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FXUS66 KMTR [Monterey CA] 201156 AFDMTR 

FXUS66 KMTR 201156
AFDMTR [HEAD]

National Weather Service San Francisco California 4:56am PDT Tue May 20 2025 

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
456 AM PDT TUE MAY 20 2025 [HEAD]

New aviation, marine.  

...NEW AVIATION, MARINE... [DISC]

Synopsis. Issued at 2:03am PDT Tuesday May 20 2025 

.SYNOPSIS...
ISSUED AT 203 AM PDT TUE MAY 20 2025 [DISC]

Strong and gusty northwesterly winds, above seasonal normal temperatures, and hazardous marine conditions today. Elevated fire weather conditions through Thursday. 

STRONG AND GUSTY NORTHWESTERLY WINDS, ABOVE SEASONAL NORMAL
TEMPERATURES, AND HAZARDOUS MARINE CONDITIONS TODAY. ELEVATED
FIRE WEATHER CONDITIONS THROUGH THURSDAY. [DISC]

Short term. (today and tonight) issued at 2:03am PDT Tuesday May 20 2025 

.SHORT TERM...
(TODAY AND TONIGHT)
ISSUED AT 203 AM PDT TUE MAY 20 2025 [DISC]

Heights will ever so slightly fall today as a subtle upper-level shortwave trough skirts the region, but temperatures will still remain seasonably warm. High pressure over the eastern Pacific Ocean and low pressure over the desert southwest will support a tight surface pressure gradient that will be conducive for northwesterly flow that will be locally strong over the waters, along the coastline, and through northwest/southeast oriented valleys such as the Salinas and Santa Clara. The return of onshore flow has allowed for cooler and moister conditions and subsequently the reformation of the marine layer, Albeit an interesting looking one as offshore/downslope flow in the higher terrain of the North Bay and Santa Cruz Mountains is resulting in compressional warming that's effectively wiping out the marine layer in those spots. Elevated fire weather conditions will be prevalent, primarily across the brush and grasses of the interior, through Thursday as dry and gusty conditions continue. 

HEIGHTS WILL EVER SO SLIGHTLY FALL TODAY AS A SUBTLE UPPER-LEVEL
SHORTWAVE TROUGH SKIRTS THE REGION, BUT TEMPERATURES WILL STILL
REMAIN SEASONABLY WARM. HIGH PRESSURE OVER THE EASTERN PACIFIC
OCEAN AND LOW PRESSURE OVER THE DESERT SOUTHWEST WILL SUPPORT A
TIGHT SURFACE PRESSURE GRADIENT THAT WILL BE CONDUCIVE FOR
NORTHWESTERLY FLOW THAT WILL BE LOCALLY STRONG OVER THE WATERS,
ALONG THE COASTLINE, AND THROUGH NORTHWEST/SOUTHEAST ORIENTED
VALLEYS SUCH AS THE SALINAS AND SANTA CLARA. THE RETURN OF ONSHORE
FLOW HAS ALLOWED FOR COOLER AND MOISTER CONDITIONS AND
SUBSEQUENTLY THE REFORMATION OF THE MARINE LAYER, ALBEIT AN
INTERESTING LOOKING ONE AS OFFSHORE/DOWNSLOPE FLOW IN THE HIGHER
TERRAIN OF THE NORTH BAY AND SANTA CRUZ MOUNTAINS IS RESULTING IN
COMPRESSIONAL WARMING THAT`S EFFECTIVELY WIPING OUT THE MARINE
LAYER IN THOSE SPOTS. ELEVATED FIRE WEATHER CONDITIONS WILL BE
PREVALENT, PRIMARILY ACROSS THE BRUSH AND GRASSES OF THE INTERIOR,
THROUGH THURSDAY AS DRY AND GUSTY CONDITIONS CONTINUE. [DISC]

Long term. (Wednesday through Monday) issued at 2:03am PDT Tuesday May 20 2025 

.LONG TERM...
(WEDNESDAY THROUGH MONDAY)
ISSUED AT 203 AM PDT TUE MAY 20 2025 [DISC]

