827
FXUS66 KMTR 190457
AFDMTR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
957 PM PDT MON AUG 18 2025
..NEW AVIATION, MARINE
KEY MESSAGES
UPDATED AT 245 PM PDT MON AUG 18 2025
- WARMING TREND INTO THE WEEKEND
- MODERATE HEATRISK FOR THE INTERIOR THURSDAY-SATURDAY
- SEE HEAT SAFETY TIPS BELOW
UPDATE
ISSUED AT 940 PM PDT MON AUG 18 2025
CLOUDS HAVE BEEN SLOWER TO RETURN THAN EARLIER MODELS HAD
INDICATED THIS EVENING. THE NBM 25TH PERCENTILE EVEN SHOWS CLOUDS
SHOULD BE ALONG THE SAN MATEO COAST AND LOOKING AT COASTAL WEB
CAMS, THERE'S NOTHING. DID A QUICK UPDATE TO THE SKY GRIDS TO SHOW
LESS COVERAGE THAN ORIGINALLY IN THE FORECAST, BUT EVEN THE UPDATE
MAY BE TOO MUCH. CLOUDS OFFSHORE ARE CONTINUING TO ERODE AS THEY
ENCOUNTER THE DRIER AIR THAT HAS DOMINATED THE REGION TODAY. WHILE
THERE REMAINS A SHOT AT COASTAL CLOUDS WORKING THEIR WAY BACK IN,
IT WILL BE SHORT LIVED, LOCALIZED, AND LIKELY BE A SUNRISE
SURPRISE. OTHER THAN THAT, THE EVENING AND OVERNIGHT FORECAST IS
IN RANGE AND HAS BEEN LEFT ALONE. ENJOY YOUR STARRY NIGHT.
SHORT TERM
ISSUED AT 245 PM PDT MON AUG 18 2025
(THIS EVENING THROUGH TUESDAY)
CLEAR SKIES AND WARMER TEMPERATURES THAN WE'VE SEEN THE PAST COUPLE
OF DAYS HAVE MADE FOR A BEAUTIFUL DAY ACROSS OUR AREA. A WEAK FETCH
OF OFFSHORE FLOW TODAY ACROSS PORTIONS OF THE CENTRAL COAST HAS
RESULTED IN A BUMP IN DAYTIME HIGHS THROUGH THE SALINAS VALLEY AND
MONTEREY PENINSULA. LOW STRATUS HAS ERODED AND SHOULD MAKE FOR A
WONDERFUL SUNSET UP AND DOWN OUR COASTLINE LATER THIS EVENING. A
COMPRESSED MARINE LAYER WILL LIMIT STRATUS COVERAGE DURING THE
OVERNIGHT INTO EARLY TUESDAY MORNING, KEEPING IT MOSTLY CONFINED
TO THE IMMEDIATE COASTLINE WHERE STRATUS DOES DEVELOP. IT SHOULD
BE A GREAT NIGHT TO WATCH THE SUNSET, FOLLOWED BY THE PERSEID
METEOR SHOWER.
LONG TERM
ISSUED AT 245 PM PDT MON AUG 18 2025
(TUESDAY NIGHT THROUGH NEXT SUNDAY)
A GRADUAL WARMUP FOR THE FIRST HALF OF THE WORK WEEK WILL ACCELERATE
FOR THURSDAY AND FRIDAY, AND THEN GRADUALLY EASE INTO THE WEEKEND. A
BUILDING DOME OF HIGH PRESSURE WILL BEGIN TO CENTER AROUND THE FOUR
CORNERS AREA TUESDAY, THEN EXPAND WESTWARD FOR THE SECOND HALF OF
THE WORK WEEK. CONSENSUS IN THE SYNOPTIC PATTERN IS GOOD THROUGH
FRIDAY, PROVIDING HIGH CONFIDENCE FOR AREAS OF MODERATE HEATRISK
ACROSS MUCH OF OUR INTERIOR THURSDAY THROUGH SATURDAY. CONSENSUS IN
DETERMINISTIC GUIDANCE BEGINS TO BREAKDOWN FOR THE WEEKEND INTO THE
BEGINNING OF NEXT WEEK. IT IS TOO SOON TO KNOW WHETHER THE
PERSISTENT TROUGHING TO OUR WEST THAT WE'VE SEEN MOST OF THE SUMMER
WILL WIN OUT OVER THE EXPANDING RIDGE AS WE HEAD INTO THE WEEKEND
AND INTO THE BEGINNING OF NEXT WEEK. IF THE RIDGING BECOMES THE
DOMINANT SYNOPTIC INFLUENCE WE MAY SEE A LONGER PERIOD OF MODERATE
HEATRISK THROUGH THE EXTENDED FORECAST, WHICH WOULD HAVE
COMPOUNDING IMPACTS. NOW IS THE TIME TO BEGIN TO BE AWARE AND
PREPARE FOR UPCOMING HEAT IMPACTS.
