759
FXUS66 KMTR 180534
AFDMTR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
1034 PM PDT THU APR 17 2025
..NEW AVIATION, MARINE
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
(06Z TAFS)
ISSUED AT 1033 PM PDT THU APR 17 2025
SCATTERED MVFR STRATUS REMAINS OVER PARTS OF THE BAY AREA WITH MORE
EXTENSIVE STRATUS COVERAGE IN THE CENTRAL COAST. STRATUS EVOLUTION
HAS BEEN DIFFICULT TO FORECAST TODAY, AND MODEL INDICATIONS ARE THAT
THE DIFFICULTY WILL CONTINUE INTO THE OVERNIGHT AND MORNING PERIODS.
THE CURRENT FORECAST CALLS FOR MVFR STRATUS TO EXPAND ACROSS THE BAY
AREA TONIGHT, WITH IFR-LIFR STRATUS POSSIBLE AT THE IMMEDIATE COAST.
STRATUS SHOULD DISSIPATE THROUGH FRIDAY MORNING, WITH LOW TO
MODERATE CONFIDENCE ON THE EXACT TIME. ALONG THE IMMEDIATE COAST,
MODELS DISAGREE ON WHETHER THERE WILL BE PERIODS OF CLEAR SKIES OR
WHETHER THE TERMINALS WILL BE SOCKED IN THROUGH THE TAF PERIOD.
BREEZY ONSHORE FLOW WILL DOMINATE FRIDAY AFTERNOON AND EVENING. A
COMPRESSING MARINE LAYER SHOULD RESULT IN LESS EXTENSIVE, BUT LOWER
CEILING, STRATUS FRIDAY NIGHT INTO SATURDAY MORNING.
VICINITY OF SFO... THE TERMINAL SHOULD REMAIN VFR THROUGH THE
EVENING HOURS AND MVFR CEILINGS WILL RETURN NEAR MIDNIGHT. CURRENT
FORECAST HAS THE CLOUDS SCATTERING OUT EARLY FRIDAY AFTERNOON WITH
BREEZY WEST-NORTHWEST WINDS. LOW CONFIDENCE FOR ANY STRATUS
DEVELOPMENT OVER THE TERMINAL FRIDAY NIGHT, BUT WILL MONITOR
CONDITIONS GIVEN THE FORECASTING CHALLENGES OVER THE LAST COUPLE OF
DAYS.
MARINE
(TONIGHT THROUGH NEXT WEDNESDAY)
ISSUED AT 1033 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 ARE SUBSIDING NOW THROUGH FRIDAY
BEFORE ANOTHER STRONG BREEZE REBUILDS SEAS THIS WEEKEND 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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