST TUESDAY AND
WEDNESDAY AS THE UPPER LOW SLOWLY EXITS THE REGION FOLLOWED BY A
WARMING AND DRYING TREND FOR THE SECOND HALF OF NEXT WEEK. [DISC]

Discussion. As of 3:41am PDT Saturday… forecast remains on track early this morning with no big changes in timing or intensity of incoming storms. Rain has reached the north coast with Arcata reporting light rain. We are just starting to get some returns on radar off the Mendocino/Sonoma coast. Short term models bring rain onshore between 14–16Z [7–9am PDT] then spreading southward over the Bay Area through the day before reaching the Central Coast late afternoon/evening hours. This initial storm won't pack too much punch and mainly expecting light rainfall today as the main energy passes to our north. Scattered showers overnight will become a steady rain by Sunday morning as a deeper trough drops down the coast. There will be better jet dynamics with diffluence aloft, steeper lapse rates [The rate of change of an atmospheric variable, usually temperature, with height. A steep lapse rate implies a rapid decrease in temperature with height (a sign of instability) and a steepening lapse rate implies that destabilization is occurring.] and a more well defined surface boundary with stronger surface forcing and upslope flow to produce some locally heavy rain. The boundary looks fairly progressive on Sunday and last few model runs have focused heaviest rains from the Santa Cruz Mountains southward to the Santa Lucia Range above Big Sur. This is not an atmospheric river but rather a cold core system so rain totals of around 0.75–1.50 inches for the valleys with 2–3 inches for the hills when all is said and done. Most of the climate sites around the Bay Area are running 40–50% of normal so this will be one last chance to put some dents into the season rainfall deficits. Last few model runs have kept the core of the upper low and thus the associated cold air farther offshore. This has reduced thunderstorm chances on the model solutions though some isolated thunderstorms-storms later Sunday afternoon through Monday afternoon will still be possible. 

.DISCUSSION...AS OF 3:41 AM PDT SATURDAY...FORECAST REMAINS ON
TRACK EARLY THIS MORNING WITH NO BIG CHANGES IN TIMING OR
INTENSITY OF INCOMING STORMS. RAIN HAS REACHED THE NORTH COAST
WITH ARCATA REPORTING LIGHT RAIN. WE ARE JUST STARTING TO GET SOME
RETURNS ON RADAR OFF THE MENDOCINO/SONOMA COAST. SHORT TERM
MODELS BRING RAIN ONSHORE BETWEEN 14-16Z THEN SPREADING SOUTHWARD
OVER THE BAY AREA THROUGH THE DAY BEFORE REACHING THE CENTRAL
COAST LATE AFTERNOON/EVENING HOURS. THIS INITIAL STORM WONT PACK
TOO MUCH PUNCH AND MAINLY EXPECTING LIGHT RAINFALL TODAY AS THE
MAIN ENERGY PASSES TO OUR NORTH. SCATTERED SHOWERS OVERNIGHT WILL
BECOME A STEADY RAIN BY SUNDAY MORNING AS A DEEPER TROUGH DROPS
DOWN THE COAST. THERE WILL BE BETTER JET DYNAMICS WITH DIFFLUENCE
ALOFT, STEEPER LAPSE RATES AND A MORE WELL DEFINED SURFACE
BOUNDARY WITH STRONGER SURFACE FORCING AND UPSLOPE FLOW TO PRODUCE
SOME LOCALLY HEAVY RAIN. THE BOUNDARY LOOKS FAIRLY PROGRESSIVE ON
SUNDAY AND LAST FEW MODEL RUNS HAVE FOCUSED HEAVIEST RAINS FROM
THE SANTA CRUZ MTNS SOUTHWARD TO THE SANTA LUCIA RANGE ABOVE BIG
SUR. THIS IS NOT AN ATMOSPHERIC RIVER BUT RATHER A COLD CORE
SYSTEM SO RAIN TOTALS OF AROUND 0.75-1.50 INCHES FOR THE VALLEYS
WITH 2-3 INCHES FOR THE HILLS WHEN ALL IS SAID AND DONE. MOST OF
THE CLIMATE SITES AROUND THE BAY AREA ARE RUNNING 40-50% OF NORMAL
SO THIS WILL BE ONE LAST CHANCE TO PUT SOME DENTS INTO THE SEASON
RAINFALL DEFICITS. LAST FEW MODEL RUNS HAVE KEPT THE CORE OF THE
UPPER LOW AND THUS THE ASSOCIATED COLD AIR FARTHER OFFSHORE. THIS
HAS REDUCED T-STORM CHANCES ON THE MODEL SOLUTIONS THOUGH SOME
ISOLATED T-STORMS LATER SUNDAY AFTERNOON THROUGH MONDAY AFTERNOON
WILL STILL BE POSSIBLE. [DISC]

Precipitation will turn showery on Sunday night as the main surface boundary moves through. Shower chances stay in the forecast Monday but if the 06Z [11pm PDT] NAM [North American Meso (formerly Eta) model] is right the best forcing stays offshore and activity looks to be scattered at best with the higher terrain of the Central Coast the most likely location for some thunderstorms on Monday. Snow levels aren't as low as previously forecast due to the upper low staying offshore. On Sunday when the steady precipitation fall the snow levels stay well above 4000 feet, then lowering to around 3500 feet by Monday when precipitation becomes more showery. 

