639  
FXUS66 KSGX 081044  
AFDSGX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE SAN DIEGO CA  
244 AM PST SAT FEB 8 2025  
   
SYNOPSIS
 
 
DRIER AND A LITTLE WARMER THIS WEEKEND WITH WEAK OFFSHORE FLOW.  
THE MARINE LAYER RETURNS MONDAY, DEEPENING INTO TUESDAY WITH SMALL  
CHANCES OF LIGHT PRECIPITATION ACROSS THE COASTS AND VALLEYS. A  
MUCH MORE SIGNIFICANT PRECIPITATION EVENT IS LIKELY LATE  
WEDNESDAY THROUGH LATE FRIDAY, WITH THE GREATEST CHANCES THURSDAY  
INTO FRIDAY.  
 

 
   
DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE
 
 
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO  
COUNTIES...  
 
KEY MESSAGES:  
 
- WARMER AND DRIER THIS WEEKEND WITH WEAK NORTHERLY TO  
NORTHEASTERLY WINDS BELOW THE PASSES EACH MORNING.  
 
- 10-15% CHANCE OF LIGHT PRECIPITATION FOR THE COASTAL AREAS AND  
SAN DIEGO VALLEYS LATE MONDAY NIGHT INTO TUESDAY MORNING.  
 
- 20-40% CHANCE OF LIGHT PRECIPITATION WEDNESDAY, THEN WIDESPREAD  
MODERATE TO HEAVY PRECIPITATION LIKELY (70-80% CHANCE) THURSDAY  
INTO EARLY FRIDAY AS AN ATMOSPHERIC RIVER MOVES INTO SOUTHERN  
CA.  
 
AREAS OF LOW CLOUDS CONTINUE WEST OF THE MOUNTAINS THIS MORNING.  
WHERE ENOUGH CLEARING OCCURS, SHALLOW PATCHY FOG COULD DEVELOP,  
DISSIPATING BY MID MORNING. OTHERWISE SCATTERED HIGH CLOUDS ARE  
MOVING ACROSS THE REGION. SURFACE PRESSURE GRADIENTS ARE BEGINNING  
TO TREND OFFSHORE, CURRENTLY AROUND 1.5 MB SAN-TPH. AS THIS TREND  
CONTINUES, WEAK NORTHERLY TO NORTHEASTERLY WINDS WILL DEVELOP  
BELOW THE PASSES AND CANYONS WITH LOCAL GUSTS TO AROUND 35 MPH.  
SLIGHTLY STRONGER OFFSHORE WINDS WILL DEVELOP FOR SUNDAY MORNING  
AS GRADIENTS INCREASE, BUT WINDS WILL STILL REMAIN CONFINED TO  
THE FAVORED PASSES AND CANYONS. OTHERWISE GRADUAL WARMING AND  
DRYING THROUGH THE WEEKEND WITH HIGHS NEAR NORMAL TODAY, AND  
AROUND 3-8 DEGREES ABOVE NORMAL ON SUNDAY, WITH THE GREATEST  
DEPARTURE FROM NORMAL IN THE INLAND VALLEYS.  
 
A WEAK AND DRY UPPER LEVEL TROUGH MOVES THROUGH MONDAY MORNING,  
HELP BRINGING A RETURN OF MARINE LAYER LOW CLOUDS AND FOG ALONG  
THE COAST AND BREEZY ONSHORE FLOW. FOG MAY BE BRIEFLY DENSE AS LOW  
CLOUDS DEVELOP LATE SUNDAY NIGHT, THOUGH CONDITIONS SHOULD  
IMPROVE QUICKLY AS THE MARINE LAYER DEEPENS. THIS TREND CONTINUES  
ON TUESDAY AS ANOTHER SHORT WAVE MOVES THROUGH THE MEAN TROUGH.  
MOISTURE REMAINS LIMITED, AND DESPITE NBM POPS OF 15-25% ACROSS  
AREAS ALONG AND WEST OF THE MOUNTAINS, IT LOOKS LIKE WE'LL ONLY  
SEE MARINE LAYER DRIZZLE AT BEST WITH LITTLE TO NO ACCUMULATION.  
 
