029
FXUS66 KSGX 262121
AFDSGX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
221 PM PDT SAT APR 26 2025
SYNOPSIS
COOL AND CLOUDY WEATHER IS EXPECTED THROUGH TODAY, WITH LIGHT
SHOWERS AND MOUNTAIN SNOW. THERE WILL ALSO BE STRONG SOUTHWEST TO
WEST WINDS, STRONGEST THROUGH MOUNTAIN PASSES INTO DESERTS,
THROUGH LATE THIS EVENING. THERE IS A SLIGHT CHANCE OF
THUNDERSTORMS THIS AFTERNOON AND EVENING. FAIR AND WARMER WEATHER
WILL FOLLOW MOST OF NEXT WEEK, WITH THE USUAL COASTAL CLOUDS
DURING THE NIGHTS AND MORNINGS. TEMPERATUES WILL THEN COOL OFF
AGAIN LATE NEXT WEEK INTO THE WEEKEND.
DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
SHORT TERM
A LOW PRESSURE SYSTEM ALOFT IS CURRENTLY JUST WEST OF POINT
CONCEPTION, AND IS DRIVING A COLD FRONT WEST THROUGH THE AREA,
BRINGING LIGHT RAIN SHOWERS, MOUNTAIN SNOW, POSSIBLE AFTERNOON
THUNDERSTORMS, AND GUSTY SOUTHWEST TO WEST WINDS.
RAIN TOTALS FOR THIS EVENT (OR LIQUID EQUIVALENT ABOVE THE SNOW
LINE) WILL BE FROM ABOUT 0.05" TO A THIRD OF AN INCH FOR COASTAL
AND VALLEY AREAS, A COUPLE OF HUNDREDTHS TO ABOUT A TENTH OF A
INCH FOR THE WESTERN HIGH DESERT, AND 0.25" TO 0.75" FOR MOST
AREAS IN THE MOUNTAINS WITH UP TO AN INCH LOCALLY ON THE WINDWARD
SLOPES OF THE SAN BERNARDINO AND SAN GABRIEL MOUNTAINS, MOST OF
WHICH WILL FALL AS SNOW. SNOW LEVELS WITH THE FRONTAL
PRECIPITATION BAND CURRENTLY MAKING ITS WAY THROUGH THE REGION
THIS AFTERNOON ARE GENERALLY BE BETWEEN 5000 AND 6000 FEET, BEFORE
DROPPING TO 4500 TO 5000 FEET THIS EVENING AS SHOWERS BECOME
ISOLATED. WET, HEAVY SNOW TOTALS OF UP TO 5 INCHES IN THE SAN
BERNARDINO MOUNTAINS, UP TO 3 INCHES IN THE RIVERSIDE MOUNTAINS,
AND UP TO AN INCH OR SO IN THE SAN DIEGO MOUNTAINS IS EXPECTED
BETWEEN NOW AND SUNDAY AFTERNOON ABOVE 5500 FEET.
THE COACHELLA VALLEY AND SAN DIEGO DESERTS, MEANWHILE, WILL
CONTINUE TO LARGELY MISS OUT ON ANY PRECIPITATION, BUT WILL
CONTINUE TO SEE GUSTY WINDS THROUGH THIS EVENING. SOUTHWEST TO
WEST WINDS ARE 25 TO 40 MPH OVER THE MOUNTAINS AND DESERTS, WITH
GUSTS TO 55 MPH. AS PER USUAL, STRONGEST WINDS ARE THROUGH AREAS
LIKE THE BANNING/SAN GORGONIO PASS ON I-10 AND THROUGH WALKER
CANYON ON I-8, LEADING TO DIFFICULT DRIVING CONDITIONS, ESPECIALLY
FOR HIGH PROFILE VEHICLES.
THE MAIN LOW PRESSURE SYSTEM ALONG WITH THE FRONT PASS TO THE
NORTHEAST THIS EVENING, BRINGING AN END TO WIDESPREAD
PRECIPITATION BUT WITH LINGERING SHOWERS OVERNIGHT. SHOWERS TAPER
OFF FROM THE NORTHWEST TO SOUTHEAST OVERNIGHT, LINGERING IN SAN
DIEGO COUNTY LONGEST THROUGH SUNDAY MORNING. WEAKER LOW PRESSURE
REMAINS ALOFT INTO EARLY NEXT WEEK, AND LINGERING MOISTURE AND
WEAK LIFT COULD RESULT IN A FEW POP UP SHOWERS OVER THE MOUNTAINS
LATE SUNDAY AFTERNOON, BUT WITH THE MOISTURE SOURCE EFFECTIVELY
CUT OFF THE REMAINDER OF THE REGION WILL SEE DRY WEATHER. THIS
WILL RESULT IN CONTINUED COOLER THAN AVERAGE TEMPERATURES REGION-
WIDE THROUGH MONDAY, HOWEVER, ALBEIT SLIGHTLY WARMER THAN TODAY
WILL BE.