HEAT SAFETY TIPS:
HEAT IS THE NUMBER 1 WEATHER RELATED KILLER IN THE UNITED STATES.
FOLLOW THESE TIPS TO PROTECT YOURSELF, YOUR LOVED ONES, AND YOUR
ANIMALS.
-STAY INSIDE IN AN AIR CONDITIONED ENVIRONMENT BETWEEN 10AM AND 7PM.
-SUSPEND UNNECESSARY OUTDOOR ACTIVITIES DURING MODERATE HEAT, BUT
IF YOU MUST BE OUTDOORS, TAKE FREQUENT BREAKS IN THE SHADE OR AC
AND DRINK COOL WATER.
-KNOW THE SIGNS AND SYMPTOMS OF HEAT EXHAUSTION VS. HEAT STROKE!
HEAT STROKE CAN BE DEADLY IF NOT TREATED IMMEDIATELY BY A MEDICAL
PROFESSIONAL. CALL 911 IF YOU SUSPECT SOMEONE IS SUFFERING FROM HEAT
STROKE.
-WEAR A LIFE JACKET, SWIM NEAR A LIFEGUARD, AND CHECK CONDITIONS
BEFORE ENTERING THE WATER IF GOING TO A RIVER OR OCEAN TO COOL OFF.
RIVERS AND THE OCEAN ARE EXTREMELY COLD, AND COLD WATER SHOCK CAN
TURN INTO PARALYSIS AND DROWNING IF YOU ARE NOT CAREFUL.
-USE A COOL AND DAMP TOWEL ON YOUR BODY IF YOU DO NOT HAVE AC AND
ARE FEELING HOT. OR, TAKE A COOL SHOWER OR BATH.
-DO NOT LEAVE KIDS OR PETS IN A PARKED CAR.
-ENSURE PETS AND LIVESTOCK HAVE ACCESS TO SHADE AND WATER.
AVIATION
(06Z TAFS)
ISSUED AT 957 PM PDT MON AUG 18 2025
SATELLITE SHOWS CLEAR SKIES ACROSS THE REGION WITH CONFIDENCE
DIMINISHING THAT WIDESPREAD STRATUS WILL RETURN TONIGHT. CURRENT
THINKING IS THAT THE COMPRESSED MARINE LAYER AND DRIER AIR MASS WILL
MAKE IT HARDER FOR STRATUS TO REDEVELOP ACROSS THE BAY AREA TONIGHT
GIVEN THE CURRENT LACK OF CLOUD COVER ACROSS THE ADJACENT MARINE
ZONES. THAT BEING SAID, THERE IS STILL A CHANCE EARLY TOMORROW
MORNING FOR OAK AND HAF TO SEE SOME STRATUS, AT LEAST TEMPORARILY,
AROUND SUNRISE. THE ONLY OTHER SITES WITH EVEN A LOW END POTENTIAL
FOR STRATUS ARE MRY AND SNS. WINDS GENERALLY STAY ONSHORE THROUGH
THE TAF PERIOD WITH LOCALLY BREEZY WINDS TO DEVELOP AT SFO DURING
THE AFTERNOON/EVENING HOURS.
