163
FXUS66 KSGX 120449 AAA
AFDSGX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
943 PM PDT SUN APR 11 2021
SYNOPSIS
COOLING WILL INTENSIFY MONDAY AND TUESDAY IN RESPONSE TO A LOW
PRESSURE SYSTEM DEVELOPING OVER THE NORTHERN GREAT BASIN. THIS WILL
ENHANCE ONSHORE FLOW ACROSS THE REGION, BRINGING GUSTY WINDS TO
DESERT SLOPES AND PASSES MONDAY THROUGH WEDNESDAY (STRONGEST
TUESDAY), AND A DEEPER MARINE LAYER. THE LATTER SHOULD BE SUFFICIENT
TO GENERATE SOME SPRINKLES ACROSS THE COASTAL BASIN MONDAY NIGHT
INTO EARLY TUESDAY MORNING, AND POSSIBLY AGAIN TUESDAY NIGHT, WITH
MINIMAL ACCUMULATIONS EXPECTED. THURSDAY WILL SEE US RETURN TO A
WARMING TREND THAT WILL CONTINUE INTO THE WEEKEND, WITH SHALLOWER
MARINE LAYER CLOUDS EACH NIGHT/MORNING AT THE COAST.
DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
EVENING UPDATE:
THE ONSHORE GRADIENTS ARE SLOWLY INCREASING THIS EVENING AND A
HEALTHY CATALINA EDDY HAS HELPED TO DEEPEN THE MARINE LAYER AND
PRODUCE ABUNDANT COASTAL STRATUS, NOW QUICKLY PUSHING INTO THE
WESTERN VALLEYS THIS EVENING. THE FORECAST WAS UPDATED EARLIER TO
SPREAD THE CLOUDS FASTER AND FURTHER INLAND THROUGH THE REMAINDER OF
THE NIGHT. NO OTHER UPDATES WERE NEEDED AT THIS TIME.
PREVIOUS DISCUSSION, ISSUED AT 137 PM PDT:
HIGH CLOUDS ARE ABUNDANT TODAY, SHIELDING US FROM BRIGHTER SKIES AND
KEEPING TEMPERATURES A LITTLE MORE IN CHECK COMPARED TO PREVIOUS
DAYS. IT'S RELATIVELY MILD NONETHELESS, WITH INLAND AREAS
(ESPECIALLY THE MOUNTAINS AND DESERTS) STILL A FEW DEGREES ABOVE
NORMAL. LOW CLOUDS WILL AGAIN FILL THE COASTAL BASIN TONIGHT,
EXTENDING FAR INTO THE VALLEYS AS A COASTAL EDDY AND TIGHTENING
ONSHORE PRESSURE GRADIENTS FORCE SOME DEEPENING.
WITH A LOW PRESSURE SYSTEM DROPPING SOUTHWARD TOWARD THE NORTHERN
GREAT BASIN MONDAY INTO TUESDAY, BELOW NORMAL TEMPERATURES WILL
FINALLY MAKE A RETURN. GUSTY WEST WINDS WILL FOLLOW SUIT, IMPACTING
DESERT SLOPES AND EAST-WEST FACING PASSES THROUGH WEDNESDAY, AND
PEAKING ON TUESDAY WHEN THEY'LL LIKELY REACH ADVISORY LEVELS WITH
GUSTS 35 TO 50 MPH, LOCALLY HIGHER.
BY MONDAY NIGHT, THE MARINE LAYER WILL HAVE DEEPENED ENOUGH TO ALLOW
FOR PATCHY DRIZZLE OR BRIEF LIGHT SHOWERS ACROSS MUCH OF THE COASTAL
BASIN AND INTO THE WINDWARD MOUNTAIN SLOPES. ACCUMULATIONS, IF ANY,
WILL BE LIGHT AND MEASURED IN HUNDREDTHS OF AN INCH, TAPERING OFF IN
THE MORNING. A SIMILAR SCENARIO MAY PLAY OUT TUESDAY NIGHT INTO
EARLY WEDNESDAY MORNING. TUESDAY AND WEDNESDAY WILL BE SIMILARLY
COOL, WITH HIGHS THAT WILL STRUGGLE TO REACH 70 ANYWHERE OUTSIDE OF
THE DESERTS.
AND THAT, FOLKS, WILL BE THE EXTENT OF THIS TEASER. IT WILL BE A
WELCOME CHANGE FOR MANY, BRINGING PLEASANTLY COOL TEMPERATURES FOR
HIKING, THOUGH CERTAINLY NOT IDEAL BEACH WEATHER. OUR VEGETATION
WOULD CERTAINLY APPRECIATE SOME MEANINGFUL PRECIPITATION AS WE INCH
CLOSER TO THE CLIMATOLOGICAL END TO OUR RAINY SEASON (AND ALSO AN
ALMOST GUARANTEED EARLY START TO HIGH FIRE SEASON), BUT THAT'S NOT
ON THE TABLE AS IT STANDS. AS THE GREAT BASIN LOW DISSIPATES, ZONAL
FLOW WILL GRADUALLY TRANSITION TO WEAK RIDING AS WE NEAR THE
WEEKEND. TEMPERATURES WILL BEGIN TO WARM STARTING THURSDAY, AND THE
WARMING TREND WILL LAST THROUGH AT LEAST SUNDAY, BY WHICH TIME WE
SHOULD RETURN TO WARMER THAN AVERAGE CONDITIONS AS HIGHS IN THE 80'S
MAKE A COMEBACK TO THE INTERIOR. COASTAL LOW CLOUDS WILL CONTINUE
EACH NIGHT AND MORNING, BUT WILL BE CONSIDERABLY SHALLOWER DURING
THE LATTER HALF OF THE WEEK.
AVIATION
120405Z...COAST/VALLEYS...LOW CLOUDS INCREASING IN COVERAGE AND
SPREADING UP TO 20 MILES INLAND OVERNIGHT, LIKELY REACHING KONT
AROUND 09Z. EXPECT CIGS 1200-1800 FT MSL AT COASTAL TAF SITES WITH
TOPS TO 2200 FT MSL OBSCURING HIGHER TERRAIN. LOCAL VIS 1-3 MILES
WILL OCCUR IN THE VALLEYS THROUGH 16Z MON. CLEARING FROM INLAND TO
THE COAST EXPECTED 16Z-19Z MON. OTHERWISE, MOSTLY SCT CLOUDS
AT/ABOVE 20000 FT MSL THROUGH MON MORNING.
MOUNTAINS/DESERTS...MOSTLY SCT CLOUDS AT/ABOVE 20000 FT MSL WITH
UNRESTRICTED VIS THROUGH MON MORNING.
MARINE
WEST-NORTHWEST WINDS WITH GUSTS TO 20 KNOTS WILL OCCUR EACH
AFTERNOON AND EVENING IN THE OUTER WATERS THROUGH MONDAY. STRONGEST
WINDS WILL BE NEAR SAN CLEMENTE ISLAND. OTHERWISE, NO HAZARDOUS
MARINE WEATHER IS EXPECTED THROUGH FRIDAY.
SKYWARN
SKYWARN ACTIVATION IS NOT REQUESTED. HOWEVER WEATHER SPOTTERS ARE
ENCOURAGED TO REPORT SIGNIFICANT WEATHER CONDITIONS.
SGX WATCHES/WARNINGS/ADVISORIES
CA...NONE.
PZ...NONE.
SYNOPSIS/PUBLIC DISCUSSION...RODRIGUEZ/JMB
AVIATION/MARINE...PG
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