868
FXUS66 KSGX 280440
AFDSGX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
840 PM PST THU NOV 27 2025
SYNOPSIS
A COOLING TREND WILL DEVELOP FROM FRIDAY INTO THE WEEKEND, MOST
NOTABLY FOR THE MOUNTAINS AND WESTERN VALLEYS, AS HIGH PRESSURE
WEAKENS OVER THE REGION. LOW CLOUDS AND FOG WILL ALSO RETURN TO
THE COASTAL AREAS AND INLAND VALLEYS AS ONSHORE FLOW REPLACES THE
SANTA ANA WINDS. BY THE MIDDLE OF NEXT WEEK, AN AREA OF LOW
PRESSURE FROM THE NORTH WILL MOVE OVER THE DESERT SOUTHWEST.
THOUGH THE PATH OF THIS SYSTEM REMAINS UNCERTAIN, CHANCES OF
PRECIPITATION ARE IN THE FORECAST.
DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
THIS EVENING, SFC PRESSURE GRADIENTS ARE STILL WEAKLY OFFSHORE BUT
ARE TRENDING ONSHORE. THE UPPER LEVEL RIDGE HAS BEEN REPLACED BY
TROUGHING ALOFT. THE HEIGHT FALLS AND CYCLONIC FLOW ALOFT WILL
LIKELY CAUSE THE MARINE LAYER TO DEEPEN AS ONSHORE FLOW RETURNS.
PATCHES OF LOW CLOUDS HAVE FORMED OVER THE COASTAL WATERS AND HAVE
BEGUN TO MOVE ONSHORE IN NORTHERN SAN DIEGO COUNTY. HIGH CLOUDS
AND DRAINAGE WINDS COULD STILL DISRUPT THE FORMATION OF LOW CLOUDS
SO THERE ISN'T MUCH CONFIDENCE THAT WE'LL SEE MUCH LOW CLOUD
COVERAGE OR FOG TONIGHT, ALTHOUGH HIGH RESOLUTION MODELS INDICATE
SIGNIFICANT CLOUD COVER BY SUNRISE FRIDAY.
FROM PREVIOUS DISCUSSION...
A WEATHER SYSTEM CURRENTLY IN THE PACIFIC NORTHWEST WILL CONTINUE
TO PUSH INLAND OVER THE WESTERN PART OF THE COUNTRY, WEAKENING AND
DISPLACING THE AREA OF HIGH PRESSURE OVER OUR REGION THROUGH THE
WEEKEND. THIS WILL LEAD TO COOLER WEATHER WITH STRONGER ONSHORE
FLOW. BY THE WEEKEND, TEMPERATURES IN MOST AREAS WILL BE IN THE
60S AND 70S, WITH 50S ACROSS AREAS ABOVE 5,000 FEET. CHANCES FOR
LOW CLOUDS AND FOG WILL INCREASE OVER COASTAL AREAS INTO THE
WEEKEND AS THE MARINE LAYER DEEPENS.
A LOW PRESSURE SYSTEM WILL MOVE ACROSS THE GREAT BASIN BY SUNDAY
AND MONDAY, WHICH WILL LEAD TO A SLIGHT INCREASE IN OFFSHORE WINDS
FOR MONDAY. DEPENDING ON THE STRENGTH OF THIS PRESSURE GRADIENT,
TEMPERATURES MAY CLIMB INTO THE MID OR EVEN UPPER 70S FOR VALLEYS
WEST OF THE MOUNTAINS. A SECOND WEATHER SYSTEM WILL MOVE IN FROM
THE NORTH AROUND WEDNESDAY OF NEXT WEEK. MODEL PROJECTIONS SHOW
QUITE A VARIED ARRAY OF WHERE THE SYSTEM WILL GO. SOME PROJECTIONS
POINT TO A MORE INLAND SCENARIO, WHERE WE WOULD REMAIN DRY WITH
SANTA ANA WINDS. OTHERS POINT TO A WETTER SCENARIO, WHERE THE
SYSTEM MOVES CLOSER TO OUR AREA OR OFF THE OCEAN. NBM SHOWS
INCREASING CHANCES FOR PRECIPITATION AROUND 15-30% BY WEDNESDAY
AND THURSDAY OF NEXT WEEK. CONTINUE TO KEEP AN EYE ON THE FORECAST
AS OUR CONFIDENCE GROWS ON THE PATH OF THIS WEATHER SYSTEM AND
HOW IT COULD IMPACT YOUR AREA.
AVIATION
280345Z....COASTS/VALLEYS...SCT-BKN HIGH CLOUDS AOA 20,000FT MSL
ALONG WITH PATCHY CLOUD COVER, MOSTLY OFFSHORE, THIS EVENING. LOW
CLOUD COVER BASED 400-700 FT MSL WILL GRADUALLY SPREAD INTO PARTS OF
THE COAST OVERNIGHT, WITH A 40-60% CHANCE FOR CIGS AT COASTAL SITES
OVERNIGHT (HIGHEST CHANCES AFTER 08Z KSAN, 10Z KCRQ, AND 14Z KSNA).
LOCALIZED VIS REDUCTIONS DOWN TO 3-5SM POSSIBLE DURING THIS TIME AS
WELL, 0-2 SM FOR ELEVATED COASTAL TERRAIN IMPACTED BY CLOUDS. ANY
LOW CLOUDS CLEARING TO THE COAST 15-17Z, EXCEPT FOR PARTS OF
NORTHERN ORANGE CO WHERE CLOUDS COULD PERSIST THROUGH 18Z. MORE
WIDESPREAD LOW CLOUDS 600-900 FT MSL SPREADING INTO COASTAL AREAS UP
TO 15 MILES FROM SHORE AFTER SAT 02Z.
MOUNTAINS/DESERTS
VFR CONDITIONS EXPECTED THROUGH THE TAF
PERIOD. HIGH CLOUDS SCT-BKN AOA 20,000FT MSL THROUGH TONIGHT.
MARINE
NO HAZARDOUS MARINE CONDITIONS ARE EXPECTED THROUGH TUESDAY.
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...PG
AVIATION/MARINE...CSP
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