LONG TERM...TUESDAY APR 29 THROUGH SATURDAY MAY 03
WEAK HIGH PRESSURE BUILDS IN ALOFT TUESDAY AND PART OF WEDNESDAY,
BRINGING NOTICEABLY WARMER (NEAR-AVERAGE) TEMPERATURES, DRY
WEATHER, AND AVERAGE AFTERNOON BREEZES. THIS WILL ALSO MAKE THE
NIGHTLY MARINE LAYER LOW CLOUDS SHALLOWER AND MORE CONFINED TO
COASTAL AREAS. WHILE SOME DIVERGENCE IN ENSEMBLE MODEL SOLUTIONS
EXISTS THURSDAY ONWARDS, THE FLOW LOOKS TO SPLIT THURSDAY, WITH
HIGH PRESSURE OVER THE NORTHWEST U.S. AND LOW PRESSURE ALOFT OVER
SOUTHERN CALIFORNIA. THIS WON'T HAVE MUCH EFFECT BESIDES A SLIGHT
COOLING ALONG THE COAST THURSDAY THAT WILL START TO SPREAD INLAND
FRIDAY AND SATURDAY AS LARGER SCALE TROUGHING SETTLES INTO THE
WESTERN U.S. NEAR AVERAGE TEMPERATURES REGION-WIDE WILL DIP
SLIGHTLY BELOW AVERAGE FOR AREAS WEST OF THE MOUNTAINS FRIDAY,
THEN BELOW AVERAGE TEMPERATURES ARE LIKELY REGION-WIDE SATURDAY.
THE MARINE LAYER WILL DEEPEN AND SPREAD FARTHER INLAND EACH NIGHT
AND MORNING FOR THE LATTER HALF OF THE WEEK.
DEEPER LOW PRESSURE LOOKS LIKELY TO MOVE IN SUN-MON. CURRENTLY A
FAIR NUMBER OF THE MEMBERS OF BOTH THE GEFS AND ECMWF ENSEMBLE ARE
SHOWING LIGHT RAIN FOR AROUND SUNDAY AND EARLY THE NEXT WEEK, BUT
CONFIDENCE THIS FAR IN ADVANCE IS FAIRLY LOW.
AVIATION
262000Z....COASTS/VALLEYS/COASTAL MOUNTAIN SLOPES...SCT-BKN CLOUDS
WITH BASES 3000-6000 FT MSL INTO THIS EVENING. MOUNTAIN TERRAIN WILL
BE OBSCURED IN CLOUDS, SIGNIFICANTLY REDUCING VISIBILITY. SCT TO ISO
RA EXPECTED ACROSS THE COASTAL BASIN THROUGH 02Z SUN. LOCAL VIS 3-5
MILES AND BASES LOCALLY AS LOW AS 1500-2500 FT MSL IN RA. THERE IS A
SLIGHT CHANCE (10-15%) OF ISO TS THROUGH 00Z SUN. ISO -RA POSSIBLE
OVERNIGHT INTO SUNDAY, MOST LIKELY NEAR COASTAL MOUNTAIN SLOPES.
CLEARING EXPECTED TO START AT THE COAST SUNDAY MORNING, WITH SCT-BKN
CONDITIONS POTENTIALLY LINGERING ALL AFTERNOON IN THE VALLEYS.
MOUNTAINS/DESERTS...AREAS OF WESTERLY WINDS WITH GUSTS 30-50 KT WILL
CONTINUE THROUGH TONIGHT, STRONGEST FROM THE MOUNTAIN CRESTS THROUGH
THE DESERT MOUNTAIN SLOPES. UP/DOWN DRAFTS EXPECTED OVER AND EAST OF
THE MOUNTAINS. PERIODIC GUSTS TO 30-35 KT THIS AFTERNOON/EVENING MAY
OCCUR AT PSP. ISO -RA/SN MAY LINGER INTO SUN AFTERNOON IN THE MTNS,
WITH WIDESPREAD TERRAIN OBSCURATIONS IN CLOUDS. A GRADUAL CLEARING
WILL OCCUR OVERNIGHT INTO SUNDAY MORNING.
MARINE
THERE IS A SLIGHT CHANCE (10-15 PERCENT)OF THUNDERSTORMS OVER THE
WATERS THIS AFTERNOON AND EVENING WHICH MAY BRING BRIEF HEAVY
RAINFALL, REDUCED VISIBILITY, ERRATIC WINDS, AND LIGHTNING. NO
HAZARDOUS MARINE CONDITIONS ARE EXPECTED SUNDAY THROUGH WEDNESDAY.
SGX WATCHES/WARNINGS/ADVISORIES
CA...WINTER WEATHER ADVISORY UNTIL 11 PM PDT THIS EVENING FOR
RIVERSIDE COUNTY MOUNTAINS-SAN BERNARDINO COUNTY MOUNTAINS.
WIND ADVISORY UNTIL 11 PM PDT THIS EVENING FOR APPLE AND LUCERNE
VALLEYS-SAN DIEGO COUNTY DESERTS-SAN GORGONIO PASS NEAR
BANNING.
BEACH HAZARDS STATEMENT FROM SUNDAY MORNING THROUGH WEDNESDAY
EVENING FOR ORANGE COUNTY COASTAL AREAS.
PZ...NONE.
PUBLIC...CSP
AVIATION/MARINE...CO
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