655  
AGUS76 KRSA 211505  
HMDRSA  
 
HYDROMETEOROLOGICAL DISCUSSION  
NATIONAL WEATHER SERVICE / CALIFORNIA NEVADA RFC / SACRAMENTO CA  
705 AM PST SAT DEC 21 2024  
   
..SERIES OF SYSTEMS TO IMPACT THE REGION THROUGH THE WEEK AHEAD  
 
   
METEOROLOGICAL CONDITIONS (SAT AM - FRI AM)  
 
THE FIRST OF A SERIES OF DISTURBANCES AFFECTING THE WEST COAST IS  
MOVING FROM SOUTHWEST TO NORTHEAST JUST OFF THE NORTHERN CA COAST  
THIS MORNING...ON ITS WAY TOWARD THE PACIFIC NORTHWEST LATER THIS  
AFTERNOON. PRECIP ASSOCIATED WITH THE COLD FRONT AND MOISTURE PLUME  
ENTRAINED AHEAD OF THE BOUNDARY IS CURRENTLY IMPACTING THE NORTHERN  
CA COASTAL MOUNTAINS...SPREADING INLAND ACROSS THE SHASTA LAKE  
DRAINAGE AREA AND SACRAMENTO VALLEY. AUTOMATED PRECIP GAUGES SHOW  
AREAS FROM THE EEL RIVER BASIN NORTHWARD TO THE CA/OR BORDER WITH  
THE BEST AMOUNTS SO FAR...GENERALLY FROM 0.25- TO 0.50-INCH. THROUGH  
THE REST OF TODAY...PRECIP WILL CONTINUE TO MOVE INLAND TOWARD THE  
NORTHERN SIERRA AND SOUTHWARD TO THE I-80 CORRIDOR BEFORE STARTING  
TO TAPER OFF AS THE SFC COLD FRONT BECOMES DIVORCED FROM THE BETTER  
MID-LEVEL FORCING TO THE NORTH. FREEZING LEVELS WILL RANGE FROM  
5500-FEET OR SO NEAR THE CA/OR BORDER...AND 8000- TO 9500-FEET ALONG  
THE I-80 CORRIDOR.  
 
SOME LIGHT PRECIP MAY LINGER THROUGH THE EVENING AND OVERNIGHT UNDER  
MOIST ONSHORE FLOW NEAR THE VICINITY OF THE WEAKENED FRONTAL  
BOUNDARY FROM THE SF BAY AREA INLAND ACROSS THE CENTRAL SIERRA AND  
PORTIONS OF NORTHWEST NV. THIS IS AHEAD OF THE NEXT S/WV TROF TO  
IMPACT THE REGION ON LATER SUNDAY INTO EARLY MONDAY. THE TRAJECTORY  
OF THE MID-LEVEL SYSTEM WILL MOVE WEST-SOUTHWEST TO EAST-NORTHEAST  
MAINLY ACROSS THE PACIFIC NORTHWEST...CLIPPING NORTHERN CA. AMOUNTS  
WITH THIS QUICK MOVING SYSTEM WILL BE LIMITED...EVEN THOUGH  
AVAILABLE MOISTURE IS DECENT...GIVEN THE DURATION OF THE PRECIP.  
BEST AMOUNTS WILL REMAIN OVER THE HIGHER TERRAIN FROM ABOUT I-80  
NORTHWARD WITH 0.25- TO 0.75-INCH. LOWER ELEVATIONS WILL GENERALLY  
RANGE FROM 0.10- TO 0.33-INCH. FREEZING LEVELS WILL REMAIN ELEVATED  
WITH THIS SYSTEM AS WELL...FROM 6000- TO 7500-FEET NEAR THE CA/OR  
BORDER TO 8000- TO 9500-FEET ALONG THE I-80 CORRIDOR.  
 
THE THIRD S/WV TROF MAKING ITS WAY TOWARD THE WEST COAST LOOKS TO BE  
A BIT MORE IMPRESSIVE...SHARPENING A AND ELONGATING BEFORE CROSSING  
THE COAST. LOOK FOR PRECIP TO SPREAD ACROSS THE REGION FROM  
NORTHWEST TO SOUTHEAST STARTING MONDAY AFTERNOON AND THEN LINGERING  
THROUGH THE EARLY EVENING HOURS ON TUESDAY. ALTHOUGH NORTHERN CA  
WILL SEE THE HIGHEST TOTALS FROM THIS SYSTEM...CENTRAL CA WILL SEE  
WIDESPREAD MODERATE AMOUNTS...WHILE EVEN SOUTHERN CA IS EXPECTED TO  
PICK UP SOME MAINLY LIGHT PRECIP. SOME TIMING AND STRENGTH OF THE  
SYSTEM DIFFERENCES AMONGST THE 21/00Z MODELS...BUT THIS FAR OUT THE  
GENERAL PATTERN IS HANDLED WELL ENOUGH TO HAVE MEDIUM CONFIDENCE IN  
OVERALL PRECIP TOTALS. LOOK FOR THE HIGHER TERRAIN OF NORTHERN CA TO  
RANGE FROM 1.00- TO 3.00-INCHES WITH A FEW LOCALIZED HIGHER AMOUNTS  
FOR THE SMITH RIVER BASIN AND KING RANGE. SACRAMENTO VALLEY  
LOCATIONS WILL SEE CLOSE TO 1.00-INCH SOUTH NEAR SACRAMENTO TO  
ALMOST 2.00-INCHES AROUND THE REDDING AREA. CENTRAL CA WILL ADD UP  
0.75- TO 1.50-INCHES ACROSS THE HIGHER TERRAIN WITH THE SAN JOAQUIN  
VALLEY RANGING FROM 0.10-INCH OR SO NEAR BAKERSFIELD TO 0.75-INCH  
AROUND STOCKTON. AREAS SOUTH OF POINT CONCEPTION WILL GENERALLY BE  
NEAR OR LESS THAN 0.10-INCH. FOR NV...TOTALS WILL BE BEST OVER THE  
NORTHERN HALF OF THE STATE WITH 0.10-INCH FOR LOWER ELEVATIONS AND  
0.50-INCH OVER FAVORABLE TERRAIN...WHILE THE SOUTHERN HALF OF THE  
STATE WILL GENERALLY BE NEAR OR LESS THAN 0.10-INCH EVERYWHERE.  
FREEZING LEVELS WILL START REASONABLY ELEVATED FROM NEAR 8000-FEET  
TO AS HIGH AS 13000-FEET (NORTHEAST TO SOUTHWEST GRADIENT). BEHIND  
THE FRONTAL BOUNDARY...THESE WILL FALL AS THE CORE OF THE S/WV TROF  
MOVES OVERHEAD...DOWN TO 3500- TO 4500-FEET NORTH...WITH 5500- TO  
7500-FEET CENTRAL...AND ABOVE 8000-FEET TO 12500-FEET SOUTH.  
 
AFTER THIS SYSTEM EXITS THE REGION TO THE EAST EARLY ON CHRISTMAS  
DAY...CONDITIONS WILL BE PRIMARILY DRY FOR THE HOLIDAY. THE NEXT  
DISTURBANCE WILL ARRIVE ON THURSDAY WITH ANOTHER ROUND OF PRECIP  
MAINLY FOCUSED ACROSS NORTHERN CA AND TAPERING OFF ACROSS CENTRAL  
CA.  
 
QPF GRAPHICS ARE AVAILABLE AT WWW.CNRFC.NOAA.GOV/QPF.PHP  
 
KOZLOWSKI  
 
 
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