554
FXUS66 KSGX 162129
AFDSGX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
130 PM PST MON DEC 16 2024
SYNOPSIS
FAIR AND WARMER WEATHER WILL PREVAIL THIS WEEK WITH THE WARMEST DAYS
WEDNESDAY AND THURSDAY. WEAK TO MODERATE SANTA ANA WINDS WILL
DEVELOP TUESDAY AND CONTINUE THROUGH WEDNESDAY, WITH WEAKER WINDS
THURDSAY THROUGH SATURDAY. A COOLING TREND WILL OCCUR FRIDAY THROUGH
SUNDAY.
DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...
SKIES WERE MOSTLY SUNNY EXCEPT FOR A FEW HIGH CLOUDS AT EARLY
AFTERNOON. AFTER A CHILLY START THIS MORNING, TEMPERATURES WERE IN
THE UPPER 60S TO MID 70S WEST OF THE MOUNTAINS AND MOSTLY MID 70S IN
THE LOWER DESERTS. BOUNDARY LAYER MOISTURE INCREASES SOMEWHAT NEAR
THE COAST OVERNIGHT WHICH COULD LEAD TO PATCHY LOW CLOUDS AND FOG
NEAR THE IMMEDIATE COAST/COASTAL WATERS, BUT NOTHING WIDESPREAD.
A TROUGH OF LOW PRESSURE WILL MOVE THROUGH THE PAC NW AND NORTHERN
CALIFORNIA THE REST OF TODAY, BUT DRY ZONAL FLOW WILL PREVAIL IN
SOUTHERN CALIFORNIA. THE TROUGH WILL RAPIDLY MOVE EAST TO THE
NORTHERN/CENTRAL ROCKIES AND PLAINS TUESDAY AND DEEPEN, WHILE A
RIDGE WILL DEVELOP OVER THE WEST COAST. OFFSHORE FLOW WILL DEVELOP,
MOSTLY DRIVEN BY A DISTANT SURFACE HIGH OVER THE ID/WY BORDER, WITH
UP TO 20 MB MSLP GRADIENT TO SAN DIEGO. THIS, COMBINED WITH MODERATE
COLD AIR ADVECTION AROUND 850 MB WILL BRING MODERATE NORTHEASTERLY
WINDS TO THE REGION. THIS WILL BE PRIMARILY AN MSLP GRADIENT DRIVEN
WIND SO MOUNTAIN WAVE ACTIVITY WILL BE MORE LIMITED. PEAK GUSTS
SHOULD BE 35-50 MPH IN MOST OF THE WINDIER AREAS, SUCH AS FROM CAJON
PASS SOUTH THROUGH A RIBBON OF THE INLAND EMPIRE AND TO THE SANTA
ANA MOUNTAINS, PLUS A FEW LOCATIONS ON THE WESTERN SLOPES OF THE SAN
DIEGO COUNTY MOUNTAINS. HUMIDITY WILL BE LOW MOST OF THIS WEEK, WITH
LOWEST HUMIDITY 10-20 PERCENT WEDNESDAY.
THE UPPER HIGH WILL SHIFT EAST TO THE ROCKIES/PLAINS LATE IN THE
WEEK WITH A BROAD DEEP TROUGH OVER THE NE PACIFIC. THAT TROUGH WILL
BRING PRECIPITATION TO MUCH OF THE WEST COAST, BUT AGAIN WE WILL BE
TOO FAR SOUTH WITH THIS ROUND. REGARDLESS, WE WILL HAVE A GRADUAL
COOLING TREND FRIDAY-SUNDAY. LONGER-TERM GUIDANCE FOR THE WEEK OF
XMAS HAS THE STORM TRACK MOSTLY STAYING TO OUR NORTH, BUT AROUND 30-
40% OF ENSEMBLE MEMBERS HAVE AT LEAST A SMALL AMOUNT OF PRECIP IN
OUR AREA AROUND XMAS.
AVIATION
162100Z....COASTS...MOSTLY CLEAR WITH UNRESTRICTED VIS THROUGH LATE
TONIGHT. PATCHY LOW CLOUDS LOOK TO DEVELOP OVER THE NEARSHORE WATERS
AROUND 04-07Z TONIGHT, BUT THERE IS ONLY A LOW CHANCE OF THEM MAKING
IT BRIEFLY INTO COASTAL SITES. KSAN HAS THE BEST CHANCE OF CIGS AT
20-30% FROM 09-13Z TUESDAY MORNING, WITH MUCH LOWER CHANCES (5-10%)
FOR SITES IN NORTH SD AND ORANGE COUNTIES. BASES FOR ANY CLOUDS THAT
SNEAK ASHORE WOULD BE AT ABOUT 500-900FT MSL, WITH LOCALIZED AREAS
OF BR 3-5 SM OVER HIGHER COASTAL TERRAIN.
VALLEYS/MOUNTAINS/DESERTS
MOSTLY CLEAR EXCEPT FOR HIGH CLOUDS AT
OR ABOVE 25,000 FT MSL WITH UNRESTRICTED VIS THROUGH TUESDAY
AFTERNOON.
MARINE
STRONGER NORTHWEST WINDS EXPECTED TO PICK UP IN THE OUTER COASTAL
WATERS LATER THIS AFTERNOON, TAPERING OFF TUESDAY MORNING. ISOLATED
GUSTS 20-25 KTS POSSIBLE, PRIMARILY NEAR SAN CLEMENTE ISLAND.
OTHERWISE, NO HAZARDOUS MARINE WEATHER EXPECTED THROUGH SATURDAY.
FIRE WEATHER
SANTA ANA WINDS WILL DEVELOP TUESDAY, PEAKING TUESDAY NIGHT AND
WEDNESDAY MORNING THEN GRADUALLY DIMINISHING WEDNESDAY MIDDAY
THROUGH AFTERNOON. 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. 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 WILL
SLOWLY SUBSIDE WEDNESDAY NIGHT AND THURSDAY.
MINIMUM RELATIVE HUMIDITY TUESDAY WILL BE 15-20 PERCENT IN THE
VALLEYS AND FOOTHILLS, LOWERING TO 10-20 PERCENT WEDNESDAY IN ALL
AREAS EXCEPT THE COAST, WITH ONLY SMALL IMPROVEMENTS 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 LOCALLY NEAR CRITICAL FIRE WEATHER
CONDITIONS WILL OCCUR TUESDAY THROUGH THURSDAY. THERE COULD BE AT
LEAST A FEW HOURS OF CRITICAL FIRE WEATHER CONDITIONS WEDNESDAY
MORNING THROUGH EARLY 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/FIRE WEATHER...MAXWELL
AVIATION/MARINE...MUNYAN
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