330
FXUS66 KMTR 150439
AFDMTR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
939 PM PDT MON APR 14 2025
..NEW AVIATION
SYNOPSIS
ISSUED AT 311 PM PDT MON APR 14 2025
A PATTERN CHANGE BEGINS ON TUESDAY BRINGING COLDER TEMPERATURES
TUESDAY INTO THURSDAY. WARM TEMPERATURES RETURN BY THE WEEKEND.
SLIGHT CHANCE FOR THUNDERSTORMS WEDNESDAY.
UPDATE
ISSUED AT 821 PM PDT MON APR 14 2025
ISOLATED THUNDERSTORMS ARE THE BIGGEST FORECAST CONCERN OVER THE
NEXT 48 HOURS OR SO. IN TERMS OF INGREDIENTS THAT ARE CRITICAL TO
THUNDERSTORM DEVELOPMENT (LIFT, INSTABILITY, AND MOISTURE), THE
UPPER-LEVEL LOW IS THE CULPRIT WITH THE 00Z OAK SOUNDING REVEALING
CONDITIONALLY UNSTABLE LAPSE RATES IN THE MID-LEVELS AND AN MU
CAPE VALUE OF 107 J/KG WITH CIN OF -137 J/KG AT 832 MB, AND A
PRECIPITABLE WATER VALUE OF 0.49 INCHES. THE CONVECTION IS
EXPECTED TO BE ELEVATED AND THE SOUNDING REVEALS THAT THE COLUMN
HAS A LOT OF WORK TO DO IN TERMS OF MOISTENING UP THE MID-LEVELS
AND PUTTING THE INSTABILITY TO WORK. OUTSIDE OF THE PRIMARY HAZARD
OF LIGHTNING, I THINK WIND WILL BE THE SECONDARY HAZARD IF AN
ELEVATED RAIN SHOWER/THUNDERSTORM WERE TO DEVELOP AS THEY WILL
LIKELY RESULT IN VIRGA AND THUS GUSTY OUTFLOWS.
SARMENT
SHORT TERM
(THIS EVENING THROUGH TUESDAY)
ISSUED AT 311 PM PDT MON APR 14 2025
AS THE RIDGE STARTS TO EXIT TO THE EAST AND MAKES WAY FOR THE UPPER
LEVEL LOW TO TAKE INFLUENCE OVER OUR AREA, TEMPERATURES WILL BEGIN
TO LOWER. OVERNIGHT TEMPERATURES WILL SEE ABOUT 2-6 DEGREES
DIFFERENCE FROM LAST NIGHT TO TONIGHT WITH TEMPERATURES IN THE MID
TO HIGH 40S. THE MAX TEMPERATURES ON TUESDAY WILL SHOW A MORE
NOTICEABLE DIFFERENCE WITH A 6-12 DEGREES DIFFERENCE INLAND.
ALONG THE COAST, TEMPERATURES WILL BE IN THE UPPER 50S TO 60S FOR
THE MOST PART, BUT INLAND AREAS WILL DROP TO WIDESPREAD 60S, WITH
HIGHER TERRAIN SEEING UP TO LOW 70S. THE MARINE LAYER WILL REBUILD
TONIGHT BRINGING ANOTHER ROUND OF FOG AND/OR DRIZZLE ALONG THE
COAST EARLY TUESDAY MORNING. THERE IS A CHANCE THAT THE FOG WILL
PUSH FURTHER INLAND NEAR NORTH BAY AND MONTEREY BAY AS WELL.
MODELS DO SHOW A SIGNAL FOR SOME INSTABILITY OVERNIGHT INTO EARLY
TUESDAY MORNING. WHILE THE PROBABILITY OF THUNDERSTORMS (AROUND 15-
20%) PEAKS LATE WEDNESDAY INTO THURSDAY, WE WILL NEED TO MONITOR
TRENDS FOR CONVECTION LATE THIS EVENING AND INTO THE PRE-DAWN HOURS
ON TUESDAY, ALTHOUGH PROBABILITY IS VERY LOW. STEEP MID-LEVEL LAPSE
RATES ON THE ORDER OF 8 C/KM ARE ANTICIPATED TO OVERSPREAD THE
REGION FROM THE SOUTH AND SOUTHEAST AND PRECIPITABLE WATER VALUES
WILL INCH ABOVE 0.75", BUT THE BULK OF THE UPPER LEVEL MOISTURE
REMAINS DISPLACED FROM THE LIFT. THEREFORE, WE WILL CONTINUE TO
MONITOR THE TRENDS FOR TONIGHT INTO TUESDAY MORNING.
