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Area Forecast Discussion

FXUS66 KMTR [Monterey CA] 110901 AFDMTR 

FXUS66 KMTR 110901
AFDMTR [HEAD]

National Weather Service San Francisco Bay Area 2:01am PDT Tue Aug 11 2020 

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA
201 AM PDT TUE AUG 11 2020 [HEAD]

Synopsis. A slight cooling trend will continue today, especially across the interior. Meanwhile, little change is anticipated near the coast with the typical ebb and flow of low clouds each night/morning. A warming trend is forecast to begin on Wednesday and continue through the end of the week and into the weekend. 

.SYNOPSIS...A SLIGHT COOLING TREND WILL CONTINUE TODAY,
ESPECIALLY ACROSS THE INTERIOR. MEANWHILE, LITTLE CHANGE IS
ANTICIPATED NEAR THE COAST WITH THE TYPICAL EBB AND FLOW OF LOW
CLOUDS EACH NIGHT/MORNING. A WARMING TREND IS FORECAST TO BEGIN ON
WEDNESDAY AND CONTINUE THROUGH THE END OF THE WEEK AND INTO THE
WEEKEND. [DISC]

Discussion. As of 2:00am PDT Tuesday… coastal profilers at both Bodega Bay and Fort Ord indicate a slight deepening of the marine layer over the past 24 hours. In addition, onshore surface pressure gradients have increased. These developments are in response to an upper trough settling into the Pacific Northwest and weakening the ridge over California a bit. This process will continue today and result in another 3–7° of cooling, with most cooling expected across the interior. 

.DISCUSSION...AS OF 2:00 AM PDT TUESDAY...COASTAL PROFILERS AT
BOTH BODEGA BAY AND FORT ORD INDICATE A SLIGHT DEEPENING OF THE
MARINE LAYER OVER THE PAST 24 HOURS. IN ADDITION, ONSHORE SURFACE
PRESSURE GRADIENTS HAVE INCREASED. THESE DEVELOPMENTS ARE IN
RESPONSE TO AN UPPER TROUGH SETTLING INTO THE PACIFIC NORTHWEST
AND WEAKENING THE RIDGE OVER CALIFORNIA A BIT. THIS PROCESS WILL
CONTINUE TODAY AND RESULT IN ANOTHER 3 TO 7 DEGREES OF COOLING,
WITH MOST COOLING EXPECTED ACROSS THE INTERIOR. [DISC]

As the upper trough to our north shifts to the east on Wednesday, surface high pressure will build off the Northern California coast, resulting in a return to more typical northwesterly surface winds by Wednesday afternoon. These northwest winds may increase sufficiently by afternoon to sweep low clouds away from the coast north of the Golden Gate by late in the day. In addition, increasing north-to-south surface pressure gradients will limit onshore flow to some extent on Wednesday, which will result in the start of a warming trend for much of our area. 

AS THE UPPER TROUGH TO OUR NORTH SHIFTS TO THE EAST ON WEDNESDAY,
SURFACE HIGH PRESSURE WILL BUILD OFF THE NORTHERN CALIFORNIA
COAST, RESULTING IN A RETURN TO MORE TYPICAL NORTHWESTERLY SURFACE
WINDS BY WEDNESDAY AFTERNOON. THESE NORTHWEST WINDS MAY INCREASE
SUFFICIENTLY BY AFTERNOON TO SWEEP LOW CLOUDS AWAY FROM THE COAST
NORTH OF THE GOLDEN GATE BY LATE IN THE DAY. IN ADDITION,
INCREASING NORTH-TO-SOUTH SURFACE PRESSURE GRADIENTS WILL LIMIT
ONSHORE FLOW TO SOME EXTENT ON WEDNESDAY, WHICH WILL RESULT IN THE
START OF A WARMING TREND FOR MUCH OF OUR AREA. [DISC]

The warming trend is then expected to continue through the remainder of the week and into the upcoming weekend as an upper ridge over the desert southwest gradually expands west and northward across California. High temperatures in our warmest interior valleys will climb to around 100 by Friday, with additional warming possible over the weekend. Surface flow is forecast to remain onshore and thus coastal areas will experience less robust warming. But the marine layer will likely compress to a depth of less than 1000 feet by late in the week, allowing temperatures to warm into the 80s not all that far from the coast, while 90s will be common in the coastal valleys and hills by late in the week. Heat risk is currently projected to remain mostly in the moderate category, but scattered areas of high heat risk are projected in the interior valleys and hills by Friday and on into the weekend. 