A low amplitude upper-level shortwave ridge will nudge into the region Wednesday, bringing the warmest conditions of the week with temperatures of 10° above normal. Global ensemble clusters are all in agreement of heights falling through Friday due to an upper-level shortwave trough, which will translate to temperatures returning to seasonal normals by Friday as the brief, gradual cooling trend brings temperatures down by 5° each day. Agreement in global ensemble clusters continues with heights rebuilding Saturday as an upper-level shortwave ridge builds into the west, kicking off another brief, gradual warming trend. Oakland museum (oamc1) and San Francisco downtown (sfoc1) will put their daily minimum temperature records in jeopardy this week. Oakland museum (oamc1): Wednesday (5/21), Saturday (5/24), Sunday (5/25), and Monday (5/26), previous records of 49, 49, 49, and 50° respectively set in 1986, 2011, 1980, and 2008 respectively, the official forecast is 51, 51, 51, and 53° respectively. San Francisco downtown (sfoc1) on Friday (5/23) and Sunday (5/25), previous records of 47° set in 2010 and 1953 respectively, the official forecast is 50°. 

A LOW AMPLITUDE UPPER-LEVEL SHORTWAVE RIDGE WILL NUDGE INTO THE
REGION WEDNESDAY, BRINGING THE WARMEST CONDITIONS OF THE WEEK WITH
TEMPERATURES OF 10 DEGREES ABOVE NORMAL. GLOBAL ENSEMBLE CLUSTERS
ARE ALL IN AGREEMENT OF HEIGHTS FALLING THROUGH FRIDAY DUE TO AN
UPPER-LEVEL SHORTWAVE TROUGH, WHICH WILL TRANSLATE TO
TEMPERATURES RETURNING TO SEASONAL NORMALS BY FRIDAY AS THE BRIEF,
GRADUAL COOLING TREND BRINGS TEMPERATURES DOWN BY 5 DEGREES EACH
DAY. AGREEMENT IN GLOBAL ENSEMBLE CLUSTERS CONTINUES WITH HEIGHTS
REBUILDING SATURDAY AS AN UPPER-LEVEL SHORTWAVE RIDGE BUILDS INTO
THE WEST, KICKING OFF ANOTHER BRIEF, GRADUAL WARMING TREND.
OAKLAND MUSEUM (OAMC1) AND SAN FRANCISCO DOWNTOWN (SFOC1) WILL PUT
THEIR DAILY MINIMUM TEMPERATURE RECORDS IN JEOPARDY THIS WEEK.
OAKLAND MUSEUM (OAMC1): WEDNESDAY (5/21), SATURDAY (5/24), SUNDAY
(5/25), AND MONDAY (5/26), PREVIOUS RECORDS OF 49, 49, 49, AND 50
DEGREES RESPECTIVELY SET IN 1986, 2011, 1980, AND 2008
RESPECTIVELY, THE OFFICIAL FORECAST IS 51, 51, 51, AND 53 DEGREES
RESPECTIVELY. SAN FRANCISCO DOWNTOWN (SFOC1) ON FRIDAY (5/23) AND
SUNDAY (5/25), PREVIOUS RECORDS OF 47 DEGREES SET IN 2010 AND 1953
RESPECTIVELY, THE OFFICIAL FORECAST IS 50 DEGREES. [DISC]

Aviation. (12Z [5am PDT] TAFs [Terminal Aerodrome Forecasts]) issued at 4:40am PDT Tuesday May 20 2025 

.AVIATION...
(12Z TAFS)
ISSUED AT 440 AM PDT TUE MAY 20 2025 [AVIA]

VFR [Visual Flight Rules] is expected to prevail for all terminals from late this morning and through the evening hours. IFR [Instrument Flight Rules]/MVFR [Marginal Visual Flight Rules] ceilings over the Monterey Bay terminals are expected to lift by 18Z [11am PDT] this morning. Breezy NW/W winds will develop this afternoon for the coastal terminals, easing after sunset. 

