061
FXUS66 KSGX 150957
AFDSGX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
257 AM PDT SUN MAR 15 2026
SYNOPSIS
MARINE LAYER LOW CLOUDS OVER THE COASTAL AREAS THIS MORNING WILL
BECOME PATCHIER WITH LESS INLAND EXTENT TONIGHT INTO MONDAY
MORNING. A WARMING TREND BEGINS TODAY WITH UNSEASONABLY HOT
WEATHER THROUGH THE WEEK. TEMPERATURES PEAK THURSDAY AND FRIDAY
WHEN HIGHS WILL BE AS MUCH AS 30 DEGREES ABOVE NORMAL. BOTH DAILY
AND MONTHLY HIGH TEMPERATURE RECORDS ARE LIKELY TO BE BROKEN THIS
WEEK.
DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
MARINE LAYER LOW CLOUDS HAVE SPREAD INTO THE WESTERN VALLEYS THIS
MORNING WITH MOSTLY CLEAR SKIES ELSEWHERE. LOW CLOUDS WILL CLEAR
TOWARDS THE COAST BY LATE MORNING AS OFFSHORE FLOW DEVELOPS.
THE HREF HAS A 60% CHANCE OF LOW CLOUDS AND FOG RETURNING TO THE
COASTAL AREAS TONIGHT INTO MONDAY MORNING, WITH LESSER INLAND
EXTENT AS THE MARINE LAYER BECOMES MORE SHALLOW. SURFACE PRESSURE
GRADIENTS REMAIN WEAKLY ONSHORE TO THE LOCAL DESERTS AS OF 2 AM,
BUT ARE FORECAST TO TRANSITION OFFSHORE LATER THIS MORNING AS
SURFACE HIGH PRESSURE BUILDS OVER THE GREAT BASIN. THIS WILL
PRODUCE LOCALLY BREEZY WINDS BELOW THE PASSES AND ON THE COASTAL
MOUNTAIN SLOPES WITH GUSTS TO AROUND 25-35 MPH. NORTHEAST TO EAST
WINDS CONTINUE INTO MONDAY, STRENGTHENING SLIGHTLY MONDAY MORNING
WHEN PEAK GUSTS WILL BE CLOSER TO 40 MPH.
A LARGE UPPER LEVEL RIDGE OF HIGH PRESSURE AMPLIFIES OFF THE WEST
COAST AND MOVES SLIGHTLY EASTWARD TODAY AND MONDAY. THIS BUILDING
RIDGE COMBINED WITH THE OFFSHORE FLOW WILL BEGIN THE WARMING
TREND, ESPECIALLY FOR AREAS WEST OF THE MOUNTAINS. TODAY, HIGHS
WILL BE AS MUCH AS 15-20 DEGREES ABOVE NORMAL IN THE VALLEYS
(80-95 DEGREES), AND AROUND 10-15 DEGREES ABOVE NORMAL ELSEWHERE.
FOR MONDAY, HIGHS WILL INCREASE TO AROUND 15-25 DEGREES ABOVE
NORMAL, WITH THE GREATEST DEPARTURE WEST OF THE MOUNTAINS WHERE
HIGHS WILL BE IN THE LOW 80S ALONG THE COAST, AND MID 80S TO MID
90S ACROSS THE INLAND COASTAL AREAS AND VALLEYS. HIGH TEMPERATURES
IN THE LOW DESERT WILL APPROACH 100 DEGREES. A HEAT ADVISORY
BEGINS FOR THE COASTAL AREAS AND VALLEYS MONDAY MORNING.
THE UPPER LEVEL HIGH SLOWLY SHIFTS EASTWARD THROUGH THE WEEK,
BECOMING CENTERED OVER CA TUE AND WED AS IT CONTINUES TO
STRENGTHEN. ENSEMBLES ARE IN GOOD AGREEMENT THROUGH THIS PERIOD,
WITH HIGH CONFIDENCE OF THE WARMING TREND CONTINUING AND HIGH
TEMPERATURES UPWARDS OF 20-25 DEGREES ABOVE NORMAL. THE UPPER HIGH
THEN SHIFTS FURTHER EAST TOWARDS THE LOWER COLORADO RIVER VALLEY
THURSDAY AND FRIDAY, PEAKING IN STRENGTH. THERE ARE STILL SOME
DISCREPANCIES IN HOW STRONG THE HIGH WILL GET. ON THE EXTREME END
OF THE FORECAST (NBM 90TH PERCENTILE), HIGH TEMPERATURES COULD
EXCEED 105 DEGREES IN THE INLAND EMPIRE AND 110 IN THE COACHELLA
VALLEY ON THURSDAY, AND CLOSE TO 110 IN THE INLAND EMPIRE AND 115
IN THE COACHELLA VALLEY ON FRIDAY. CURRENT FORECAST IS AROUND THE
NBM 50TH PERCENTILE, WHICH EXCEEDS THE EC MOS 90TH PERCENTILE BY A
FEW DEGREES. GIVEN THE LIKELIHOOD OF TEMPERATURES AROUND 30
DEGREES ABOVE NORMAL AND MODERATE TO HIGH HEATRISK, AN EXTREME
HEAT WATCH WAS ISSUED FOR THE MOUNTAINS BELOW 5500 FT AND THE LOW
DESERTS FOR THURSDAY AND FRIDAY. THE RIDGE FINALLY BEGINS TO BREAK
DOWN SATURDAY AND SUNDAY, ALLOWING FOR GRADUAL COOLING.
