557
FXUS66 KMTR 222123
AFDMTR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
223 PM PDT TUE JUL 22 2025
..NEW SHORT TERM, LONG TERM
KEY MESSAGES
UPDATED AT 215 PM PDT TUE JUL 22 2025
- A 25% CHANCE FOR LIGHT RAIN SHOWERS ACROSS THE COASTAL WATERS
- MINOR HIGH TIDE FLOODING ACROSS SAN FRANCISCO BAY THRU THURSDAY
- BELOW TO NEAR NORMAL TEMPERATURES FOR THE NEXT 2 WEEKS
SHORT TERM
ISSUED AT 215 PM PDT TUE JUL 22 2025
(THIS EVENING THROUGH WEDNESDAY)
CONVECTION FROM EARLIER THIS MORNING HAS ALL BUT DECAYED ALONG A
SMALL CORRIDOR OF ASCENT THAT STRETCHED FROM THE BAY AREA BACK TO
THE NORTHEAST INTO THE GREAT BASIN. THIS RIBBON OF LIFT DOES
APPEAR TO STILL EXIST, BUT THE OVERALL MAGNITUDE HAS WANED WITH
THE GREATEST LIFT NOW SHIFTING EAST OF THE BAY AREA/CENTRAL COAST.
THERE REMAINS A LOWER-LEVEL REFLECTION OF THIS UPPER TROUGH STILL
AND AS A RESULT, ONSHORE FLOW CONTINUES. THIS HAS TRANSLATED TO
ENHANCED BREEZES (30-35 MPH WIND GUSTS) ACROSS GAPS, CHANNELS, AND
PASSES. OVERALL, HUMIDITY LEVELS ARE ANTICIPATED TO REMAIN ABOVE
CRITICAL CONDITIONS AND THIS WILL CURTAIL THE LARGER FIRE WEATHER
THREAT. STILL, FINE FUELS DO REMAIN CURED AND IF AN IGNITION CAN
GET GOING ACROSS ONE OF THE WIND CORRIDORS, THEN SUPPRESSION
EFFORTS MAY BE HAMPERED BY RATES OF SPREAD DUE TO THE WIND. THIS
SHOULD BE VERY LOCALIZED AND NO FIRE WEATHER HEADLINES/PRODUCTS
ARE ANTICIPATED AT THIS TIME.
HEADING INTO TONIGHT, THOUGH JUST HOW FAR THE MARINE LAYER
INVADES IS A LITTLE LESS CERTAIN. SYNOPTICALLY, BROAD 500MB
TROUGHING WILL MORPH INTO A DIFFUSE UPPER LOW THAT SHOULD PINWHEEL
SOMEWHERE NEAR THE FARALLONES. THIS WILL ENCOURAGE A LITTLE MORE
IN THE WAY OF SOUTHWESTERLY TO SOUTHERLY FLOW, EVEN DOWN TO THE
925-850MB LAYER. THE SFO-SAC MSLP DIFFERENCE OR "GRADIENT" IS
ANTICIPATED TO BE SLIGHTLY WEAKER COMPARED TO YESTERDAY AND THIS
MAY LIMIT EITHER THE DURATION AND/OR EXTENT OF STRATUS INTRUSION.
STILL THE THEME OF "NO SKY JULY" ACROSS THE IMMEDIATE COAST LINE
HOLDS TRUE AND THERE MAY NOT BE MUCH OF A CHANGE WITH REGARD TO
WEDNESDAY'S MAXT. FOR AREAS FARTHER INLAND, HOWEVER, LESS IN THE
WAY OF CLOUD COVER COULD MEAN SLIGHTLY WARMER CONDITIONS (AROUND
2-4F) ACROSS THE INTERIOR COMPARED TO TODAY, BUT IMPACTFUL HEAT IS
NOT ANTICIPATED AT THIS TIME.
SOUTHERLY TO SOUTHWESTERLY FLOW WILL ALSO ENCOURAGE DRIZZLE ALONG
THE PACIFIC COAST THROUGH ABOUT THE ENTIRETY OF THE BAY AREA AND
CENTRAL COAST. WITH THE MARINE LAYER DEPTH ESTIMATED TO BE AROUND
3,000 FEET, IT WOULDN'T BE SURPRISING TO SEE A FEW ADDITIONAL
REPORTS OF A FEW HUNDREDTHS OF AN INCH OF LIQUID IN AREA GAUGES,
ESPECIALLY ACROSS SOME OF THE FAVORED OROGRAPHIC ASCENT REGIONS
(BIG SUR COAST, SANTA CRUZ MOUNTAINS, EAST BAY HILLS, SONOMA
COASTAL RANGE). SHOWERS ARE ANTICIPATED TO REMAIN LARGELY OFFSHORE
(MAYBE A FEW ECHOES WILL DRIFT INTO COASTAL AREAS) WHERE THERE'S
A NARROW RIBBON OF HIGHER INSTABILITY (THETA-E) AIR THAT WRAPS
AROUND THE MAIN UPPER LOW. CAPE VALUES ARE UNDERWHELMING WITH
VALUES IN THE SINGLE DIGITS TO LOW TEENS AND I DON'T ANTICIPATE
WIDESPREAD RAINFALL. THAT SAID, THE RADAR SCOPE MAY BE ILLUMINATED
AND FOR THE MORNING COMMUTE, INDIVIDUALS MAY NEED TO USE THEIR
WINDSHIELD WIPERS (OR TAKE A JACKET IF COMMUTING VIA BIKE OR ON
FOOT) DUE TO DRIZZLE, SPRINKLES, OR VERY LIGHT RAIN.