VFR IS EXPECTED TO PREVAIL FOR ALL TERMINALS FROM LATE THIS
MORNING AND THROUGH THE EVENING HOURS. IFR/MVFR CEILINGS OVER THE
MONTEREY BAY TERMINALS ARE EXPECTED TO LIFT BY 18Z THIS MORNING.
BREEZY NW/W WINDS WILL DEVELOP THIS AFTERNOON FOR THE COASTAL
TERMINALS, EASING AFTER SUNSET. [AVI2]

Vicinity of SFO [San Francisco CA]… low marine stratus lingers in the vicinity of KSFO [San Francisco CA] and KOAK [Oakland CA] early this morning but is anchored to the immediate coastline and is not expected to impact the terminals directly. Breezy onshore winds this afternoon will ease after sunset. Low level marine stratus is expected to me more widespread late in the TAF [Terminal Aerodrome Forecast] period into the morning hours of Wednesday. 

VICINITY OF SFO...LOW MARINE STRATUS LINGERS IN THE VICINITY OF
KSFO AND KOAK EARLY THIS MORNING BUT IS ANCHORED TO THE IMMEDIATE
COASTLINE AND IS NOT EXPECTED TO IMPACT THE TERMINALS DIRECTLY.
BREEZY ONSHORE WINDS THIS AFTERNOON WILL EASE AFTER SUNSET. LOW
LEVEL MARINE STRATUS IS EXPECTED TO ME MORE WIDESPREAD LATE IN THE
TAF PERIOD INTO THE MORNING HOURS OF WEDNESDAY. [AVI2]

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

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

Monterey Bay terminals… LIFR [Low Instrument Flight Rules]/IFR [Instrument Flight Rules] ceilings have been steady overnight and are expected to lift by 17–18Z [10–11am PDT] this morning. Breezy onshore winds between 10–20 knots [12–23 mph] can be expected this afternoon, easing after sunset. Hires guidance indicates that IFR [Instrument Flight Rules]/LIFR [Low Instrument Flight Rules] marine stratus is likely to develop after midnight and persist through mid-morning Wednesday. 

MONTEREY BAY TERMINALS...LIFR/IFR CIGS HAVE BEEN STEADY OVERNIGHT
AND ARE EXPECTED TO LIFT BY 17-18Z THIS MORNING. BREEZY ONSHORE
WINDS BETWEEN 10-20 KNOTS CAN BE EXPECTED THIS AFTERNOON, EASING
AFTER SUNSET. HIRES GUIDANCE INDICATES THAT IFR/LIFR MARINE
STRATUS IS LIKELY TO DEVELOP AFTER MIDNIGHT AND PERSIST THROUGH
MID-MORNING WEDNESDAY. [AVI2]

Marine. (today through Sunday) issued at 4:40am PDT Tuesday May 20 2025 

.MARINE...
(TODAY THROUGH SUNDAY)
ISSUED AT 440 AM PDT TUE MAY 20 2025 [AVIA]

Widespread strong northerly breezes with gale force gusts are expected over the inner and outer waters today. Hazardous marine conditions will persist through Thursday with strong northwesterly breezes with gale force gusts and rough to very rough seas. 

WIDESPREAD STRONG NORTHERLY BREEZES WITH GALE FORCE GUSTS ARE
EXPECTED OVER THE INNER AND OUTER WATERS TODAY. HAZARDOUS MARINE
CONDITIONS WILL PERSIST THROUGH THURSDAY WITH STRONG NORTHWESTERLY
BREEZES WITH GALE FORCE GUSTS AND ROUGH TO VERY ROUGH SEAS. [AVI2]