AVIATION
151200Z...COASTS/WESTERN VALLEYS...LARGELY UNIFORM LOW CLOUDS (BASED
800-1100FT MSL) HAVE FILLED IN THROUGH 15 MILES IN ACROSS COASTAL
SAN DIEGO COUNTY, BUT REMAIN SOMEWHAT PATCHY ACROSS ORANGE COUNTY.
THE CLOUD BASES MAY SINK A FEW HUNDRED FEET AFTER 12-15Z AS THE
COASTAL EDDY WEAKENS, WHICH COULD BRING VIS REDUCTIONS DOWN TO 4-6
SM, LARGELY ACROSS COASTAL MESAS AND INLAND VALLEYS. CIGS EXPECTED
TO SCATTER FOR THE COASTAL TAF SITES BY 17-18Z THIS MORNING, WITH
CLOUDS RETREATING OFFSHORE FOR THE AFTERNOON. PATCHIER LOW CLOUDS
CLOSER TO 400-800FT MSL LOOK TO SPREAD BACK ASHORE AFTER 06Z MONDAY,
SPREADING UP TO 10-15 MILES INLAND.
PATCHIER LOW CLOUDS 400-800 FT MSL DEVELOP AND MOVE INLAND AFTER 06Z
MON.
INLAND VALLEYS/MOUNTAINS/DESERTS... BREEZY OFFSHORE WINDS DEVELOP
THIS AFTERNOON AFTER 18Z ON THE COASTAL MOUNTAIN SLOPES, THROUGH
MOUNTAIN PASSES, AND LOCALLY STRETCHING INTO EASTERN VALLEYS. NORTH
TO NORTHEAST WIND GUSTS OF 20-25 KTS EXPECTED, LOCALLY UP
TO 35 KTS IN MOUNTAIN PASSES. GUSTS WEAKEN AFTER 03Z MONDAY.
MARINE
NO HAZARDOUS MARINE CONDITIONS ARE EXPECTED THROUGH THURSDAY.
BEACHES
A LONG PERIOD (17-19 SECOND) SOUTH-SOUTHWESTERLY SWELL (190-200
DEGREES) BUILDS TO 2-4 FEET MONDAY AFTERNOON INTO TUESDAY. BREAKING
WAVES OF 4-6 FEET ARE EXPECTED, WITH SETS UP TO 7 FEET POSSIBLE ON
SOUTH-FACING BEACHES. THIS SWELL IS EXPECTED TO PERSIST INTO
WEDNESDAY, WANING WEDNESDAY NIGHT.
SKYWARN
SKYWARN ACTIVATION IS NOT REQUESTED. HOWEVER WEATHER SPOTTERS ARE
ENCOURAGED TO REPORT SIGNIFICANT WEATHER CONDITIONS.
SGX WATCHES/WARNINGS/ADVISORIES
CA...HEAT ADVISORY FROM 10 AM MONDAY TO 8 PM PDT FRIDAY FOR ORANGE
COUNTY COASTAL AREAS-ORANGE COUNTY INLAND AREAS-SAN
BERNARDINO AND RIVERSIDE COUNTY VALLEYS-THE INLAND EMPIRE-
SAN DIEGO COUNTY COASTAL AREAS-SAN DIEGO COUNTY VALLEYS-
SANTA ANA MOUNTAINS AND FOOTHILLS.
EXTREME HEAT WATCH FROM THURSDAY MORNING THROUGH FRIDAY EVENING
FOR COACHELLA VALLEY-RIVERSIDE COUNTY MOUNTAINS-SAN
BERNARDINO COUNTY MOUNTAINS-SAN DIEGO COUNTY DESERTS-SAN
DIEGO COUNTY MOUNTAINS-SAN GORGONIO PASS NEAR BANNING.
PZ...NONE.
PUBLIC...SS
AVIATION/MARINE/BEACHES...MUNYAN
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page