697
FXUS66 KMTR 180313
AFDMTR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
813 PM PDT THU APR 17 2025
..NEW UPDATE
SYNOPSIS
ISSUED AT 228 PM PDT THU APR 17 2025
WARMING TREND KICKS OFF FRIDAY WITH NEAR SEASONAL HIGH
TEMPERATURES BUILDING INTO THE MID TO UPPER 70S BY EARLY NEXT
WEEK. BREEZY OFFSHORE WINDS ARE EXPECTED ACROSS INTERIOR MOUNTAINS
FRIDAY INTO EARLY SATURDAY (LOW IMPACT).
UPDATE
ISSUED AT 749 PM PDT THU APR 17 2025
SATELLITE IMAGERY SHOWS SOME INCREASES AND DECREASES IN THE
STRATUS THIS EVENING. SOME MODELS SHOW A MORE AGGRESSIVE PUSH
INLAND WITH OFFSHORE/NORTHERLY WINDS STARTING A LITTLE LATER.
THIS COULD IMPACT THE TEMPERATURE FORECAST FOR TOMORROW IF IT PANS
OUT AS CLOUDS COULD LINGER PAST MID TO LATE MORNING.
SHORT TERM
(THIS EVENING THROUGH FRIDAY)
ISSUED AT 228 PM PDT THU APR 17 2025
A FAIRLY DEEP MARINE LAYER ALLOWED FOR WIDESPREAD STRATUS TO EXTEND
THROUGHOUT THE BAY AREA AND INTO THE CENTRAL COAST. SATELLITE SHOWS
CLOUD COVER DISSIPATING OVER PORTIONS OF THE NORTH BAY BUT MUCH OF
THE REGION REMAINS SOCKED IN. THE SLOWER DISSIPATION OF CLOUD COVER
MAY RESULT IN TODAY'S HIGH TEMPERATURES STRUGGLING TO REACH THEIR
FORECASTED HIGHS. FOR EXAMPLE, THE FORECAST HIGH FOR SAN JOSE TODAY
IS 68 DEGREES WITH THE AIRPORT REPORTING 63 DEGREES AS OF 1PM. THIS
IS TRUE OF OTHER SITES WITH SFO REPORTING 56 DEGREES AS OF 1PM AND A
FORECAST HIGH OF 64 DEGREES OR LVK REPORTING 60 DEGREES AS OF 1PM
AND A FORECAST HIGH OF 68 DEGREES. THE DECIDING FACTOR WILL BE HOW
LONG IT TAKES FOR STRATUS TO CLEAR THIS AFTERNOON WITH PEAK HEATING
GENERALLY OCCURRING BETWEEN 3PM-4PM. STAY TUNED FOR TONIGHT'S UPDATE
TO SEE HOW TEMPERATURES FAIRED.
UPPER LEVEL TROUGHING WILL CONTINUE TO PROGRESS EASTWARD WITH UPPER
LEVEL RIDGING TO BUILD OVER THE WEST COAST TONIGHT INTO TOMORROW. AS
HIGH PRESSURE BUILDS, THE MARINE LAYER WILL START TO COMPRESS WITH
WRF GUIDANCE SHOWING IT COMPRESSING TO 1000-1500 FT OVERNIGHT. THIS
WILL LIMIT THE INLAND SPREAD OF STRATUS TONIGHT. THIS MORNING, THE
INLAND INTRUSION OF STRATUS BROUGHT WITH IT MUCH MORE MOIST AIR
WHICH RESULTED IN WIDESPREAD DRIZZLE TO LIGHT RAIN ACROSS THE COAST
AND ELEVATED TERRAIN WHERE OROGRAPHIC UPLIFT WAS FAVORED. DRIZZLE IS
NOT EXPECTED TO BE AS WIDESPREAD TONIGHT INTO TOMORROW MORNING WITH
GUIDANCE SHOWING DRIER CONDITIONS OFFSHORE AND KEEPING HIGHER PWAT
VALUES (0.5"-0.7") GENERALLY IN THE MONTEREY BAY REGION. FOR NOW,
KEPT TOMORROW MORNINGS DRIZZLE CHANCES CONFINED TO THE MONTEREY BAY
REGION BUT MAY NEED TO EXPAND DRIZZLE CHANCES NORTHWARD ALONG THE
COASTLINE.