MTR Watches/Warnings/Advisories

  • California: none.
  • Pacific Ocean: Small Craft Advisory until 9pm PDT this evening for Monterey Bay. 
.MTR WATCHES/WARNINGS/ADVISORIES...
CA...NONE.
PZ...SMALL CRAFT ADVISORY UNTIL 9 PM PDT THIS EVENING FOR MRY BAY. [WARN]
  • Gale Warning until 3am PDT Wednesday for Pigeon Pt [Pescadero CA] to Pt Pinos [Monterey CA] 0–10 nm [11 miles]-Pigeon Pt [Pescadero CA] to Pt Pinos [Monterey CA] 10–60 nm [69 miles]-Pt Arena [Mendocino CA] to Pt Reyes [San Francisco CA] 0–10 nm [11 miles]-Pt Arena [Mendocino CA] to Pt Reyes [San Francisco CA] 10–60 nm [69 miles]-Pt Pinos [Monterey CA] to Pt Piedras Blancas [San Simeon CA] 0–10 nm [11 miles]-Pt Reyes [San Francisco CA] to Pigeon Pt [Pescadero CA] 0–10 nm [11 miles]
     GALE WARNING UNTIL 3 AM PDT WEDNESDAY FOR PIGEON PT TO PT PINOS
0-10 NM-PIGEON PT TO PT PINOS 10-60 NM-PT ARENA TO PT REYES
0-10 NM-PT ARENA TO PT REYES 10-60 NM-PT PINOS TO PT
PIEDRAS BLANCAS 0-10 NM-PT REYES TO PIGEON PT 0-10 NM. [WRN2]
  • Short term…sarment long term…sarment aviation…JM marine…sarment 
SHORT TERM...SARMENT
LONG TERM....SARMENT
AVIATION...JM
MARINE...SARMENT [WRN2]
VISIT US AT WWW.WEATHER.GOV/SANFRANCISCO [LINK]

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Point Forecast

Half Moon Bay CA

20 May 05:35am PDT

Today Sunny, with a high near 61°. NW wind 7 to 17 mph, with gusts as high as 24 mph.
Tonight Mostly clear, with a low around 45°. NW wind 11 to 16 mph decreasing to 5 to 10 mph after midnight. Winds could gust as high as 25 mph.
Wednesday Sunny, with a high near 64°. WNW wind 5 to 13 mph.
Wednesday Night Partly cloudy, with a low around 46°. WNW wind 7 to 13 mph, with gusts as high as 21 mph.
Thursday Sunny, with a high near 60°. WNW wind 7 to 15 mph, with gusts as high as 24 mph.
Thursday Night Partly cloudy, with a low around 46°.
Friday Mostly sunny, with a high near 58°.
Friday Night Partly cloudy, with a low around 46°.
Saturday Mostly sunny, with a high near 61°.
Saturday Night Partly cloudy, with a low around 47°.
Sunday Mostly sunny, with a high near 60°.
Sunday Night Mostly cloudy, with a low around 48°.
Memorial Day Partly sunny, with a high near 60°.
Today
Sunny, with a high near 61. Northwest wind 7 to 17 mph, with gusts as high as 24 mph.
Tonight
Mostly clear, with a low around 45. Northwest wind 11 to 16 mph decreasing to 5 to 10 mph after midnight. Winds could gust as high as 25 mph.
Wednesday
Sunny, with a high near 64. West northwest wind 5 to 13 mph.
Wednesday Night
Partly cloudy, with a low around 46. West northwest wind 7 to 13 mph, with gusts as high as 21 mph.
Thursday
Sunny, with a high near 60. West northwest wind 7 to 15 mph, with gusts as high as 24 mph.
Thursday Night
Partly cloudy, with a low around 46.
Friday
Mostly sunny, with a high near 58.
Friday Night
Partly cloudy, with a low around 46.
Saturday
Mostly sunny, with a high near 61.
Saturday Night
Partly cloudy, with a low around 47.
Sunday
Mostly sunny, with a high near 60.
Sunday Night
Mostly cloudy, with a low around 48.
Memorial Day
Partly sunny, with a high near 60.

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: