822  
AGUS76 KRSA 112048  
HMDRSA  
 
HYDROMETEOROLOGICAL DISCUSSION  
NATIONAL WEATHER SERVICE / CALIFORNIA NEVADA RFC / SACRAMENTO CA  
1250 PM PST TUE FEB 11 2025  
   
..WEAK LOW PRESSURE AFFECTS CENTRAL/SOUTHERN CA COASTAL AREAS WED
 
   
..MODERATE/HEAVY PRECIP ESPECIALLY I-80 SOUTH LATE WED INTO FRI
 
 
   
METEOROLOGICAL CONDITIONS (SHORT TERM: TUE PM - FRI AM)
 
 
STILL ANTICIPATING A WEAK AREA OF LOW PRESSURE TO DROP SOUTHEAST  
FROM ITS CURRENT LOCATION JUST ABOVE 40N AND OUTSIDE OF 130W TO  
REACH NEAR THE CENTRAL/SOUTHERN CA COAST ON WEDNESDAY WITH MAINLY  
LIGHT TO LOCALLY MODERATE AMOUNTS BETWEEN THE SF BAY AREA SOUTHWARD  
TO THE CA/MX BORDER (0.10- TO 0.33-INCH LOCAL TO 0.50-INCH). OVERALL  
THINKING WITH THIS SYSTEM HASN/T CHANGED MUCH WITH ADJUSTMENTS  
PRIMARILY AROUND A FEW HUNDREDTHS OF AN INCH TO 0.10-INCH.  
 
THE MORE IMPACTFUL SYSTEM IS STILL ANTICIPATED FOR LATE WEDNESDAY  
THROUGH THURSDAY WITH PRECIP TAPERING OFF ON FRIDAY...AS A S/WV TROF  
SPINS UP WITH A DEEPENING SFC LOW (BETWEEN 980- AND 985-MB) AND  
MOVES EAST ALONG 40N AND TAPS INTO A LONG FETCH OF ELEVATED MOISTURE  
BACK TO THE WEST-CENTRAL PACIFIC. THE MOISTURE PLUME IS STILL  
EXPECTED TO INTERSECT THE COAST NEAR THE SF BAY AREA AND THEN ADVECT  
INLAND AND PUSH SOUTHWARD AS THE S/WV TROF APPROACHES THE COAST.  
MAIN CHANGES TO THE AFTERNOON FORECAST WERE TO INCREASE AMOUNTS  
SLIGHTLY ALONG THE NORTH COAST AS THE S/WV TROF APPROACHES AND COLD  
FRONT PASSES ACROSS THE AREA. ALSO...INCREASES WERE MADE TO THE  
SOUTHERN SIERRA...WHERE MODELS ARE HINTING AT A HEAVY 12-HOUR PERIOD  
OF PRECIP BETWEEN 12Z THURSDAY AND 00Z FRIDAY. THESE TWO INCREASES  
WERE IN THE RANGE OF 0.10- TO 0.33-INCH. OTHERWISE THE FORECAST IS  
GENERALLY ON TRACK WITH THE GREATEST AMOUNTS FROM I-80 AND POINTS  
SOUTH. STORM TOTALS ALONG COASTAL LOCATIONS WILL BE IN THE RANGE OF  
1.00- TO 3.00-INCHES EXCEPT 3.00- TO 7.00-INCHES FOR PORTIONS OF THE  
SANTA CRUZ AND SANTA LUCIA MOUNTAINS...AND THEN PAST POINT  
CONCEPTION OVER THE SOUTH FACING SLOPES OF THE TRANSVERSE RANGES  
BETWEEN SANTA BARBARA AND SOUTHWEST SAN BERNARDINO COUNTIES. INLAND  
OVER THE SIERRA...WIDESPREAD AMOUNTS FROM 3.00- TO 7.00-INCHES ARE  
LIKELY WITH THE HEAVIEST BETWEEN THE MERCED AND KERN RIVER BASINS.  
CENTRAL VALLEY LOCATIONS SHOULD REMAIN BETWEEN 1.00- AND 2.00-INCHES.  
 
FREEZING LEVELS ARE CURRENTLY FROM 500- TO 1500-FEET ACROSS FAR  
NORTHERN AREAS...WITH A BROAD AREA OF 2000- TO 5000-FEET DOWN ACROSS  
CENTRAL AREAS...WITH 7000- TO 8000-FEET OVER SOUTHERN AREAS. THESE  
WILL BUMP UP SLIGHTLY WITH THE ARRIVAL OF THE MORE IMPACTFUL  
SYSTEM...RISING TO 4500-FEET NORTH TO 8500-FEET SOUTH WITH A BROAD  
AREA BETWEEN 5000- AND 7000-FEET FROM NORTH-TO-SOUTH.  
 
   
METEOROLOGICAL CONDITIONS (LONG TERM: FRI AM - MON AM)
 
 
NO SIGNIFICANT CHANGES TO THE AFTERNOON FORECAST. SLIGHT DECREASES  
(<0.10 INCHES) ALONG THE SIERRA AND SOUTHERN CALFIORNIA COAST AS  
SOME GUIDANCE SUGGESTS A QUICKER DISSIPATION OF THE SYSTEM FRIDAY  
MORNING. LARGER, BUT STILL MODEST DECREASES (0.10 INCHES) OVER THE  
NORTH COAST WITH THE NEXT SYSTEM SLIDING DOWN THE COAST ON SUNDAY.  
 
FRIDAY WILL SEE LIGHTER PRECIPITATION ACCUMULATIONS AS THE WEAKENING  
SURFACE LOW AND ATMOSPHERIC RIVER BEGIN SHIFTING INLAND OVER  
CALIFORNIA. UNCERTAINTY IN THE TIMING, PLACEMENT, AND TRACK OF THE  
LOW MOVING ONSHORE OVER THE PACIFIC NORTHWEST/NORTHERN CALIFORNIA AS  
WELL AS THE SPEED THE MOISTURE PLUME DEPARTS SOUTHERN CALIFORNIA IS  
LEADING TO SOME MODEL UNCERTAINTY IN AMOUNTS ACROSS THE STATE. EVEN  
WITH SOME UNCERTAINTY, ACCUMULATIONS ARE GENERALLY ON THE LIGHTER  
END FOR FRIDAY (COMPARED TO THE SHORT TERM WINDOW) WITH UP TO 0.75  
INCHES OVER THE SIERRA, ~0.3 INCHES OVER THE NORTH COAST, AND 0.3-  
0.6 INCHES FOR THE EASTERN TRANSVERSE AND LAGUNA MOUNTAINS IN  
SOUTHERN CALIFORNIA. COLD AIR ALOFT COMBINED WITH THE LIFT SUPPORT  
FROM THE LOW COULD LEAD TO LINGERING THUNDERSTORM ACTIVITY ACROSS  
THE REGION AND, THEREFORE, LOCALLY HEAVIER PRECIPITATION.  
 
SATURDAY MORNING INTO THE AFTERNOON WILL SEE A LULL IN PRECIPITATION  
BEFORE ANOTHER WEAKER SYSTEM SLIDES DOWN THE COAST FROM THE PACIFIC  
NORTHWEST TO FAR NORTHWESTERN CALIFORNIA SATURDAY EVENING INTO  
SUNDAY. GUIDANCE CURRENTLY DIFFERS QUITE A BIT ON HOW QUICKLY THE  
MOISTURE PLUME WILL DISSIPATE WITH THE GFS NOT BRINGING ANY IVT >250  
UNITS TO CALIFORNIA AND THE EC SPREADING AR CONDITIONS AS FAR SOUTH  
AS SONOMA COUNTY. SLIGHT CONVERGENCE BETWEEN THE MODELS HAS LED TO  
MINOR DECREASES IN ACCUMULATIONS ACROSS THE NORTH COAST OF UP TO  
0.13 INCHES.  
 
FREEZING LEVELS WILL START THE PERIOD RANGING FROM <4K FEET TO 7.5K  
FEET NORTH-SOUTH UNDER THE UPPER TROUGH BEFORE RISING SATURDAY TO 8K-  
12.5K FEET. ANOTHER LOWERING ON SUNDAY INTO MONDAY TO 4.5K-11.5K  
NORTH-SOUTH WITH ADDITIONAL TROUGH ACTIVITY.  
 
QPF GRAPHICS ARE AVAILABLE AT WWW.CNRFC.NOAA.GOV/QPF.PHP  
 
KOZLOWSKI/CH  
 

 
 
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