987
FXUS66 KSGX 170837
AFDSGX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
137 AM PDT FRI JUL 17 2026
SYNOPSIS
NOT AS HOT WITH HIGH TEMPERATURES RETURNING TO NEAR NORMAL TODAY
INTO MUCH OF NEXT WEEK. MONSOONAL MOISTURE REMAINS IN PLACE
THROUGH NEXT WEEK FOR CONTINUED CHANCES OF SHOWERS AND
THUNDERSTORMS OVER THE MOUNTAINS AND OCCASIONALLY INTO THE DESERTS
EACH AFTERNOON AND EARLY EVENING.
DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
MID LEVEL CLOUDS FROM EARLIER CONVECTION ARE MOVING ACROSS THE
REGION THIS MORNING. BASED ON CURRENT SATELLITE TRENDS, IT DOES
NOT APPEAR THAT ENOUGH CLOUD COVER WILL BE IN PLACE TO INHIBIT
CONVECTION THIS AFTERNOON. WITH WEAK SOUTHERLY MID-LEVEL FLOW IN
PLACE, EXPECT CONVECTION TO BE FOCUSED OVER THE MOUNTAINS AND
LOCALLY INTO THE HIGH DESERT. THE 00Z KNKX SOUNDING HAD AROUND 1.5
INCH OF PRECIPITABLE WATER, WHICH IS FORECAST TO INCREASE
SLIGHTLY TODAY. SUFFICIENT PW COMBINED WITH WEAK STEERING
FLOW/NEAR STATIONARY STORMS WILL INCREASE THE RISK OF FLASH
FLOODING THIS AFTERNOON WHERE STRONGER STORMS OCCUR. SOME CAMS ARE
SHOWING HOURLY RAINFALL AMOUNTS IN EXCESS OF 1 INCH, AND 90TH
PERCENTILE 1 HOUR PRECIPITATION FROM THE REFS IS AROUND 1.25 INCH,
THOUGH VERY LOCALIZED.
FOR THE REMAINDER OF THE FORECAST AREA, LOW CLOUDS AND PATCHY FOG
ALONG THE COAST AND UP TO A FEW MILES INLAND WILL CLEAR BY LATE
MORNING. THE UPPER LEVEL HIGH CONTINUES TO WEAKEN WITH HIGH
TEMPERATURES RETURNING TO NEAR NORMAL, THOUGH CONTINUED HUMIDITY
WILL KEEP NIGHTTIME TEMPERATURES ELEVATED.
THE UPPER LEVEL PATTERN REMAINS LARGELY UNCHANGED THIS WEEKEND
THROUGH NEXT WEEK WITH BROAD UPPER LEVEL RIDGING ACROSS THE
CENTRAL US, WEAK TROUGHING OFF THE WEST COAST, AND A PAIR OF
TROPICAL SYSTEMS PASSING BY TO THE SOUTHWEST. THIS WILL MAINTAIN
SOUTHERLY OR EASTERLY FLOW ALOFT AND MONSOONAL MOISTURE ACROSS THE
REGION. MOISTURE AND INSTABILITY DECREASE SLIGHTLY THIS WEEKEND
INTO EARLY NEXT WEEK FOR LESS WIDESPREAD CONVECTION WITH LOWER
RAINFALL RATES EACH AFTERNOON. BOTH THE EC AND GFS ENSEMBLE MEANS
SHOW AN INCREASE IN PRECIPITABLE WATER TOWARDS THE MIDDLE OF NEXT
WEEK, THOUGH THE SPREAD IS SOMEWHERE ON THE ORDER OF 0.5" OR MORE,
LIKELY DUE TO DIFFERENCES IN THE PLACEMENT IN THE UPPER LEVEL
HIGH. AROUND 51% OF THE MEMBERS HAVE THE HIGH IN A MORE FAVORABLE
POSITION NEAR THE FOUR CORNERS REGION, WHILE THE REMAINING 49%
HAVE THE HIGH CENTERED CLOSER TO TEXAS, PUTTING US ON THE FRINGES
OF THE MOISTURE FOR LOWER PRECIPIATION CHANCES. OTHERWISE JUST
MINOR FLUCTUATIONS IN TEMPERATURES WITH HIGHS GENERALLY IN THE MID
TO UPPER 70S ALONG THE COAST, UPPER 80S TO 90S IN THE VALLEYS,
UPPER 70S TO LOW 90S IN THE MOUNTAINS, UPPER 90S TO LOW 100S IN
THE HIGH DESERT, AND 100-110 IN THE LOW DESERT.
AVIATION
170630Z....COAST/VALLEYS...INITIALLY PATCHY LOW CLOUDS BASED 700-
1000 FT MSL WILL CONTINUE TO SPREAD THROUGH COASTAL AREAS. IMPACTS
ARE EXPECTED AT THE MAJOR COASTAL SITES (KSAN/KCRQ/KSNA) BY 10Z, BUT
CONFIDENCE IN SPECIFIC COVERAGE IS RELATIVELY LOW AS MID-LEVEL
MONSOONAL MOISTURE/CLOUDS MOVE IN OVERNIGHT, WHICH MAY LIMIT THE
COVERAGE OF THE MARINE LAYER CLOUDS. PATCHY MINOR VIS REDUCTIONS (2-
5SM) EXPECTED ALONG ELEVATED COASTAL TERRAIN. LOW CLOUDS WILL CLEAR
TO THE COAST BY 16-17Z, WITH MORE SOUTHERLY BREEZES EXPECTED NEAR
THE COASTLINE FRIDAY AFTERNOON. LOW CLOUDS SIMILAR IN BASES AND
COVERAGE MOVE INTO SOUTH SD COASTAL AREAS AFTER 05Z SAT, MOVING
NORTH AND INLAND THROUGH ABOUT 12Z SAT.
MOUNTAINS/DESERTS
PERIODS OF HIGH CLOUDS AOA 15,000 FT AND VFR
CONDITIONS EXPECTED THROUGHOUT THE PERIOD. SCT CU BASED 10-12 KFT
AND ISO-SCT SHRA/TSRA REDEVELOP OVER THE MTNS FRIDAY AFTERNOON, MOST
LIKELY 20Z FRI THROUGH 01Z SAT. ANY STORMS THAT DEVELOP MAY PRODUCE
LIGHTNING, GUSTY WINDS, AND VIS REDUCTIONS.
MARINE
NO HAZARDOUS MARINE CONDITIONS ARE EXPECTED THROUGH MONDAY.
BEACHES
HIGH AMPLITUDE SOUTHERLY SWELL (4-6 FT WITH A PERIOD OF 12-13
SECONDS) WILL BUILD SATURDAY INTO SUNDAY, BRINGING ELEVATED SURF AND
STRONG RIP AND LONGSHORE CURRENTS FOR SUNDAY THROUGH AT LEAST
TUESDAY. HIGHEST SURF, UP TO 7-9 FT, WILL BE ALONG SOUTH AND
SOUTHWEST-FACING BEACHES.
SKYWARN
SKYWARN ACTIVATION IS NOT REQUESTED. HOWEVER WEATHER SPOTTERS ARE
ENCOURAGED TO REPORT SIGNIFICANT WEATHER CONDITIONS.
SGX WATCHES/WARNINGS/ADVISORIES
CA...NONE.
PZ...NONE.
PUBLIC...SS
AVIATION/MARINE/BEACHES...CSP
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