THE WARMING TREND IS THEN EXPECTED TO CONTINUE THROUGH THE
REMAINDER OF THE WEEK AND INTO THE UPCOMING WEEKEND AS AN UPPER
RIDGE OVER THE DESERT SOUTHWEST GRADUALLY EXPANDS WEST AND
NORTHWARD ACROSS CALIFORNIA. HIGH TEMPERATURES IN OUR WARMEST
INTERIOR VALLEYS WILL CLIMB TO AROUND 100 BY FRIDAY, WITH
ADDITIONAL WARMING POSSIBLE OVER THE WEEKEND. SURFACE FLOW IS
FORECAST TO REMAIN ONSHORE AND THUS COASTAL AREAS WILL
EXPERIENCE LESS ROBUST WARMING. BUT THE MARINE LAYER WILL LIKELY
COMPRESS TO A DEPTH OF LESS THAN 1000 FEET BY LATE IN THE WEEK,
ALLOWING TEMPERATURES TO WARM INTO THE 80S NOT ALL THAT FAR
FROM THE COAST, WHILE 90S WILL BE COMMON IN THE COASTAL VALLEYS
AND HILLS BY LATE IN THE WEEK. HEAT RISK IS CURRENTLY PROJECTED TO
REMAIN MOSTLY IN THE MODERATE CATEGORY, BUT SCATTERED AREAS OF
HIGH HEAT RISK ARE PROJECTED IN THE INTERIOR VALLEYS AND HILLS BY
FRIDAY AND ON INTO THE WEEKEND. [DISC]

Remnant moisture from Hurricane Elida is forecast to be drawn northward around the western periphery of the desert southwest high and across the southern portion of our forecast area by late Thursday and Thursday night. This moisture plume is then forecast to lift northward across much of the rest of our forecast area by early in the weekend. Additional moisture from a second tropical system may then arrive over our area by early next week. Models do not generate precipitation over our area from this moisture, and the model blend currently keeps thunderstorm chances at less than 10%. In any case, this moisture and any possible mid-level instability will need to be monitored closely due to the potential for significant impacts if dry lightning were to develop. 

REMNANT MOISTURE FROM HURRICANE ELIDA IS FORECAST TO BE DRAWN
NORTHWARD AROUND THE WESTERN PERIPHERY OF THE DESERT SOUTHWEST
HIGH AND ACROSS THE SOUTHERN PORTION OF OUR FORECAST AREA BY LATE
THURSDAY AND THURSDAY NIGHT. THIS MOISTURE PLUME IS THEN FORECAST
TO LIFT NORTHWARD ACROSS MUCH OF THE REST OF OUR FORECAST AREA BY
EARLY IN THE WEEKEND. ADDITIONAL MOISTURE FROM A SECOND TROPICAL
SYSTEM MAY THEN ARRIVE OVER OUR AREA BY EARLY NEXT WEEK. MODELS DO
NOT GENERATE PRECIPITATION OVER OUR AREA FROM THIS MOISTURE, AND
THE MODEL BLEND CURRENTLY KEEPS THUNDERSTORM CHANCES AT LESS THAN
10 PERCENT. IN ANY CASE, THIS MOISTURE AND ANY POSSIBLE MID-LEVEL
INSTABILITY WILL NEED TO BE MONITORED CLOSELY DUE TO THE
POTENTIAL FOR SIGNIFICANT IMPACTS IF DRY LIGHTNING WERE TO
DEVELOP. [DISC]

Aviation. As of 11:00pm PDT Monday… for 06Z [11pm PDT] TAFs [Terminal Aerodrome Forecasts]. Stratus intrusion has brought IFR [Instrument Flight Rules] ceilings to most coastal terminals. Marine layer is currently around 1500 ft AGL [Above Ground Level] and continued deepening will likely bring lowering ceilings to inland terminals by early Tuesday morning. 

.AVIATION....AS OF 11:00 PM PDT MONDAY...FOR 06Z TAFS. STRATUS
INTRUSION HAS BROUGHT IFR CEILINGS TO MOST COASTAL TERMINALS.
MARINE LAYER IS CURRENTLY AROUND 1500 FT AGL AND CONTINUED
DEEPENING WILL LIKELY BRING LOWERING CEILINGS TO INLAND TERMINALS
BY EARLY TUESDAY MORNING. [AVIA]

Vicinity of KSFO [San Francisco CA]… currently VFR [Visual Flight Rules] with stratus being blocked by coastal mountains. MVFR [Marginal Visual Flight Rules]/IFR [Instrument Flight Rules] ceilings likely to develop beyond 10Z [3am PDT] Tuesday based on satellite imagery showing push of stratus around the SF Bay Area. Burnoff expected around 18Z [11am PDT] Tuesday. W/NW winds around 10 kt [12 mph] will persist but diminish slightly overnight. Continued onshore flow tomorrow afternoon with clearing skies. 

