399
FXUS66 KSGX 170928
AFDSGX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
228 AM PDT SUN MAY 17 2026
SYNOPSIS
COOLER WEATHER PERSISTS THROUGH THE WEEKEND, WITH A DEEPER, MORE
PERSISTENT MARINE LAYER AND NIGHT AND MORNING COASTAL LOW CLOUDS
EXTENDING WELL INLAND AND ONTO THE COASTAL SLOPES OF THE
MOUNTAINS. SOUTHWEST TO WEST WINDS FOR THE MOUNTAINS AND DESERTS
WILL GUST TO 40 TO 50 MPH THROUGH SUNDAY, WITH ISOLATED GUSTS TO
65 MPH. GRADUALLY WARMER, DRY WEATHER WITH GENERALLY WEAK WINDS
WILL FOLLOW MONDAY THROUGH THURSDAY, FOLLOWED BY A SLIGHT
COOLDOWN FROM THURSDAY INTO FRIDAY.
DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
TODAY THROUGH TOMORROW NIGHT...
CURRENTLY, GOES NIGHT FOG 10.3 REVEALS THE FORMATION OF THE MARINE
LAYER TAKING SHAPE IN VICINITY OF SAN CLEMENTE WITH A WEAK COASTAL
EDDY BECOMING ESTABLISHED OVER THE INNER WATERS OF THE SOCAL BIGHT.
THIS WILL HELP TO ALLOW THE MARINE LAYER TO THICKEN UP A LITTLE BIT
MORE THROUGH THE EARLY HOURS, AND THERE COULD EVEN BE A FEW AREAS OF
DRIZZLE AS A RESULT, ESPECIALLY ALONG SOME OF THE COASTAL SLOPES AND
INLAND FOOTHILLS.
AN "INSIDE SLIDER" TYPE OF MAJOR SHORTWAVE TROUGH IS CONTINUING TO
DEEPEN AND PROPAGATE OVER THE DESERT SOUTHWEST THIS WEEKEND, WHICH
IS RESULTING IN RATHER STRONG AND GUSTY OVER THE HIGHER TERRAIN OUT
OF THE WEST TO SOUTHWEST, AND ESPECIALLY THROUGH THE MOUNTAIN
CANYONS, WHERE WINDS WILL BE SUSTAINED UP AROUND 40 TO 50 MPH BY
LATER THIS AFTERNOON FOR WIND-PRONED AREAS. THERE COULD ALSO BE SOME
ISOLATED GUSTS APPROACHING 65 TO 70 MPH FOR THE WINDIEST AREAS,
NAMELY WITHIN THE GAPS AND ALONG DESERT SLOPES ACROSS THE APPLE AND
LUCERNE VALLEYS. THERE COULD BE SOME AREAS OF BLOWING DUST, AND
ESPECIALLY WITHIN THE COACHELLA VALLEY. FOR THE HIGH DESERTS, AS MIN
RH VALUES DROP INTO THE LOW TEENS BY LATER THIS AFTERNOON WITH THE
STRONG AND GUSTY WINDS, CONDITIONS WILL BE FAVORABLE FOR FIRE GROWTH
AND SPREAD, ALTHOUGH FUELS ARE NOT YET CRITICAL FOR THESE AREAS AND
RECOVERIES OVERNIGHT WILL BE RESPECTABLE. ONSHORE FLOW WILL ALSO
CONTINUE TO BE MORE ENHANCED, LEADING TO A MORE PERSISTENT MARINE
LAYER, WHICH WILL LIKELY REMAIN RATHER PREVALENT FOR THE COASTAL
AREAS FOR TODAY, ALONG WITH COOLER TEMPERATURES STRETCHING INLAND.
HIGHS WILL BE AS MUCH AS 10 DEGREES BELOW AVERAGE FOR SOME LOCATIONS
WITHIN THE IE AND INLAND AREAS. GIVEN THE TRACK OF THIS SYSTEM, IT
SHOULD REMAIN DRY, WITH ONLY PERHAPS A FEW AREAS OF DRIZZLE WILL BE
POSSIBLE AGAINST THE COASTAL SLOPES DURING THE EARLY MORNING HOURS
TOMORROW, OTHERWISE JUST COOLER AND MORE BREEZY THROUGHOUT FOR
TODAY, FOLLOWED BY WEAKENING WINDS AND SLIGHTLY WARMER TEMPERATURES
FOR TOMORROW.
TUESDAY THROUGH SATURDAY...
AFTER PASSAGE OF THE TROUGH, HIGH PRESSURE IS GOING TO BUILD BACK IN
BEHIND IT GOING INTO TUESDAY, WITH DIMINISHING WINDS SWITCHING TO A
WEAK OFFSHORE FLOW ALOFT RETURNING THROUGH THE MIDDLE OF THE WEEK.
