428
FXUS66 KSGX 060446
AFDSGX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
946 PM PDT SUN APR 5 2026
SYNOPSIS
PATCHY FOG MAY DEVELOP TONIGHT INTO MONDAY MORNING ALONG THE COAST,
WITH THE POTENTIAL FOR LOCALLY DENSE FOG ON THE COASTAL MESAS. LOW
CLOUDS AND FOG WILL CONTINUE MOST NIGHTS AND MORNINGS THIS WEEK, BUT
THE MARINE LAYER WILL BECOME DEEPER, LESSENING THE CHANCES FOR DENSE
FOG. TEMPERATURES WILL FLUCTUATE A FEW DEGREES EACH DAY THROUGH MID-
WEEK, BUT MOSTLY STAY ABOVE AVERAGE FOR THIS TIME OF YEAR. PATTERN
CHANGE EXPECTED FOR THE END OF NEXT WEEK, WITH COOLER, WINDIER, AND
WETTER CONDITIONS EXPECTED.
DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
EVENING UPDATE
CURRENT SATELLITE IMAGERY SHOWS WIDESPREAD HIGH CLOUDS OVER
SOUTHERN CALIFORNIA THIS EVENING WITH MORE CLOUD COVER UPSTREAM.
THIS MAY HINDER LOW CLOUD DEVELOPMENT FOR COASTAL AREAS TONIGHT
DESPITE INCREASING ONSHORE FLOW. THE LATEST MODEL GUIDANCE HAS
BACKED OFF ON BOTH THE PROBABILITY AND COVERAGE OF LOW CLOUDS. IF
LOW CLOUDS MANAGE TO DEVELOP, PATCHY FOG WILL BE POSSIBLE ALONG
ELEVATED COASTAL TERRAIN.
OTHERWISE, THE FORECAST IS STILL ON TRACK WITH INCREASING ONSHORE
FLOW EXPECTED THROUGH THE WORKWEEK AHEAD OF A WEEKEND STORM
SYSTEM. GEFS AND ECMWF ENSEMBLES CONTINUE TO DISAGREE ON TIMING
OF THE HEAVIEST PRECIP AS DESCRIBED IN THE PREVIOUS DISCUSSION.
OTHERWISE, THE ONLY NOTABLE CHANGE IS A CONTINUED TREND TOWARD
SLIGHTLY WETTER SOLUTIONS. NBM PROBABILITY OF EXCEEDING 0.5" OF
PRECIPITATION IS NOW AROUND 30-40% FOR MOST OF THE COASTAL BASIN.
PREVIOUS DISCUSSION (1215 PM SUNDAY)
PERIODS OF HIGH CLOUD COVERAGE ARE EXPECTED TO CONTINUE INTO
MONDAY. THE PRESSURE GRADIENT IS TRENDING MORE ONSHORE COMPARED TO
NOON YESTERDAY WITH THE PRESSURE GRADIENT -1.1 MB FROM SAN-DAG.
THE TREND IS EXPECTED TO CONTINUE TO SKEW MORE ONSHORE, WHICH MAY
ALLOW FOR PATCHY LOW CLOUDS AND FOG TO DEVELOP TONIGHT INTO MONDAY
MORNING. ONE POTENTIAL HICCUP TO FOG DEVELOPMENT COULD BE HOW
WIDESPREAD THE HIGH CLOUD COVERAGE IS. MORE WIDESPREAD HIGH CLOUDS
WILL LESSEN FOG CHANCES AND LESS WILL INCREASE THEM. IF FOG
DEVELOPS, IT MAY BE LOCALLY DENSE. THE MOST LIKELY PLACE FOR DENSE
FOG TO DEVELOP IS NEAR HIGHER COASTAL TERRAIN. LOW CLOUDS AND FOG
ARE EXPECTED TO REMAIN PRESENT EACH NIGHT AND MORNING FOR MUCH OF
THIS WEEK BUT A DEEPENING MARINE LAYER WILL LIMIT CHANCES FOR
COASTAL DENSE FOG.
