466
FXUS66 KSGX 180436
AFDSGX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
836 PM PST TUE DEC 17 2024
SYNOPSIS
ABOVE NORMAL TEMPERATURES WILL CONTINUE THROUGH THE REST OF THE
WEEK, WITH GUSTY SANTA ANA WINDS FROM THE FOOTHILLS TO THE
WESTERN VALLEYS THROUGH WEDNESDAY. A TROUGHING REGIME WILL SET UP
OFF THE WEST COAST LATER THIS WEEK, BRINGING A RETURN OF A DEEPER
MARINE LAYER, LOWER TEMPERATURES AND LIGHTER WINDS. THIS
TROUGHING PATTERN MAY STRENGTHEN ENOUGH TO BRING LIGHT
PRECIPITATION TO THE REGION EARLY NEXT WEEK.
DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
THIS EVENING, THE SANTA ANA WINDS HAVE PUSHED THE LOW CLOUDS MANY
MILES OFFSHORE TO THE SOUTHWEST, LEAVING ONLY HIGH CLOUDS
STREAMING FROM NORTH TO SOUTH OVERHEAD. WITHIN THE LAST HOUR, THE
WINDIEST LOCATIONS HAVE REPORTED WIND GUSTS OF 50 TO 65 MPH.
HIGHER GUSTS COULD OCCUR OVERNIGHT, MOST LIKELY IN THOSE SAME
LOCATIONS.
FROM PREVIOUS DISCUSSION...
WE CAN EXPECT THE SANTA ANA WINDS TO STRENGTHEN AND BECOME MORE
WIDESPREAD OVERNIGHT. HIGHEST WINDS WILL BE IN THE COASTAL FACING
PASSES WITH GUSTS LOCALLY OVER 50 MPH IN THE SANTA ANA MOUNTAINS
AND SAN BERNARDINO MOUNTAINS, LOCALLY OVER 40 MPH IN SAN DIEGO
COUNTY PER LATEST WRF/NBM MODEL GUIDANCE.
AS THE WINDS BEGIN TO BECOME MORE LOCALIZED LATER ON WEDNESDAY,
THE OFFSHORE WIND PATTERN WILL LEAD TO INCREASED TEMPERATURES OVER
THE REGION AS WELL. HIGH TEMPERATURES WILL BE UP TO LOCALLY 20
DEGREES ABOVE NORMAL FOR INLAND VALLEYS WEST OF THE MOUNTAINS BY
WEDNESDAY AFTERNOON, WITH MANY AREAS REACHING INTO THE LOW TO MID
80S. PLACES LIKE EL CAJON, LAKE ELSINORE AND CHINO HAVE ABOUT A
30-50% CHANCE OF REACHING THE 85 DEGREE MARK ON WEDNESDAY
AFTERNOON PER LATEST NBM PROBABILITIES. ONSHORE FLOW WILL RETURN
FOR THURSDAY INTO FRIDAY, HELPING TO DEEPEN THE MARINE LAYER AND
KNOCK TEMPERATURES DOWN SOME FOR THOSE WEST OF THE MOUNTAINS. THIS
WILL BRING A BETTER CHANCE OF LOW CLOUDS AND PATCHY FOG ACROSS
THE COASTAL AREAS EACH NIGHT AND MORNING AS WE APPROACH THE
WEEKEND.
BY THE WEEKEND, A TROUGHING PATTERN DEVELOPS OVER THE WEST COAST
AS WAVES OF PRECIPITATION ARE EXPECTED FOR PARTS OF NORTHERN
CALIFORNIA. THE JET STREAM MAY BECOME AMPLIFIED ENOUGH TO BRING
LIGHT PRECIPITATION TO PARTS OF SOCAL NEAR THE CHRISTMAS EVE TIME
FRAME AS SOME MODEL ENSEMBLE GUIDANCE SUGGESTS. NBM POPS LEFT IN
AS CHANCES FOR MEASURABLE RAINFALL LOOK SMALL FOR NOW (10-30%),
THOUGH ENSEMBLE CLUSTER ANALYSIS PAINTS A MORE DRIER RIDGING
PATTERN OVERALL. THIS LEADS TO A CONTINUED HIGH UNCERTAINTY
FORECAST, SO PLEASE KEEP UP WITH THE LATEST DETAILS AS WE HEAD
CLOSER TO THE CHRISTMAS HOLIDAY.