LONG TERM
ISSUED AT 215 PM PDT TUE JUL 22 2025
(WEDNESDAY NIGHT THROUGH NEXT MONDAY)
THE OVERALL THEME OF COOLER TO NEAR NORMAL TEMPERATURES AND COASTAL
CLOUDINESS/DRIZZLE WILL CONTINUE THROUGH THE EXTENDED PORTION OF
THE FORECAST. CONFIDENCE IS HIGH THAT THE OVERALL SYNOPTIC REGIME
WILL REMAIN LARGELY UNCHANGED. SOME OF THE OUTLIER SOLUTIONS DO
INDICATE THAT PERHAPS THE FOUR CORNERS MID-LEVEL HIGH PRESSURE
WILL ATTEMPT TO JOG WESTWARD, BUT ONLY FOR A BRIEF AMOUNT OF TIME.
IF THIS TRANSPIRES, THEN HIGH TEMPERATURES MAY HAVE AN
OPPORTUNITY TO CLIMB ABOVE NORMAL. AT THIS TIME, HOWEVER, THAT
SUITE OF GUIDANCE THAT ADVERTISES SUCH A SOLUTION IS IN THE
MINORITY.
BROAD TROUGHING REMAINING PARKED TO THE WEST IS THE MOST
REASONABLE OUTCOME IN THE EXTENDED. AS A RESULT, ONSHORE FLOW IS
ANTICIPATED TO PERSIST, KEEPING THE HEATRISK AND THREAT OF
EXCESSIVE HEAT WELL BELOW ANY THRESHOLD NEEDED TO TRIGGER ANY
CONCERN. IN FACT, HEATRISK OUTPUT ADVERTISES ONLY MINOR TO NEAR
ESSENTIALLY ZERO THREAT FOR HEAT IMPACTING THE GENERAL POPULATION.
LONGER RANGE ENSEMBLE FORECASTS, ALBEIT THE MEANS, CONTINUE TO
INDICATE THAT THE LARGER SCALE PATTERN WILL BE DOMINATED BY WEST
COAST TROUGHING. AS SUCH, CONFIDENCE IS MEDIUM THAT THE REMAINDER
OF THE MONTH WILL LIKELY END UP BELOW NORMAL HIGH TEMPERATURE WISE
FOR MANY LOCATIONS ACROSS THE BAY AREA AND CENTRAL COAST.
AVIATION
(12Z TAFS)
ISSUED AT 422 AM PDT TUE JUL 22 2025
CURRENTLY A MIXED BAG OF LIFR-VFR AT THE TERMINALS. A SURFACE TROUGH
AND ITS ASSOCIATED HIGH CLOUDS IS ADDING SOME COMPLEXITY TO THE
FORECAST WITH STS YET TO DETERIORATE TO SUB-VFR, ALTHOUGH LOW
STRATUS CLOUDS ARE QUICKLY ENCROACHING (WITHIN 5 MILES OF) THE
TERMINAL. THAT BEING SAID, CONFIDENCE IS ONLY MODERATE ON ALL
TERMINALS (WITH THE EXCEPTION OF HAF) IMPROVING TO VFR BY THIS
AFTERNOON.
VICINITY OF SFO...CURRENTLY IFR WITH WESTERLY FLOW. WESTERLY FLOW
WILL PREVAIL THROUGH THE TAF PERIOD. WHILE IT IS LIKELY THAT
CEILINGS WILL IMPROVE TO VFR, THERE REMAINS A LOW PROBABILITY (10%
CHANCE) THAT SUB-VFR CEILINGS LINGER THROUGH THE TAF PERIOD.
SFO BRIDGE APPROACH...LOW STRATUS CLOUDS WILL LIKELY LINGER TO SOME
EXTENT WITHIN THE SAN FRANCISCO BAY.
MONTEREY BAY TERMINALS...CURRENTLY IFR WITH SOUTHWESTERLY FLOW AT
MRY AND IFR WITH NORTHWESTERLY FLOW AT SNS. HIGH CONFIDENCE IN
CEILINGS IMPROVING TO VFR BY THIS AFTERNOON; HOWEVER, THERE REMAINS
A LOW PROBABILITY (10%) THAT SUB-VFR CEILINGS LINGER THROUGH THE TAF
PERIOD, ESPECIALLY AT MRY. WESTERLY WINDS WILL PREVAIL THROUGH THE
TAF PERIOD.
MARINE
(TODAY THROUGH SUNDAY)
ISSUED AT 831 AM PDT TUE JUL 22 2025
A GENTLE TO MODERATE NORTHWESTERLY BREEZE AND GENERALLY LOW SEAS
CONTINUE THROUGH THIS WEEK. LOW CLOUDS WITH THE POSSIBILITY OF
DRIZZLE ACROSS THE WATERS THROUGH MID-WEEK.
MTR WATCHES/WARNINGS/ADVISORIES
CA...COASTAL FLOOD ADVISORY FROM 8 PM THIS EVENING TO 1 AM PDT
WEDNESDAY FOR CAZ006-506-508.
PZ...NONE.
SHORT TERM...BAIN
LONG TERM....BAIN
AVIATION...BEHRINGER
MARINE...BEHRINGER
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