LONG TERM
(FRIDAY NIGHT THROUGH NEXT WEDNESDAY)
ISSUED AT 228 PM PDT THU APR 17 2025
A WARMING TREND IS EXPECTED TO KICK OFF FRIDAY WITH TEMPERATURES
BECOMING MORE SEASONAL TO SLIGHTLY ABOVE NORMAL ACROSS THE INTERIOR
AS HIGH PRESSURE BUILDS. TEMPERATURES WILL WARM INTO THE LOW TO MID
70S ON FRIDAY AND SATURDAY WITH TEMPERATURES TO BUILD INTO THE MID
TO UPPER 70S SUNDAY INTO TUESDAY. AS TEMPERATURES BUILD, MINOR
HEATRISK WILL SPREAD ACROSS URBAN AREAS OF THE BAY AREA AND CENTRAL
COAST FRIDAY THROUGH TUESDAY. MINOR HEATRISK GENERALLY ONLY IMPACTS
INDIVIDUALS WHO ARE EXTREMELY SENSITIVE TO HEAT OR WITHOUT ADEQUATE
COOLING/HYDRATION. WHILE TEMPERATURES ARE FORECAST TO PEAK IN THE
MID TO UPPER 70S, REMEMBER TO LISTEN TO YOUR BODY AND DRINK PLENTY
OF WATER/TAKE BREAKS AS NEEDED WHILE OUTDOORS AS WE TRANSITION FROM
THE COOLER SEASONS TO THE WARMER SEASONS.
OFFSHORE WINDS ARE EXPECTED TO DEVELOP FRIDAY AS HIGH PRESSURE
BUILDS ACROSS THE WEST COAST AND UPPER LEVEL TROUGHING DEEPENS OVER
THE INTERMOUNTAIN WEST. UPPER LEVEL SUPPORT STILL LOOKS MINIMAL WITH
THE 500MB AND 200MB JET STREAMS CENTERED TO OUR EAST OVER THE
CALIFORNIA-NEVADA BORDER AND THE 850 MB JET STREAM CENTERED OFFSHORE
OVER THE OCEAN. THE LACK OF UPPER SUPPORT WILL WEAKEN OFFSHORE FLOW
WITH OFFSHORE WINDS TO PEAK BETWEEN 20-30 MPH ACROSS THE ELEVATED
TERRAIN (PRIMARILY NORTH BAY INTERIOR MOUNTAINS AND EAST BAY
HILLS). PROBABILISTIC GUIDANCE SHOWS A LOW (<10%) CHANCE FOR GUSTS
BETWEEN 30 TO 35 MPH ACROSS FAR NORTHERN NAPA AND SONOMA COUNTIES
ON FRIDAY. WE WILL SEE SOME WARMING AND DRYING ACROSS THE REGION
THIS WEEK BUT FIRE CONCERNS REMAIN MINIMAL WITH FUELS STILL
DECENTLY MOIST FROM THIS PAST WINTER. OFFSHORE WINDS WILL DIMINISH
AND SHIFT ONSHORE AGAIN OVERNIGHT FRIDAY INTO SATURDAY AS UPPER
LEVEL RIDGING BUILDS OVER THE WEST COAST AND UPPER LEVEL TROUGHING
MOVES INTO THE CENTRAL UNITED STATES.
HEADING INTO NEXT WEDNESDAY THE FORECAST BECOMES A LITTLE MORE
UNCERTAIN. DETERMINISTIC ECMWF GUIDANCE SHOWS AN UPPER LEVEL TROUGH
MOVING INTO THE WEST COAST MID TO LATE NEXT WEEK. IN TERMS OF
PROBABILISTIC CLUSTER GUIDANCE, MODELS ARE NOT IN AGREEMENT AS TO
HOW DEEP THIS TROUGH WILL BE OR WHERE IT WILL SET UP. THE CURRENT
FORECAST SHOWS TEMPERATURES COOLING BACK INTO THE UPPER 60S TO LOW
70S STARTING WEDNESDAY, BUT, THIS COOLING TREND IS DEPENDENT ON
WHERE THE TROUGH SETS UP AND HOW DEEP IT IS.