AVIATION
180400Z....COASTS/VALLEYS...FEW-SCT HIGH CLOUDS THROUGH TOMORROW.
GUSTY OFFSHORE WINDS WILL BE STRONGEST TONIGHT INTO EARLY WEDNESDAY
MORNING FOR PARTS OF THE INLAND VALLEYS AND COASTAL FOOTHILLS, THEN
DECREASE THROUGH WED. INTERMITTENTLY BREEZY WINDS AT KSNA AND KSBD
ARE POSSIBLE OVERNIGHT, WITH PERIODS OF CALMER WINDS WHERE LLWS
BECOMES A CONCERN. LOW CLOUDS BASED AT 300-700 FT MSL DEVELOP
OFFSHORE AFTER 01Z THU, BUT WITH CONTINUED WEAK OFFSHORE FLOW,
CHANCES FOR IMPACTS AT COASTAL SITES ARE GENERALLY LOW, WITH A 30%
CHANCE FOR BKN OR MORE CIGS AT KSAN 02-12Z THU AND 10% ELSEWHERE.
MOUNTAINS/DESERTS
FEW-SCT HIGH CLOUDS THROUGH WEDNESDAY
GENERALLY ABOVE 20,000FT MSL. NORTHEAST TO EAST WINDS GUSTING 25-35
KTS WITH MODERATE UP/DOWNDRAFTS OVER THE MOUNTAINS. BLDU POSSIBLE
AND MAY BRIEFLY REDUCE VIS DOWN TO 3SM. LOCALLY STRONGER SURFACE
WINDS THROUGH MOUNTAIN PASSES. LIGHTER WINDS AFTER 18Z WEDNESDAY.
MARINE
NO HAZARDOUS MARINE WEATHER CONDITIONS ARE EXPECTED THROUGH SATURDAY.
FIRE WEATHER
GUSTY NORTHERLY SANTA ANA WINDS WILL CONTINUE TO SPREAD INTO
FOOTHILLS AND VALLEYS OF ORANGE AND THE INLAND EMPIRE, A BIT LATER
INTO PARTS OF SAN DIEGO COUNTY. THE STRONG WINDS WILL CONTINUE
INTO WEDNESDAY MORNING, THEN GRADUALLY WEAKEN FOR WEDNESDAY
AFTERNOON AND EVENING.
THE STRONGER GUSTS ALONG AND BELOW THE COASTAL SLOPES OF THE SAN
BERNARDINO COUNTY MOUNTAINS AND ALONG AND BELOW THE COASTAL SLOPES
OF THE SANTA ANA MOUNTAINS ARE EXPECTED TO REACH 40 TO 50 MPH,
WITH THE STRONGER GUSTS ALONG AND BELOW THE COASTAL SLOPES OF THE
MOUNTAINS IN RIVERSIDE AND SAN DIEGO COUNTIES TO 30 TO 40 MPH. THE
MOST WIND-PRONE LOCATIONS COULD GET GUSTS OF 60-70 MPH.
THE LOWEST HUMIDITY ON WEDNESDAY FOR THE VALLEYS, INLAND COASTAL
AREAS, AND COASTAL SLOPES OF THE MOUNTAINS WILL FALL TO 10 TO 15
PERCENT. ONLY ISOLATED AREAS IN EITHER TIME OR SPACE MIGHT
BRIEFLY REACH RED FLAG CRITERIA FOR WEDNESDAY AFTERNOON WITH THE
MOST LIKELY LOCATIONS FOR THAT TO OCCUR BEING IN THE INLAND
EMPIRE BELOW THE CAJON PASS AND BANNING PASS.
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/FIRE WEATHER...PG
AVIATION/MARINE...CSP
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