PRECIP WILL TURN SHOWERY ON SUNDAY NIGHT AS THE MAIN SURFACE
BOUNDARY MOVES THROUGH. SHOWER CHANCES STAY IN THE FORECAST MONDAY
BUT IF THE 06Z NAM IS RIGHT THE BEST FORCING STAYS OFFSHORE AND
ACTIVITY LOOKS TO BE SCATTERED AT BEST WITH THE HIGHER TERRAIN OF
THE CENTRAL COAST THE MOST LIKELY LOCATION FOR SOME T-STORMS ON
MONDAY. SNOW LEVELS AREN`T AS LOW AS PREVIOUSLY FORECAST DUE TO
THE UPPER LOW STAYING OFFSHORE. ON SUNDAY WHEN THE STEADY PRECIP
FALL THE SNOW LEVELS STAY WELL ABOVE 4000 FEET, THEN LOWERING TO
AROUND 3500 FEET BY MONDAY WHEN PRECIP BECOMES MORE SHOWERY. [DISC]

Shower chances linger for the Central Coast on Tuesday with the upper low over Southern California. The operational ECMWF [European Center for Medium-Range Weather Forecasts model] would keep shower threat going into Wednesday with slow moving low but blend of models suggest we should see drying by Wednesday with a ridge building by Thursday and Friday. 

SHOWER CHANCES LINGER FOR THE CENTRAL COAST ON TUESDAY WITH THE
UPPER LOW OVER SOUTHERN CALIFORNIA. THE OPERATIONAL ECMWF WOULD
KEEP SHOWER THREAT GOING INTO WEDS WITH SLOW MOVING LOW BUT BLEND
OF MODELS SUGGEST WE SHOULD SEE DRYING BY WEDS WITH A RIDGE
BUILDING BY THURSDAY AND FRIDAY. [DISC]

Aviation. As of 5:12am PDT Saturday… for 12Z [5am PDT] TAFs [Terminal Aerodrome Forecasts]. VFR [Visual Flight Rules] to MVFR [Marginal Visual Flight Rules] ceilings and visibilities with light rain developing today. Showery weather develops tonight and Sunday with a cold upper level low arriving from the Gulf of Alaska. Strong and gusty winds developing Sunday morning per recent statistical guidance. 

.AVIATION...AS OF 5:12 AM PDT SATURDAY...FOR 12Z TAFS. VFR TO
MVFR CEILINGS AND VISIBILITIES WITH LIGHT RAIN DEVELOPING TODAY.
SHOWERY WEATHER DEVELOPS TONIGHT AND SUNDAY WITH A COLD UPPER
LEVEL LOW ARRIVING FROM THE GULF OF ALASKA. STRONG AND GUSTY WINDS
DEVELOPING SUNDAY MORNING PER RECENT STATISTICAL GUIDANCE. [AVIA]

Vicinity of KSFO [San Francisco CA]VFR [Visual Flight Rules], temporary light rain 15Z [8am PDT]-18Z [11am PDT] with ceilings gradually lowering to MVFR [Marginal Visual Flight Rules] today. Wind from the southwest today. South to southeast tonight and Sunday and strengthening per recent statistical guidance, could get close to Airport Weather Warning criteria near 35 knots [40 mph]

VICINITY OF KSFO...VFR, TEMPO LIGHT RAIN 15Z-18Z WITH CEILINGS
GRADUALLY LOWERING TO MVFR TODAY. WIND FROM THE SOUTHWEST TODAY.
SOUTH TO SOUTHEAST TONIGHT AND SUNDAY AND STRENGTHENING PER RECENT
STATISTICAL GUIDANCE, COULD GET CLOSE TO AIRPORT WEATHER WARNING
CRITERIA NEAR 35 KNOTS. [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] to MVFR [Marginal Visual Flight Rules] ceilings, light rain developing late morning to afternoon. MVFR [Marginal Visual Flight Rules] ceilings later today, tonight and Sunday morning. 

MONTEREY BAY TERMINALS...VFR TO MVFR CEILINGS, LIGHT RAIN DEVELOPING
LATE MORNING TO AFTERNOON. MVFR CEILINGS LATER TODAY, TONIGHT AND
SUNDAY MORNING. [AVI2]

Marine. As of 5:01am PDT Saturday… winds will shift to southwesterly as a warm front moves eastward over the coastal waters and bays today. The warm front will move to the north Central Coast tonight and become replaced by a cold upper level low and cold front from the Gulf of Alaska on Sunday. Wet weather will develop today and continue into early next week. High pressure will bring a return of drier weather by the middle of next week. A prevailing moderate northwesterly swell will last through much of the forecast period. 