LONG TERM
(TUESDAY NIGHT THROUGH NEXT SUNDAY)
ISSUED AT 311 PM PDT MON APR 14 2025
THE UPPER LEVEL LOW THAT SITS OFF THE COAST OF SOUTHERN CA CONTINUES
TO STRENGTHEN AND WILL GRADUALLY MOVE INLAND. THIS WILL ALLOW FOR A
RETURN OF PREDOMINATELY ONSHORE FLOW AND COLDER TEMPERATURES, ALONG
WITH AN INCREASE IN CLOUD COVER AND MOISTURE FROM THE SOUTH. MODELS
CONTINUE TO SHOW AGREEMENT THAT THE LOW PRESSURE SYSTEM WILL BRING
SOME UNSTABLE ATMOSPHERE OVER OUR AREA WEDNESDAY AFTERNOON AND
CONDITIONS LOOK A BIT MORE FAVORABLE FOR HIGH-BASED CONVECTION.
ALSO, SPC HAS HIGHLIGHTED OUR AREA UNDER A GENERAL RISK FOR
THUNDERSTORM. THEREFORE, WE HAVE ADDED A CHANCE (15-20%) FOR
ISOLATED THUNDERSTORMS FOR WEDNESDAY, ESPECIALLY IN THE AFTERNOON.
IN ADDITION, WITH THE DEEPENING OF THE MARINE LAYER, THERE IS A
CHANCE FOR MORNING COASTAL FOG AND DRIZZLE.
ON FRIDAY, CLUSTER ANALYSIS SHOWS A REASONABLE AGREEMENT FOR ANOTHER
RIDGE PUSHING IN FROM THE EAST PACIFIC, BRINGING BACK SOME WARMER
TEMPERATURES AND DRIER CONDITIONS FOR THE WEEKEND. SO FAR, INLAND
AREAS ARE EXPECTED TO REACH IN THE MID TO HIGH 70S, WHICH REFLECTS
CLOSE TO NORMAL AVERAGE TEMPERATURES.
AVIATION
(06Z TAFS)
ISSUED AT 936 PM PDT MON APR 14 2025
MODERATE WINDS REDUCE INTO THE NIGHT BECOMING LIGHT. LOW CLOUDS ARE
ALREADY AFFECTING THE MONTEREY BAY TERMINALS AND HAF. THESE CLOUDS
WILL SLOWLY MOVE FARTHER INLAND OVERNIGHT AFFECTING MOST OF THE TAF
SITES. ADDITIONALLY, TERMINALS ALONG THE COAST AS WELL AS STS LOOK TO
HAVE CIGS FALL TO LIFR LEVELS WITH FOG AFFECTING THOSE SITES THROUGH
A GOOD PORTION OF TUESDAY MORNING. CLOUD COVER BEGINS TO ERODE IN
THE MID TO LATE MORNING, BUT WIDESPREAD CLEARING ISN'T EXPECTED
UNTIL TUESDAY AFTERNOON AS MODERATE WINDS BUILD AND HELP MIX OUT THE
CLOUD COVER. IFR CIGS RETURN INTO TUESDAY NIGHT AS WINDS REDUCE.
VICINITY OF SFO...VFR LASTS INTO EARLY TUESDAY. WINDS ARE REDUCING,
BECOMING LIGHT AND LOOM TO TURN SLIGHTLY MORE SOUTHERLY THROUGH THE
NIGHT AND INTO THE EARLY AFTERNOON. CIGS FILL OVER THE OAK AND THE
EASTERN PORTIONS OF THE SF BAY, BUT STRUGGLE TO CONSISTENTLY FILL
OVER SFO IN THE MID MORNING, BEFORE EXITING IN THE LATE MORNING.
WEST WINDS WILL INCREASE AGAIN INTO TUESDAY AFTERNOON, BUT ONLY TO
MODERATE SPEEDS BEFORE BECOMING LIGHT AGAIN INTO THAT NIGHT.
SFO BRIDGE APPROACH...SIMILAR TO SFO
MONTEREY BAY TERMINALS...MVFR CIGS HAVE FILLED OVER THE TERMINALS.
THESE CIGS LOWER TO IFR IN THE EARLY NIGHT. FOG AND LIFR CIGS ARE
EXPECTED INTO THE LATE NIGHT AND LAST THROUGH MUCH OF THE MORNING
WITH LIGHT WINDS. VFR RETURNS INTO TUESDAY AFTERNOON AS CIGS RETREAT
INTO THE BAY AND MODERATE WIND BUILD.
MARINE
(TONIGHT THROUGH NEXT SUNDAY)
ISSUED AT 821 PM PDT MON APR 14 2025
LIGHT TO MODERATE WINDS LAST THROUGH MUCH OF THE WEEK. MODERATE
SEAS HOLD THROUGH MIDWEEK OR SO, AND THEN BUILD INTO THE LATTER
PORTION OF THE WORK WEEK. NORTHWESTERLY WINDS WILL INCREASE AS
WELL LATE IN THE WEEK LEADING TO CONCERNS FOR SMALLER CRAFT.
MTR WATCHES/WARNINGS/ADVISORIES
CA...NONE.
PZ...NONE.
SHORT TERM...SO
LONG TERM....SO
AVIATION...MURDOCK
MARINE...MURDOCK
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