HIGHS ON MONDAY ARE EXPECTED TO BE A FEW DEGREES COOLER ACROSS THE
AREA DUE TO A PASSING SHORTWAVE TROUGH. BREEZY WESTERLY WINDS MAY
DEVELOP OVER THE MOUNTAINS AND LOCALLY INTO THE DESERTS, BUT NO
IMPACTS EXPECTED. WEAK RIDGING WILL BUILD OVER CALIFORNIA ON
TUESDAY, WHICH WILL BRING A DEGREE OR TWO OF WARMING TO SOME INLAND
LOCATIONS. THE RIDGE WILL QUICKLY BE PUSHED ASIDE ON WEDNESDAY AS
STRONGER TROUGHING SETS UP OVER THE EASTERN PACIFIC.
THERE REMAINS QUITE A BIT OF UNCERTAINTY IN THE ENSEMBLE GUIDANCE IN
REGARDS TO THE TIMING OF THE LOW'S PASSAGE AND EXPECTED
PRECIPITATION AMOUNTS. OVERALL, TIMING OF THE ONSET OF PRECIPITATION
HAS TRENDED LATER, BUT MEMBERS OF THE GEFS ARE STILL SHOWING A
QUICKER PASSAGES OF THE LOW WITH THE BULK OF THE PRECIPITATION
CENTERED ON FRIDAY/SATURDAY, WHILE THE MAJORITY OF THE ENSEMBLE
MEMBERS OF THE ECMWF ARE SHOWING A SLOWER PROGRESSION AND THE BULK
OF THE PRECIPITATION CENTERED SATURDAY/SUNDAY. BOTH OF THE GLOBAL
MODELS HAVE QUITE A BIT OF SPREAD IN PRECIPITATION AMOUNTS AS WELL.
NBM PROBABILITIES OF 48 HOUR RAINFALL TOTALS (5 AM FRIDAY-5AM
SUNDAY) EXCEEDING 0.50" ARE HIGHEST IN THE MOUNTAINS AT 50-60
PERCENT AND AROUND 20 PERCENT FOR THE COAST AND VALLEYS. THE HIGH
DESERT HAS ABOUT A 10 PERCENT CHANCE WITH LESS THAN 5 PERCENT CHANCE
FOR THE LOW DESERT. IN ADDITION TO TIMING OF RAINFALL, THE FORWARD
PROGRESSION OF THE LOW WILL INFLUENCE WHEN THE STRONGEST WINDS AND
COLDEST CONDITIONS WILL OCCUR. SOME SNOW IS EXPECTED OUT OF THIS
SYSTEM BUT THERE STILL REMAINS CONSIDERABLE UNCERTAINTY IN SNOW
LEVELS. THE SPREAD IN SNOW LEVEL GUIDANCE FROM THE NBM RANGES FROM
7000-9000 FT ON FRIDAY AND 6500-7500 FT ON SATURDAY AND SUNDAY.
AVIATION
060415Z...GENERALLY VFR WITH BKN-OVC CLOUDS AOA 15K FT THROUGH
TONIGHT. CONFIDENCE CONTINUES TO INCREASE ON CLEARER SKIES FOR
MONDAY MORNING FOR COASTAL TAF SITES. IF ANY LOW CLOUDS 1000-1600 FT
MSL MAKE IT TO COASTAL AREAS, THIS WOULD OCCUR BETWEEN 12-17Z MON.
HIGHEST CHANCE FOR LOW CLOUDS IS ACROSS SAN DIEGO COUNTY. VIS
RESTRICTIONS 2-5 SM OVER HIGHER COASTAL TERRAIN IF CLOUDS
MATERIALIZE. HIGH CLOUDS DECREASING THROUGHOUT THE DAY ON MONDAY.
MARINE
NO HAZARDOUS MARINE CONDITIONS EXPECTED THROUGH WEDNESDAY. WINDS AND
SEAS MAY INCREASE BY THURSDAY INTO LATER IN THE WEEK DUE TO AN
INCOMING WEATHER SYSTEM WITH LOW CONFIDENCE IN FORECAST DETAILS.
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...CO/KW
AVIATION/MARINE...APR
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