ATTENTION QUICKLY TURNS TO THE IMPENDING ATMOSPHERIC RIVER (AR)  
FOR THE LATTER HALF OF THE WEEK. DEEPER MOISTURE WITH IVT IN  
EXCESS OF 250 KG/M/S BEGINS TO OVERSPREAD THE REGION BY WEDNESDAY  
MORNING, THOUGH FORCING IS LIMITED AS WE REMAIN UNDER WEAKLY  
CYCLONIC FLOW OR EVEN WEAK RIDGING (24% OF THE ENSEMBLE SPACE).  
GIVEN THIS, ANY PRECIPITATION WEDNESDAY WOULD LIKELY BE LIGHT FOR  
THE COASTAL BASIN, THOUGH SUFFICIENT OROGRAPHIC LIFT WILL EXIST  
FOR HIGHER RAINFALL AMOUNTS ON THE COASTAL MOUNTAIN SLOPES. IVT  
PEAKS THURSDAY AFTERNOON INTO FRIDAY MORNING AHEAD OF A DEEPENING  
UPPER LEVEL LOW. WHILE THERE IS STILL A LOT OF SPREAD IN THE IVT  
FORECASTS FROM THE GEFS AND EPS, ENSEMBLE MEANS POINT TO A WEAK  
(GEFS) TO MODERATE (EPS) AR. GIVEN THE MUCH STRONGER DYNAMICS AND  
HIGHER IVT, EXPECT CONSIDERABLY MORE RAINFALL THAN THE EVENT WE  
JUST HAD. WHILE UNCERTAINTY IN EXACT AMOUNTS STILL EXISTS, THE NBM  
CURRENTLY HAS A 65-85% CHANCE OF AT LEAST 1" OF STORM TOTALS  
PRECIPITATION ACROSS THE COASTS/VALLEYS, AND A 50-85% CHANCE OF AT  
LEAST 2" ON THE COASTAL MOUNTAIN SLOPES. GIVEN HOW DEEP THE  
SATURATED LAYER IS, SPILLOVER INTO THE DESERTS SHOULD BE NO ISSUE,  
AND EVEN THE LOWER DESERTS HAVE A 35% CHANCE OF AT LEAST 0.50"  
(60-70% CHANCE OF AT LEAST 0.50" IN THE HIGH DESERT). DETAILS ARE  
LIKELY TO CHANGE, BUT AT THIS POINT THIS WILL BE THE LARGEST  
PRECIPITATION EVENT OF THE SEASON BY FAR, THOUGH NOT NEARLY ENOUGH  
TO PULL US OUT OF OUR WATER YEAR DEFICIT.  
 
AS FAR AS SNOW LEVELS, THEY WILL START OUT NEAR 5000-6000 FT  
WEDNESDAY MORNING, CLIMBING TO OVER 7500 FT DURING THE DAY  
THURSDAY IN WARM AIR ADVECTION AHEAD OF THE TROUGH BEFORE FALLING  
TO AROUND 5500 FT FRIDAY AFTERNOON AND DOWN TO AROUND 5000 FT  
FRIDAY EVENING AS PRECIPITATION TAPERS OFF.  
 

 
   
AVIATION
 
 
081000Z...COAST/VALLEYS...PATCHY LOW CLOUDS COVER MOST OF THE  
COASTAL BASIN THIS MORNING. BASES ARE AT 2500-3500 FT MSL, AND WILL  
CONTINUE TO RISE SLIGHTLY THROUGH LATE THIS MORNING. CLOUDS WILL  
PARTIALLY SCATTER OUT IN AREAS OVERNIGHT, WITH GREATER CLEARING 15-  
17Z. WIDESPREAD LOW CLOUDS ARE NOT EXPECTED TO RETURN THIS EVENING,  
WITH A 10% OR LESS CHANCE FOR LOW-LEVEL CIGS AT ANY SITE, BUT HIGH-  
LEVEL CLOUDS AT 15000-25000 FT MSL WILL CONTINUE TO MOVE OVER THE  
REGION TODAY AND TONIGHT.  
 
MOUNTAINS/DESERTS...HIGH CLOUDS 15000-25000 FT MSL AND VFR  
CONDITIONS TODAY AND TONIGHT.  
 

 
   
MARINE
 
 
NO HAZARDOUS WEATHER IS EXPECTED THROUGH EARLY TUESDAY. NORTHWEST  
WINDS WILL STRENGTHEN TUESDAY AFTERNOON.  
 

 
   
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  
AVIATION/MARINE...CSP  
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab CA Page Main Text Page