.MARINE...AS OF 5:01 AM PDT SATURDAY...WINDS WILL SHIFT TO
SOUTHWESTERLY AS A WARM FRONT MOVES EASTWARD OVER THE COASTAL
WATERS AND BAYS TODAY. THE WARM FRONT WILL MOVE TO THE NORTH
CENTRAL COAST TONIGHT AND BECOME REPLACED BY A COLD UPPER LEVEL
LOW AND COLD FRONT FROM THE GULF OF ALASKA ON SUNDAY. WET WEATHER
WILL DEVELOP TODAY AND CONTINUE INTO EARLY NEXT WEEK. HIGH
PRESSURE WILL BRING A RETURN OF DRIER WEATHER BY THE MIDDLE OF
NEXT WEEK. A PREVAILING MODERATE NORTHWESTERLY SWELL WILL LAST
THROUGH MUCH OF THE FORECAST PERIOD. [AVIA]

MTR Watches/Warnings/Advisories

  • Today: Small Craft AdvisoryPt Pinos [Monterey CA] to Pt Piedras Blancas [San Simeon CA] 0–10 nm [11 miles] until 9am 
.MTR WATCHES/WARNINGS/ADVISORIES...
.TDAY...SCA...PT PINOS TO PT PIEDRAS BLANCAS 0-10 NM UNTIL 9 AM [WARN]

Public Forecast: RWW; Aviation/Marine: Canepa 

PUBLIC FORECAST: RWW
AVIATION/MARINE: CANEPA [CRED]
VISIT US AT WWW.WEATHER.GOV/SANFRANCISCO [LINK]

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Point Forecast

Half Moon Bay CA

04 Apr 06:55am PDT

Today Rain, mainly after 11am. High near 58°. SW wind 9 to 16 mph, with gusts as high as 22 mph. Chance of precipitation is 80%. New precipitation amounts between a half and three quarters of an inch possible.
Tonight Rain likely. Mostly cloudy, with a low around 46°. SSW wind 11 to 15 mph, with gusts as high as 20 mph. Chance of precipitation is 70%. New precipitation amounts between a tenth and quarter of an inch possible.
Sunday Rain. High near 56°. Breezy, with a SSW wind 19 to 24 mph decreasing to 13 to 18 mph in the afternoon. Winds could gust as high as 33 mph. Chance of precipitation is 100%. New precipitation amounts between a quarter and half of an inch possible.
Sunday Night A 50% chance of rain. Mostly cloudy, with a low around 42°. WSW wind 8 to 13 mph becoming light and variable after midnight. New precipitation amounts of less than a tenth of an inch possible.
Monday Rain likely, mainly after 11am. Partly sunny, with a high near 56°. Calm wind becoming west 5 to 7 mph in the afternoon. Chance of precipitation is 60%. New precipitation amounts of less than a tenth of an inch possible.
Monday Night A 20% chance of rain before 11pm. Mostly cloudy, with a low around 42°.
Tuesday Mostly sunny, with a high near 59°.
Tuesday Night Partly cloudy, with a low around 44°.
Wednesday Mostly sunny, with a high near 62°.
Wednesday Night Mostly clear, with a low around 46°.
Thursday Sunny, with a high near 65°.
Thursday Night Mostly clear, with a low around 47°.
Friday Sunny, with a high near 64°.
Today
Rain, mainly after 11am. High near 58. Southwest wind 9 to 16 mph, with gusts as high as 22 mph. Chance of precipitation is 80%. New precipitation amounts between a half and three quarters of an inch possible.
Tonight
Rain likely. Mostly cloudy, with a low around 46. South southwest wind 11 to 15 mph, with gusts as high as 20 mph. Chance of precipitation is 70%. New precipitation amounts between a tenth and quarter of an inch possible.
Sunday
Rain. High near 56. Breezy, with a south southwest wind 19 to 24 mph decreasing to 13 to 18 mph in the afternoon. Winds could gust as high as 33 mph. Chance of precipitation is 100%. New precipitation amounts between a quarter and half of an inch possible.
Sunday Night
A 50 percent chance of rain. Mostly cloudy, with a low around 42. West southwest wind 8 to 13 mph becoming light and variable after midnight. New precipitation amounts of less than a tenth of an inch possible.
Monday
Rain likely, mainly after 11am. Partly sunny, with a high near 56. Calm wind becoming west 5 to 7 mph in the afternoon. Chance of precipitation is 60%. New precipitation amounts of less than a tenth of an inch possible.
Monday Night
A 20 percent chance of rain before 11pm. Mostly cloudy, with a low around 42.
Tuesday
Mostly sunny, with a high near 59.
Tuesday Night
Partly cloudy, with a low around 44.
Wednesday
Mostly sunny, with a high near 62.
Wednesday Night
Mostly clear, with a low around 46.
Thursday
Sunny, with a high near 65.
Thursday Night
Mostly clear, with a low around 47.
Friday
Sunny, with a high near 64.

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: