586
FXUS66 KMTR 210446
AFDMTR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
946 PM PDT MON JUL 20 2026
..NEW AVIATION
KEY MESSAGES
UPDATED AT 154 PM PDT SUN JUL 19 2026
- APPROXIMATELY 15% CHANCE OF HIGH BASED SHOWERS THROUGH TUESDAY.
- BREEZY ONSHORE WINDS RETURN FOR THE SECOND HALF OF THE WEEK.
- TEMPERATURES WILL HOVER AROUND NORMAL THROUGH THE WEEK.
SHORT TERM
ISSUED AT 154 PM PDT MON JUL 20 2026 (THIS EVENING THROUGH
TUESDAY NIGHT)
AFTERNOON SATELLITE AND RADAR SHOW CLOUDS AND SHOWERS STREAMING
OVER THE AREA FROM POST TROPICAL STORM ELIDA. THE SHOWERS ARE
HIGH BASED, MEANING THE BOTTOMS OF THE THE SHOWERS ARE AROUND
5-8000 FEET. AT THIS ELEVATION IN SUMMER MONTHS, THE RAIN COMING
OUT OF THE SHOWERS TYPICALLY EVAPORATED BEFORE HITTING THE GROUND.
EVEN SO, WITH THE FORECAST CYCLE, SHOWERS WERE ADDED INTO MUCH OF
THE AREA WITH QPF LIMITED TO 0.01", WHICH IS GENEROUS. REALLY
SHOWERS WILL BE LUCKY TO REACH A TRACE.
THE OVERALL PATTERN IS FAIRLY INTERESTING WITH A BROAD RIDGE OVER
THE WESTERN US, TRYING TO FLEX INTO THE WEST COAST, BUT CHALLENGED
BY TROUGH OVER THE EASTERN PACIFIC. THIS TROUGH IS THE EXIT ROUTE
FOR POST TROPICAL STORM ELIDA, RIDING UP AND OVER THE EDGE OF THE
RIDGE. THIS IS WHERE THE COMPLEXITIES CREEP IN. THE STRENGTH OF
THE RIDGE AND TROUGH ARE NOT STATIC AND MODELS ARE TRYING TO
PROJECT THEM, BUT ONLY OFFER ABOUT A 80% VISION RATE. MEANING,
THERE IS STILL ERROR IN THE FORECAST. THE ERROR IS SHOWING UP IN
THE POP AND QPF FIELDS AND TRYING TO PLAY WITH TEMPS AS WELL. AS
STATED, THE POP FORECAST HAS FROM NBM AND OTHER MODEL GUIDANCE FOR
THE NEXT 36 HOURS AS ELIDA PASSES BY. QPF WILL REMAIN LOW, UNLESS
THERE IS A WOBBLE EASTWARD OF THE REMNANT SYSTEM. MODELS ARE
SHOWING NICE VORTICITY BANDS (AT 500, 700, AND 850 MB) SPINNING
OFF THE REMNANT LOW, HEADING OUR WAY ON WEDNESDAY. THIS COMES INTO
PLAY AS IT COULD PROVIDE A FOCUS POINT FOR MORE INTENSE SHOWERS,
IF THERE REMAINS ENOUGH MOISTURE IN THE AREA AT THAT TIME, AND
RIGHT NOW THAT DOES NOT LOOK PROBABLE. THIS WILL BE SOMETHING TO
WATCH AS THIS SYSTEM CAN STILL MAKE A WOBBLE. AT THIS TIME THERE
IS NO EXPECTATION OF DRY THUNDERSTORMS OR EVEN LIGHTNING. THE
DEPTH OF ANY CONVECTION JUST DOESN'T LOOK DEEP ENOUGH TO REACH THE
HAIL GROWTH ZONE NEEDED TO EXCHANGE CHARGES AND GENERATE
LIGHTNING. THERE WOULD NEED TO BE A SUBSTANTIAL SHIFT IN THE
PATTERN TO FIND BETTER AREAS OF INSTABILITY AND EVEN THEN, THE
SYSTEM WOULD NEED TO INTENSIFY AS UNDERGOES EXTRATROPICAL
TRANSITION, WHICH IT IS SHOWING NO SIGNS OF. NO MENTION OF DRY
THUNDERSTORMS IN THE FORECAST.
MODELS CONTINUE TO SHOW TUESDAY AS THE WARMEST DAY OF THE WEEK
WITH TEMPS RUNNING ABOUT 5ISH DEGREES ABOVE NORMAL. HOWEVER, THE
REMNANT LOW MAY PROVIDE MORE CLOUDS THAN EXPECTED AND CAP
TEMPERATURES TO AROUND NORMAL. CONFIDENCE IS HIGH THAT IN THE WAKE
OF THE REMNANT LOW TEMPS WILL COOL SLIGHTLY, AROUND 5ISH DEGREES
BELOW NORMAL. BY THE WEEKEND THE FOUR CORNERS HIGH WILL TRY TO
PRESS INTO THE AREA AGAIN CAUSING MORE WARMING.
SUMMARY: POST TROPICAL STORM OR REMNANT LOW ELIDA WILL CONTINUE TO
MAKE THE FORECAST CHALLENGING WITH RESPECT TO NEARLY ALL SENSIBLE
WEATHER ELEMENTS. KEEP AN EYE ON AN EVER CHANGING FORECAST.
LONG TERM
ISSUED AT 154 PM PDT MON JUL 20 2026 (WEDNESDAY THROUGH NEXT
SUNDAY)
IN THE WAKE OF THE REMNANT LOW CONFIDENCE IS HIGH THAT TEMPS WILL
COOL SLIGHTLY, AROUND 5ISH DEGREES BELOW NORMAL, AS TROUGHING
PREVAILS. BY THE WEEKEND THE FOUR CORNERS HIGH WILL TRY TO PRESS
INTO THE AREA AGAIN CAUSING MORE WARMING. THIS WILL TAKE US FROM A
DEEPER MARINE LAYER FOR THE SECOND HALF OF THE WORKWEEK TO A MORE
COMPRESSED ONE FOR THE WEEKEND. THE ONE THING TO WATCH FOR AS THE
TROUGH MAKES IT SELF KNOWN IS ONSHORE WINDS. WINDS FROM THE OCEAN
ON TO LAND WILL INCREASE EACH AFTERNOON. SOME KEY LOCATIONS LIKE
PETALUMA GAP, ALTAMONT, AND THROUGH THE GOLDEN GATE WILL GUST EACH
AFTERNOON. STRENGTH WILL DEPEND ON WHERE YOU ARE AT.
AVIATION
(06Z TAFS)
ISSUED AT 923 PM PDT MON JUL 20 2026
MID TO HIGH LEVEL CLOUDS ARE INTERRUPTING NORMAL RADIATIVE PROCESS
FOR WIDES SPREAD STRATUS. LOW CONFIDENCE THAT STRATUS MAY DEVELOP
DURING THE OVERNIGHT THROUGH SUNRISE TUESDAY MORNING. EXPECTING
MAINLY VFR THROUGH THE TAF PERIOD FOR MAJORITY OF THE TERMINALS
WITH THE EXCEPTION OF KHAF WHICH IS ON THE COASTLINE. BE AWARE OF
THE POTENTIAL FOR ELEVATED SHOWERS TO PRODUCE LOCALLY GUSTY AND
ERRATIC WINDS IN THEIR VICINITY THROUGH THE FORECAST PERIOD.
VICINITY OF SFO...VFR EXPECTED TO PREVAIL THROUGH THE TAF PERIOD
WITH A SLIGHT CHANCE OF IFR CEILINGS DEVELOPING LATE IN THE
OVERNIGHT THROUGH SUNRISE TUESDAY. BE AWARE OF THE POTENTIAL FOR
ELEVATED SHOWERS TO PRODUCE LOCALLY GUSTY AND ERRATIC WINDS IN
THEIR VICINITY THROUGH THE FORECAST PERIOD.
SFO BRIDGE APPROACH...SIMILAR TO SFO.
MONTEREY BAY TERMINALS...VFR IS EXPECTED TO PREVAIL WITH A SLIGHT
CHANCE OF IFR CEILINGS DEVELOPING OVERNIGHT BEFORE SUNRISE OR
SHORTLY AFTER. IF CEILINGS DON'T DEVELOP, EXPECT VFR THROUGH THE
REMAINDER OF THE FORECAST PERIOD. BE AWARE OF THE POTENTIAL FOR
ELEVATED SHOWERS TO PRODUCE LOCALLY GUSTY AND ERRATIC WINDS IN
THEIR VICINITY THROUGH THE FORECAST PERIOD.
MARINE
(TODAY THROUGH SATURDAY)
ISSUED AT 1049 AM PDT MON JUL 20 2026
LIGHT TO LOCALLY MODERATE NORTHWESTERLY WINDS WILL PREVAIL
THROUGH MIDWEEK, BECOMING MODERATE THURSDAY INTO FRIDAY. SLIGHT
TO MODERATE SEAS WILL PREVAIL. TROPICAL CYCLONE ACTIVITY IN THE
EASTERN PACIFIC OCEAN WILL SPUR SEVERAL ROUNDS OF MODERATE PERIOD
SOUTHERLY SWELLS; HAZARDOUS CONDITIONS FROM MIXED SEAS MAY RESULT.
INSTABILITY FROM THE REMNANTS OF THE TROPICAL CYCLONE WILL ALSO
BRING A SLIGHT CHANCE OF CONVECTION THAT MAY BRING SHOWERS AS WELL
AS GUSTY AND ERRATIC OUTFLOW WINDS THAT WOULD BE RESULT IN
HAZARDOUS CONDITIONS TO SMALL CRAFT.
FIRE WEATHER
ISSUED AT 154 PM PDT MON JUL 19 2026
NO SIGNIFICANT IMPACTS EXPECTED AS SUB-TROPICAL MOISTURE MOVES
OVER THE BAY AREA AND CENTRAL COAST. THERE HAS BEEN SOME
DISCUSSION OF DRY THUNDERSTORMS, BUT AS OF THIS AFTERNOON MODELS
ARE NOT INDICATING AN ENVIRONMENT THAT WOULD SUPPORT THEIR
DEVELOPMENT. AT THIS POINT I WOULD GIVE DRY THUNDERSTORMS A
PROBABILITY OF LESS THAN 1% THIS WEEK. WHAT SHOULD BE EXPECTED IS
AN ISOLATED SHOWER HERE OR THERE WITH LITTLE TO NO ACCUMULATION.
THE MARINE LAYER WILL REMAIN FAIRLY WELL MIXED OUT THROUGH TUESDAY
AFTERNOON, BUT SHOULD START TO BUILD BACK IN LATE TUESDAY AND
TUESDAY NIGHT. EXPECT IT TO REACH AROUND 1000 FEET BY MIDWEEK.
STRONG ONSHORE WINDS WILL DEVELOP EACH AFTERNOON FOR THE SECOND
HALF OF THE WEEK. THEY TYPICAL PLACES WILL GUSTS LIKE THEY DO
EVERY SUMMER AFTERNOON.
MTR WATCHES/WARNINGS/ADVISORIES
CA...NONE.
PZ...NONE.
SHORT TERM...BFG
LONG TERM....BFG
AVIATION...JM
MARINE...JM
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