VICINITY OF KSFO...CURRENTLY VFR WITH STRATUS BEING BLOCKED BY
COASTAL MOUNTAINS. MVFR/IFR CEILINGS LIKELY TO DEVELOP BEYOND
10Z TUESDAY BASED ON SATELLITE IMAGERY SHOWING PUSH OF STRATUS
AROUND THE SF BAY AREA. BURNOFF EXPECTED AROUND 18Z TUESDAY. W/NW
WINDS AROUND 10 KT WILL PERSIST BUT DIMINISH SLIGHTLY OVERNIGHT.
CONTINUED ONSHORE FLOW TOMORROW AFTERNOON WITH CLEARING SKIES. [AVI2]

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

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

Monterey Bay terminals… IFR [Instrument Flight Rules] ceilings in place and probably lowering to LIFR [Low Instrument Flight Rules] overnight into early morning hours. Light to moderate NW winds easing overnight. Burnoff expected late morning or early afternoon. Continued onshore flow tomorrow afternoon with clearing skies. 

MONTEREY BAY TERMINALS...IFR CEILINGS IN PLACE AND PROBABLY
LOWERING TO LIFR OVERNIGHT INTO EARLY MORNING HOURS. LIGHT TO
MODERATE NW WINDS EASING OVERNIGHT. BURNOFF EXPECTED LATE MORNING
OR EARLY AFTERNOON. CONTINUED ONSHORE FLOW TOMORROW AFTERNOON WITH
CLEARING SKIES. [AVI2]

Marine. As of 09:41pm PDT Monday… southerly winds will switch to the west to northwest Tuesday night through Friday, remaining generally light. Mixed seas will continue through the period with a short period northwest swell and a longer period southerly swell. Southerly swell will increase Tuesday and Wednesday. 

.MARINE...AS OF 09:41 PM PDT MONDAY...SOUTHERLY WINDS WILL SWITCH
TO THE WEST TO NORTHWEST TUESDAY  NIGHT THROUGH FRIDAY, REMAINING
GENERALLY LIGHT. MIXED SEAS WILL  CONTINUE THROUGH THE PERIOD WITH
A SHORT PERIOD NORTHWEST SWELL  AND A LONGER PERIOD SOUTHERLY
SWELL. SOUTHERLY SWELL WILL INCREASE TUESDAY AND WEDNESDAY. [AVIA]

MTR Watches/Warnings/Advisories

.MTR WATCHES/WARNINGS/ADVISORIES...
.TDAY...SCA...SF BAY FROM 2 PM [WARN]

Public Forecast: Dykema; Aviation: Lorber/Canepa; Marine: Canepa 

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

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WWW.YOUTUBE.COM/NWSBAYAREA [DISC]

Point Forecast

Half Moon Bay CA

11 Aug 01:55am PDT

Overnight Mostly cloudy, with a low around 54°. SW wind around 9 mph.
Tuesday Cloudy, then gradually becoming mostly sunny, with a high near 64°. SW wind 8 to 10 mph.
Tuesday Night Mostly cloudy, with a low around 52°. WSW wind 7 to 10 mph.
Wednesday Mostly cloudy, with a high near 65°. SW wind 6 to 9 mph.
Wednesday Night Mostly cloudy, with a low around 52°. WSW wind 5 to 8 mph becoming calm in the evening.
Thursday Mostly sunny, with a high near 66°.
Thursday Night Mostly clear, with a low around 53°.
Friday Sunny, with a high near 70°.
Friday Night Patchy fog after 4am. Otherwise, mostly clear, with a low around 56°.
Saturday Patchy fog before 8am. Otherwise, sunny, with a high near 71°.
Saturday Night Patchy fog. Otherwise, mostly clear, with a low around 56°.
Sunday Patchy fog. Otherwise, sunny, with a high near 69°.
Sunday Night Mostly clear, with a low around 56°.
Monday Mostly sunny, with a high near 69°.
Overnight
Mostly cloudy, with a low around 54. Southwest wind around 9 mph.
Tuesday
Cloudy, then gradually becoming mostly sunny, with a high near 64. Southwest wind 8 to 10 mph.
Tuesday Night
Mostly cloudy, with a low around 52. West southwest wind 7 to 10 mph.
Wednesday
Mostly cloudy, with a high near 65. Southwest wind 6 to 9 mph.
Wednesday Night
Mostly cloudy, with a low around 52. West southwest wind 5 to 8 mph becoming calm in the evening.
Thursday
Mostly sunny, with a high near 66.
Thursday Night
Mostly clear, with a low around 53.
Friday
Sunny, with a high near 70.
Friday Night
Patchy fog after 4am. Otherwise, mostly clear, with a low around 56.
Saturday
Patchy fog before 8am. Otherwise, sunny, with a high near 71.
Saturday Night
Patchy fog. Otherwise, mostly clear, with a low around 56.
Sunday
Patchy fog. Otherwise, sunny, with a high near 69.
Sunday Night
Mostly clear, with a low around 56.
Monday
Mostly sunny, with a high near 69.

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: