674
FXUS66 KMTR 101951
AFDMTR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
1251 PM PDT THU JUL 10 2025
..NEW SHORT TERM, LONG TERM
KEY MESSAGES
UPDATED AT 1208 PM PDT THU JUL 10 2025
- INLAND TEMPERATURES ROUGHLY 10 DEGREES WARMER THAN YESTERDAY,
BRINGING MODERATE HEATRISK THROUGH FIRDAY.
- LOCALIZED ELEVATED FIRE WEATHER THREAT CONTINUES ACROSS HIGHER
ELEVATIONS.
- GRADUAL COOLING TREND NEXT WEEK.
SHORT TERM
ISSUED AT 1208 PM PDT THU JUL 10 2025
(THIS EVENING THROUGH FRIDAY)
BYRON AIRPORT IN FAR EATSTERN CONTRA COSTA COUNTY CROSSED INTO
THE 90S BY NOON, BUT MOST INLAND STATIONS ARE STILL REPORTING 70S
AND LOW 80S. SOME SMOKE IS PROPAGATING INTO THE REGION, MAINLY
FROM THE GREEN FIRE IN SHASTA COUNTY. THIS WILL FILTER AND REFLECT
SOME OF THE SUNLIGHT AND SHOULD TAKE THE EDGE OFF THE HEAT TODAY.
OUR LATEST SHORT TERM FORECAST KEEPS THE WARMEST AREAS GENERALLY
IN THE MID 90S BOTH TODAY AND FRIDAY. WHILE THESE TEMPERATURES ARE
ONLY 5-10 DEGREES ABOVE NORMAL, IT MAY FEEL WORSE THAN THAT SINCE
WE JUST FINISHED A COOL PERIOD. COASTAL AREAS WILL STAY IN THE 60S
AND 70S THANKS TO ONSHORE WIND. THE MARINE LAYER HAS COMPRESSED
TO 1,000 FEET, WHICH WILL KEEP OVERNIGHT CLOUDS CONFINED CLOSER TO
THE COAST AND THEY SHOULD EVAPORATE FASTER THAN NORMAL FRIDAY
MORNING.
LONG TERM
ISSUED AT 1208 PM PDT THU JUL 10 2025
(FRIDAY NIGHT THROUGH NEXT WEDNESDAY)
THERE IS HIGH CONFIDENCE THAT THE PATTERN WILL REMAIN FAIRLY
STABLE THROUGH EARLY NEXT WEEK WITH HIGH PRESSURE ANCHORED NEAR
THE CHANNEL ISLANDS, EMBEDDED IN BROAD HIGH PRESSURE ACROSS THE
EASTERN PACIFIC. WHILE THIS HIGH PRESSURE WILL CAUSE THE 850 TEMP
TO BUILD TO THE 90TH PERCENTILE FOR MID-JULY, WE ARE ACTUALLY
GOING TO COOL OFF A BIT THIS WEEKEND. THE OVERALL PATTERN SUPPORTS
ONSHORE WIND. WITH HIGH PRESSURE OFFSHORE AND TO OUR SOUTH, BOTH
DOWNGRADIENT AND GEOSTRPHIC WINDS ARE ONSHORE. THIS SYNOPTIC
FORCING IS ENHANCED EACH DAY AS THE THERMAL TROUGH OVER THE
CENTRAL VALLEY DEEPENS. THE PRESSURE GRADIENT FROM SFO TO SAC IS
EXPECTED TO FLUCTUATE FROM +1 MB AT NIGHT TO +4 MB DURING THE DAY
THROUGH EARLY NEXT WEEK. THIS HAPPENS BECAUSE THE RIDGE BRINGS
AFTERNOON TEMPERATURES AROUND 100 DEGREES IN THE CENTRAL VALLEY.
THIS HOT AIR RISES AND LITERALLY LIFTS A WEIGHT OFF THE LOWER
ATMOSPHERE. THIS INDUCED LOW PRESSURE THEN PULLS IN AIR FROM THE
BAY AREA LIKE A VACUUM. WITH OCEAN WATERS IN THE MID-50S, THE
ONSHORE WINDS ACT AS A NATURAL AIR CONDITIONING, KEEPING US MUCH
COOLER. BY THE MIDDLE OF NEXT WEEK, IT LOOKS LIKE A TROUGH WILL
DISRUPT THE PATTERN AND COOL THINGS OFF ACROSS THE STATE. IN THE
SUPER-LONG RANGE, THERE IS SOME INDICATION THAT A 4-CORNERS HIGH
WILL START TO BUILD AROUND JULY 22-24, WHICH COULD BRING MORE
IMPACTFUL HEAT LATE IN THE MONTH.
AVIATION
(18Z TAFS)
ISSUED AT 1021 AM PDT THU JUL 10 2025
CURRENTLY VFR AT ALL TERMINALS WITH THE EXCEPTION OF HAF. STRATUS
WILL STICK TO THE COAST TODAY WITH A SIMILAR FORECAST ON TAP FOR
TONIGHT AS WHAT OCCURRED LAST NIGHT WITH THE PATTERN LARGELY
REMAINING UNCHANGED UNDER THE INFLUENCE OF HIGH PRESSURE. AS SUCH,
MOST TERMINALS WILL BE ON THE RECEIVING END OF LIFR-IFR CEILINGS AS
SUBSIDENCE ALOFT CONTINUES TO SUPPORT A COMPRESSED MARINE LAYER.
VICINITY OF SFO...CURRENTLY VFR WITH NORTHWESTERLY FLOW. WINDS WILL
BACK THROUGH THE MORNING, BECOMING WESTERLY WHEN THE AFTERNOON SEA
BREEZE KICKS IN. LOW TO MODERATE CONFIDENCE IN THE FORECAST FOR
TONIGHT. IF A SUB-VFR CEILING WERE TO DEVELOP, IT IS LIKELY THAT IT
WOULD BE IFR. HREF DEPICTS A DONUT HOLE OVER SFO TONIGHT, SO FOR NOW
HAVE TRENDED IN A LATER ARRIVAL TIME WITH SHORTER DURATION AND A BKN
CEILING INSTEAD OF OVC. A REASONABLE BEST CASE SCENARIO WOULD BE
THAT THE MARINE LAYER IS TOO COMPRESSED TO PENETRATE THROUGH THE SAN
BRUNO GAP AND THE TERMINAL REMAINS VFR.
SFO BRIDGE APPROACH...SIMILAR TO SFO.
MONTEREY BAY TERMINALS...CURRENTLY VFR WITH WESTERLY WINDS AT BOTH
TERMINALS. HIGH CONFIDENCE IN LIFR CEILINGS RETURNING TO BOTH
TERMINALS TONIGHT.
MARINE
(TODAY THROUGH TUESDAY)
ISSUED AT 423 AM PDT THU JUL 10 2025
MODERATE TO STRONG WINDS PERSIST TODAY WITH GALE STRENGTH
EXPECTED FOR THE NORTHERN OUTER WATERS LATE TONIGHT INTO EARLY
FRIDAY. EXPECT BUILDING ROUGH SEAS IN THE EXPOSED WATERS ALONGSIDE
THE BUILDING WINDS. SEAS AND WINDS WILL BEGIN TO SLACK INTO THE
WEEKEND.
MTR WATCHES/WARNINGS/ADVISORIES
CA...NONE.
PZ...SMALL CRAFT ADVISORY UNTIL 3 AM PDT FRIDAY FOR PT ARENA TO PT
REYES 0-10 NM.
SMALL CRAFT ADVISORY UNTIL 9 PM PDT THIS EVENING FOR PT PINOS TO
PT PIEDRAS BLANCAS 0-10 NM.
SMALL CRAFT ADVISORY UNTIL 3 PM PDT THIS AFTERNOON FOR PT ARENA
TO PT REYES 10-60 NM.
GALE WARNING UNTIL 9 AM PDT FRIDAY FOR PT ARENA TO PT REYES 10-
60 NM.
SMALL CRAFT ADVISORY UNTIL 9 AM PDT FRIDAY FOR PIGEON PT TO PT
PINOS 10-60 NM.
SHORT TERM...FLYNN
LONG TERM....FLYNN
AVIATION...SARMENT
MARINE...SARMENT
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