VICINITY OF SFO...VFR. A DRIER AIR MASS AND COMPRESSED MARINE LAYER
WILL KEEP ANY STRATUS THAT IS ABLE TO DEVELOP AWAY FROM SFO TONIGHT.
THERE IS A LOW (~30%) CHANCE THAT STRATUS WILL DEVELOP AROUND
SUNRISE TOMORROW MORNING WITHIN THE 13Z-17Z AS THE MOST LIKELY
TIMEFRAME. THE MORE LIKELY SCENARIO IS THAT PATCHY STRATUS WILL
DEVELOP IN THE VICINITY OF OAK AND ACROSS PORTIONS OF THE SF BAY BUT
NOT IMPACT THE AIRPORT ITSELF. WINDS WILL REMAIN GUSTY DURING THE
AFTERNOON AND EVENING HOURS WITH GUSTS TO AROUND 25 KNOTS EXPECTED.
SFO BRIDGE APPROACH...PATCHY STRATUS MAY IMPACT THE BRIDGE APPROACH
EARLY TOMORROW MORNING WITH HIGHEST POTENTIAL DURING THE 13Z-18Z
TIMEFRAME. OTHERWISE, SIMILAR TO SFO.
MONTEREY BAY TERMINALS...VFR. CONFIDENCE IS DECREASING THAT STRATUS
WILL DEVELOP AT MRY AND SNS TONIGHT. LAMP, MOS, AND HRRR GUIDANCE
HAVE ALL TRENDED DOWNWARDS AS TO THE AMOUNT OF STRATUS COVERAGE WITH
EVEN THE NAMNEST (TYPICALLY THE MOST MOIST) MODEL SHOWING CLEAR
SKIES OVER THE MONTEREY PENINSULA TONIGHT. IF ANY STRATUS DOES
DEVELOP IT IS NOT LIKELY TO OCCUR UNTIL AFTER 12Z AND AROUND
SUNRISE. THERE IS A SLIGHTLY HIGHER CHANCE FOR STRATUS TO DEVELOP AT
MRY THAN AT SNS. WINDS GENERALLY REMAIN ONSHORE THROUGH THE TAF
PERIOD WITH WINDS BETWEEN 10 TO 15 KNOTS EXPECTED DURING THE DAY.
MARINE
(TONIGHT THROUGH NEXT SUNDAY)
ISSUED AT 957 PM PDT MON AUG 18 2025
WINDS INCREASE MIDWEEK AS THE PRESSURE GRADIENT TIGHTENS WITH A
FRESH TO STRONG NORTHWEST BREEZE DEVELOPING OVER THE OUTER WATERS
AND PORTIONS OF THE INNER WATERS. ROUGH SEAS WILL BUILD ACROSS THE
OUTER WATERS MID TO LATE WEEK BEFORE SEAS SUBSIDE AND WINDS
DIMINISH OVER THIS WEEKEND. FRESH TO STRONG GUSTS ARE EXPECTED TO
DEVELOP ACROSS THE SAN FRANCISCO BAY EACH AFTERNOON AND EVENING.
MTR WATCHES/WARNINGS/ADVISORIES
CA...NONE.
PZ...SMALL CRAFT ADVISORY FROM 3 PM TO 9 PM PDT TUESDAY FOR MRY BAY-
PIGEON PT TO PT PINOS 0-10 NM.
SMALL CRAFT ADVISORY UNTIL 3 AM PDT TUESDAY FOR PT PINOS TO PT
PIEDRAS BLANCAS 0-10 NM.
SMALL CRAFT ADVISORY FROM 3 PM TUESDAY TO 9 AM PDT WEDNESDAY FOR
PT PINOS TO PT PIEDRAS BLANCAS 0-10 NM.
SMALL CRAFT ADVISORY FROM 9 PM TUESDAY TO 9 AM PDT WEDNESDAY FOR
PIGEON PT TO PT PINOS 10-60 NM-PT ARENA TO PT REYES 10-60
NM.
SHORT TERM...JM
LONG TERM....JM
AVIATION...KENNEDY
MARINE...KENNEDY
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