207
FXUS66 KSGX 191132
AFDSGX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
432 AM PDT SAT SEP 19 2026
SYNOPSIS
TEMPERATURES REMAIN BELOW NORMAL INTO WEDNESDAY WITH A PRESENT
MARINE LAYER. WARMER WEATHER RETURNS FOR THE END OF NEXT WEEK AS
HIGH PRESSURE BUILDS.
DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
..UPDATED AVIATION DISCUSSION
THE 00Z SOUNDING FRIDAY AFTERNOON SHOWS A WELL MIXED MARINE BOUNDARY
LAYER, AROUND 3000 FEET DEEP. LOW CLOUDS WILL BE PATCHY OVERNIGHT
THROUGH THE COASTAL BASIN AND SCATTER OUT TO THE COAST BETWEEN 8-11
AM THIS MORNING.
WHILE THE COASTAL BASIN WILL MAINTAIN MODEST MINIMUM RELATIVE
HUMIDITY VALUES (30-60% INLAND, 60-80% COAST) THIS AFTERNOON,
CONDITIONS WILL BE VERY DRY FOR HIGHER MOUNTAIN COMMUNITIES AND
EASTWARD INTO THE DESERTS, DROPPING TO 8-15%. THESE LOW DAYTIME
HUMIDITIES IMPROVE FOR MOUNTAINS/DESERTS THROUGH MONDAY AFTERNOON
WITH MORE TYPICAL MINIMUM RH VALUES DOWN TO 15-30%.
THE CLOSED UPPER LOW OVER IDAHO CONTINUES TO TREK EASTWARD AND IS
BEING REPLACED BY A SHORTWAVE RIDGE, BUMPING UP OUR TEMPERATURES
THIS AFTERNOON BY 3-6 DEGREES RELATIVE TO YESTERDAY. THE RIDGE MOVES
OUT OF THE REGION QUICKLY AS ANOTHER CLOSED LOW APPROACHES FROM THE
WEST SUNDAY, CENTERING OVER CENTRAL CALIFORNIA BY MONDAY.
TEMPERATURES ONCE AGAIN DROP TO 6-12 DEGREES BELOW AVERAGE ACROSS
INLAND AREAS MONDAY AS THE MARINE LAYER DEEPENS AND LOW CLOUDS FILL
THE COASTAL BASIN DURING THE NIGHTS AND EARLY MORNINGS OF EARLY NEXT
WEEK.
THE UPPER CLOSED LOW WEAKENS AND COMBINES WITH THE MAIN JET STREAM
IN THE NORTHERN ROCKIES, LEAVING BEHIND VERY WEAK HIGHER PRESSURE
ANOMALIES OVER THE EASTERN GREAT BASIN AND THUS PERHAPS A VERY
WEAK N/E LOW LEVEL OFFSHORE PRESSURE GRADIENT WEDNESDAY (~20%
CHANCE). THE EXTENT OF THE EFFECTS WOULD BE LIMITED TO HOW DRY THE
AIR WOULD BE THROUGH THE DESERTS AND MOUNTAINS AND THUS HOW MUCH
THE DAYTIME TEMPERATURES COULD SPIKE FOR INLAND LATER IN THE WEEK.
WITH THE TROUGH ALREADY MOVING OUT, TEMPERATURES ARE ALREADY
FORECAST TO JUMP UP 5-10 DEGREES INTO WEDNESDAY WITH HIGHS LATER
IN THE WEEK (INCLUDING WEDNESDAY) REACHING BACK INTO THE LOW-100S
IN THE LOW DESERTS, MID-90S IN THE IE, MID/UPPER 80S INLAND AND
AROUND 80 FOR COASTAL AREAS. THESE ARE ALL TEMPERATURES TYPICAL
FOR MID-SEPTEMBER, THOUGH MAYBE A FEW DEGREES ABOVE AVERAGE AT THE
COAST.
BEYOND, WPC MODEL CLUSTERS ARE CONVERGING ON SOLUTIONS SHOWING
ANOTHER TROUGH DEVELOPING OFF OF THE WEST COAST BY NEXT WEEKEND.
THE AMPLITUDE AND INTENSITY OF THIS TROUGH ARE UNCERTAIN, AND
THERE IS THUS UNCERTAINTY ABOUT WHETHER TEMPERATURES STAY NEAR
AVERAGE OR DIP BELOW AVERAGE AGAIN.
AVIATION
191130Z...COAST/VALLEYS...LOW CLOUDS BASED 2000-3000FT MSL WILL BE
INTERMITTENT FOR PARTS OF THE INLAND EMPIRE AND ORANGE COUNTY THIS
MORNING. LOW TO MODERATE CONFIDENCE ON CIGS COVERING KONT AND KSNA
THIS MORNING BETWEEN 13-16Z. CLEARING FROM VALLEYS TO COAST 16-18Z.
CIGS SLIGHTLY LOWER 1500-2500 FT MSL TONIGHT INTO SUNDAY MORNING.
LOW CLOUDS PUSHING ASHORE 02-04Z SUNDAY WITH LOWER CONFIDENCE ON
CIGS COVERING AREAS OF THE INLAND EMPIRE AFTER 12Z SUN.
MOUNTAINS/DESERTS...MOSTLY CLEAR AND VFR CONDITIONS THROUGH THE
WEEKEND.
MARINE
NO HAZARDOUS MARINE CONDITIONS ARE EXPECTED THROUGH WEDNESDAY.
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...WESTERINK
AVIATION/MARINE...APR
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