781
FXUS66 KSGX 160440
AFDSGX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
840 PM PST SUN DEC 15 2024
SYNOPSIS
WARM AND DRY THIS WEEK WITH WEAK TO MODERATE SANTA ANA WINDS
TUESDAY THROUGH THURSDAY. LIGHTER WINDS AND A GRADUAL COOLING
FRIDAY THROUGH NEXT SUNDAY.
DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
EVENING UPDATE...
SKIES ARE CLEAR THIS EVENING WITH LIGHT OFFSHORE FLOW NEAR THE
PASSES AND FOOTHILLS WHERE GUSTS ARE CURRENTLY AROUND 20-30 MPH.
SURFACE PRESSURE GRADIENTS ARE TRENDING OFFSHORE, CURRENTLY -7 MB
SAN-TPH AND -2.3 MB SAN-DAG. GRADIENTS AND RESULTING WINDS ARE
FORECAST TO PEAK THIS EVENING BEFORE SLOWLY WEAKENING OVERNIGHT,
FOLLOWED BY A RETURN OF WEAK ONSHORE FLOW MONDAY AFTERNOON. A
WARMING TREND WILL BEGIN MONDAY AS A WEAK UPPER LEVEL RIDGE OF
HIGH PRESSURE SHIFTS EASTWARD OVER THE DESERT SOUTHWEST AS IT
FLATTENS OUT AHEAD OF AN UPPER TROUGH APPROACHING THE PACIFIC
NORTHWEST. THE ONLY CHANGE TO THE FORECAST THIS EVENING WAS TO ADD
PATCHY FOG TO THE COASTAL AREAS MONDAY NIGHT INTO EARLY TUESDAY
MORNING.
PREVIOUS DISCUSSION...
THE UPPER LEVEL LOW WILL SHIFT EAST THROUGH THE NORTHERN ROCKIES
AND NORTHERN PLAINS TUESDAY AS ANOTHER RIDGE FORMS ALONG THE WEST
COAST. THIS WILL COMBINE WITH A STRONG SURFACE HIGH OVER THE
NORTHERN ROCKIES WITH A 15-20 MB MSLP GRADIENT, ALBEIT OVER A
BROAD AREA INSTEAD OF CONCENTRATED OVER THE SOCAL MOUNTAINS. SAME
THING WITH THE COLD AIR ADVECTION AT 850 MB WITH MODERATE AMOUNTS
FROM CENTRAL NV THROUGH SOCAL, BUT NOTHING EXTREME. THUS, WE
SHOULD HAVE WEAK TO MODERATE SANTA ANA WINDS TUE-THU, STRONGEST
TUE NIGHT/WED MORNING. HIGH RESOLUTION GUIDANCE SUGGESTS GUSTS 35
TO 50 MPH IN WINDIEST LOCATIONS OF THE SAN BERNARDINO COUNTY
MOUNTAINS TUE NIGHT/WED MORNING, BELOW CAJON PASS AND THE SANTA
ANA MOUNTAINS, AND IN A FEW PARTS OF THE SAN DIEGO COUNTY
MOUNTAINS WED. WITH THE UPPER RIDGE, TEMPERATURES SHOULD BE QUITE
HIGH COMPARED TO NORMAL, WITH SOME LOWER 80S AT LOWER ELEVATIONS,
BOTH IN THE LOWER DESERTS AND VALLEYS.
LATE IN THE WEEK, THE RIDGE WILL MOVE EAST TOWARDS THE ROCKIES
AND/OR PLAINS, THOUGH MODELS/ENSEMBLES HAVE A LOT OF VARIATION IN
THE TROUGH DEVELOPING OFF THE WEST COAST, ESPECIALLY THE SOUTHWARD
EXTENT. MOST LIKELY, THE PRECIPITATION WILL STAY NORTH OF POINT
CONCEPTION WITH THE TROUGH NEXT WEEKEND. BEYOND THAT, THE GENERAL
PATTERN OF THE STORM TRACK HAS PRECIPITATION EVERY FEW DAYS OVER
NORTHERN/CENTRAL CALIFORNIA, BUT WITH LOW CONFIDENCE (BUT NOT ZERO)
FOR ANY PRECIPITATION IN FAR SOUTHERN CALIFORNIA THE WEEK OF
CHRISTMAS.
AVIATION
160435Z....MOSTLY CLEAR WITH UNRESTRICTED VIS THROUGH MONDAY
AFTERNOON.
MARINE
STRONGER NORTHWEST WINDS EXPECTED IN THE OUTER COASTAL WATERS
STARTING MONDAY AFTERNOON, WITH ISOLATED GUSTS 20-25 KTS NEAR SAN
CLEMENTE ISLAND MONDAY EVENING THROUGH EARLY TUESDAY MORNING.
OTHERWISE, NO HAZARDOUS MARINE WEATHER EXPECTED THROUGH FRIDAY.
FIRE WEATHER
SANTA ANA WINDS WILL DEVELOP TUESDAY, PEAKING TUESDAY NIGHT AND
WEDNESDAY MORNING FOR ORANGE, SAN BERNARDINO, AND RIVERSIDE
COUNTIES, AND LATE WEDNESDAY MORNING INTO WEDNESDAY AFTERNOON FOR
SAN DIEGO COUNTY. PEAK GUSTS ARE CURRENTLY PROJECTED IN THE 35-50
MPH RANGE THROUGH AND BELOW CAJON PASS AND ADJACENT COASTAL
SLOPES OF THE SAN BERNARDINO COUNTY MOUNTAINS, PARTS OF THE INLAND
EMPIRE AND IN THE SANTA ANA MOUNTAINS AND FOOTHILLS. PEAK WINDS
WILL BE CLOSER TO 30-40 MPH FOR MUCH OF THE SAN DIEGO COUNTY
MOUNTAINS AND FOOTHILLS, WITH ISOLATED GUSTS TO 50 MPH ON THE
FAVORED COASTAL SLOPES. WINDS FOR ALL LOCATIONS WILL SLOWLY
SUBSIDE WEDNESDAY NIGHT INTO THURSDAY.
MINIMUM RELATIVE HUMIDITY ON TUESDAY WILL BE AROUND 20 PERCENT FOR
THE VALLEYS AND FOOTHILLS, LOWERING TO 15-20 PERCENT ON WEDNESDAY
FOR ALL AREAS EXCEPT THE COAST, WITH ONLY SMALL IMPROVEMENTS ON
THURSDAY. MODERATE TO POOR OVERNIGHT RECOVERY IS EXPECTED NEAR
THE PASSES AND FOOTHILLS EACH NIGHT TUESDAY THROUGH THURSDAY.
WITH THE COMBINATION OF ABOVE NORMAL TEMPERATURES, LOW HUMIDITY,
AND GUSTY OFFSHORE WINDS, ELEVATED TO NEAR CRITICAL FIRE WEATHER
CONDITIONS WILL OCCUR TUESDAY THROUGH THURSDAY. THERE WILL LIKELY
BE AT LEAST A FEW HOURS OF CRITICAL FIRE WEATHER CONDITIONS
WEDNESDAY MORNING THROUGH EARLY WEDNESDAY AFTERNOON IN THE WIND
PRONE AREAS.
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...SS/MAXWELL
FIRE WEATHER...SS
AVIATION/MARINE...PG
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