THIS WILL RESULT IN GRADUAL WARMING THROUGH WEDNESDAY BEFORE THE
LONGWAVE PATTERN BECOMES MORE ZONAL WITH ONLY WEAK RIDGING ALOFT
GOING INTO THE LATTER HALF OF THE WEEK. THIS WILL GIVE WAY TO THE
APPEARANCE OF THE MORE COMMON "MAY GREY" DIURNAL PATTERN BECOMING
MORE PREDOMINANT BY LATER IN THE WORK WEEK, WITH BETTER COVERAGE
ALONG THE COASTAL AREAS THROUGHOUT THE DAY, AND TEMPERATURES SLOWLY
COOLING OFF FROM THURSDAY INTO FRIDAY. TEMPERATURES WILL THEN LEVEL
OFF BY SATURDAY, AND BE RIGHT AROUND THE SEASONAL AVERAGE FOR THIS
TIME OF YEAR FOR MOST LOCATIONS. DRY CONDITIONS LOOK TO ALSO PERSIST
GOING INTO THE FOLLOWING WEEKEND AS ENSEMBLES REFLECT PWAT ANOMALIES
BEING NEARLY NEUTRAL, OR ON THE DRIER SIDE THROUGH THEN.
AVIATION
171000Z...COAST/VALLEYS...MULTIPLE SCT-OVC DECKS WITH ONE LAYER
CLOSER TO 2000-2500FT MSL AND ANOTHER 3000-4000FT MSL. MORE
WIDESPREAD MVFR CIGS THIS MORNING AFTER 12Z, FILLING IN ALONG THE
COASTLINE. LOCALIZED VIS REDUCTIONS TO 3-6SM, PRIMARILY WHERE CLOUDS
INTERSECT TERRAIN AND IN INLAND VALLEYS. CLOUDS SHOULD BEGIN TO
CLEAR OUT BY 18-20Z, ALTHOUGH SOME MAY LINGER IN INLAND VALLEYS
THROUGH THE AFTERNOON. LOW CLOUDS BASED > 2500FT MSL WILL MOVE
INLAND AGAIN AS EARLY AS 23Z, AND WILL FILL IN SUFFICIENTLY TO MUCH
OF THE INLAND EMPIRE AND SAN DIEGO COUNTY BY 06Z. BASES MAY RISE A
BIT AFTER 12Z MON.
MOUNTAINS/DESERTS...GUSTY NORTH TO NORTHWEST WINDS THIS MORNING,
INTENSIFYING AFTER 18Z WITH WIDESPREAD 30-40 KNOT SURFACE GUSTS
EXPECTED IN THE DESERTS, LOCALLY UP TO 55-60 KNOTS IN VULNERABLE
MOUNTAIN PASSES SUCH AS THE BANNING PASS. MOD UP/DOWNDRAFTS AND
LOCAL LLWS IN LEE OF MOUNTAINS AS WELL AS LOCALIZED VIS REDUCTIONS
TO 4-6SM EXPECTED, ESPECIALLY DURING PERIODS OF STRONG GUSTS. WINDS
WEAKEN AFTER 06Z MON, BUT WILL REMAIN ELEVATED IN WIND PRONE SPOTS.
MARINE
WEST-NORTHWEST GUSTS UP TO 20 KNOTS REMAIN POSSIBLE FOR THE OUTER
COASTAL WATERS NEAR SAN CLEMENTE ISLAND THROUGH 7AM THIS MORNING. IN
ADDITION TO THE WINDS, SEAS OF 7-10 FEET WITH A 9-12 SECOND PERIOD
WILL GENERATE CHOPPY SEAS. WINDS AND SEAS WILL SLOWLY DIMINISH
THROUGH THE REMAINDER OF THE DAY.
SKYWARN
SKYWARN ACTIVATION IS NOT REQUESTED. HOWEVER WEATHER SPOTTERS ARE
ENCOURAGED TO REPORT SIGNIFICANT WEATHER CONDITIONS.
SGX WATCHES/WARNINGS/ADVISORIES
CA...BEACH HAZARDS STATEMENT THROUGH MONDAY MORNING FOR ORANGE COUNTY
COASTAL AREAS-SAN DIEGO COUNTY COASTAL AREAS.
WIND ADVISORY UNTIL 11 PM PDT THIS EVENING FOR APPLE AND LUCERNE
VALLEYS-RIVERSIDE COUNTY MOUNTAINS-SAN BERNARDINO COUNTY
MOUNTAINS-SAN DIEGO COUNTY DESERTS-SAN DIEGO COUNTY
MOUNTAINS-SAN GORGONIO PASS NEAR BANNING.
PZ...SMALL CRAFT ADVISORY UNTIL 7 AM PDT THIS MORNING FOR WATERS FROM
SAN MATEO POINT TO THE MEXICAN BORDER EXTENDING 10 TO 60 NM
OUT INCLUDING SAN CLEMENTE ISLAND.
PUBLIC...STEWEY
AVIATION/MARINE...ZUBER
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