AVIATION
(00Z TAFS)
ISSUED AT 439 PM PDT THU APR 17 2025
MVFR STRATUS PERSISTS OVER THE BAY AREA AND MONTEREY BAY REGION,
WITH PARTIAL CLEARING OVER THE NORTH BAY AND SOUTHERN MONTEREY
COUNTY. A DISTINCT BOUNDARY, WHERE STRATUS MIXES OUT TO THE NORTH
AND PERSISTS TO THE SOUTH, IS PASSING SFO AND OAK. MONITORING THE
DEVELOPMENT OF THIS BOUNDARY AS IT RELATES TO THE SHORT-TERM CEILING
FORECAST. IN ANY CASE, MVFR STRATUS SHOULD PERSIST IN THE SOUTH BAY
AND MONTEREY BAY REGIONS THROUGH THE EVENING, WITH SOME CHANCES OF
IFR-LIFR CEILINGS DEVELOPING AT THE IMMEDIATE COAST OVERNIGHT. LOW
TO MODERATE CONFIDENCE IN CLEARING TIMES ON FRIDAY MORNING, WITH
MOST TERMINALS CLEARING OUT RATHER LATE. SOME MODELS KEEP THE
IMMEDIATE COAST AND THE MONTEREY BAY REGION SOCKED IN THROUGH THE
TAF PERIOD. BREEZY ONSHORE FLOW SHOULD CONTINUE THROUGH THIS EVENING
AND DOMINATE FRIDAY AFTERNOON AND EVENING. AFTER THE END OF THE TAF
PERIOD, A COMPRESSING MARINE LAYER SHOULD RESULT IN LESS EXTENSIVE,
BUT LOWER CEILING, STRATUS INTO SATURDAY MORNING.
VICINITY OF SFO... MVFR CEILINGS PERSIST AT THE TERMINAL. MONITORING
THE PASSING OF A BOUNDARY TO SEE IF IT CLEARS OUT THE CEILINGS, IN
WHICH CASE STRATUS WOULD RETURN IN THE LATE EVENING. OTHERWISE
THE CLOUDS PERSIST INTO THE EVENING AND OVERNIGHT. CURRENT
FORECAST HAS THE CLOUDS SCATTERING OUT EARLY FRIDAY AFTERNOON WITH
BREEZY WEST- NORTHWEST WINDS. SOME MODEL OUTPUT HAS CEILINGS
RETURNING AS EARLY AS 2-3Z ON FRIDAY AFTERNOON, BUT IT IS A LOW
CONFIDENCE FORECAST AT THIS TIME AND HAVE OPTED TO KEEP CEILINGS
OUT OF THE CURRENT TAF.
SFO BRIDGE APPROACH... SIMILAR TO SFO. IF THE BOUNDARY CLEARS OUT
THE STRATUS, EXPECT THE APPROACH TO CLEAR OUT A LITTLE LATER THAN AT
THE TERMINAL.
MONTEREY BAY TERMINALS... MVFR CEILINGS CONTINUE THROUGH THE EVENING
AND OVERNIGHT HOURS, WITH LOW TO MODERATE CONFIDENCE OF IFR-LIFR
CONDITIONS EARLY FRIDAY MORNING. TOWARDS THE END OF THE TAF PERIOD,
UNCERTAINTY INCREASES WITH MODELS DIVERGING ON WHETHER THE CEILINGS
WILL CLEAR OR NOT. HAVE OPTED TO RETAIN THE CURRENT FORECAST WHERE
CEILINGS DO SCATTER OUT, BUT WILL KEEP AN EYE ON UPDATED MODEL DATA.
MODELS POINT TO A POSSIBLE EARLY RETURN OF STRATUS RIGHT AT, OR
SHORTLY AFTER, THE END OF THE TAF PERIOD.
MARINE
(TONIGHT THROUGH NEXT TUESDAY)
ISSUED AT 439 PM PDT THU APR 17 2025
MODERATE TO FRESH NORTHERLY BREEZE ACROSS THE OUTER COASTAL
WATERS WITH LIGHT AND VARIABLE WINDS CLOSER TO THE COAST. AS THE
WINDS DIMINISH, ROUGH SEAS WILL SUBSIDE TONIGHT THROUGH FRIDAY
BEFORE ANOTHER STRONG BREEZE REBUILDS SEAS THIS WEEKEND WHICH WILL
LIKELY PERSIST INTO EARLY NEXT WEEK.
MTR WATCHES/WARNINGS/ADVISORIES
CA...NONE.
PZ...SMALL CRAFT ADVISORY FROM 9 PM FRIDAY TO 9 AM PDT SATURDAY FOR
PT ARENA TO PT REYES 10-60 NM.
SHORT TERM...KENNEDY
LONG TERM....KENNEDY
AVIATION...DIALH
MARINE...DIALH
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