RNOHMDRSA (02/09/10 0923)


AGUS76 KRSA 091723
HMDRSA

HYDROMETEOROLOGICAL DISCUSSION
NATIONAL WEATHER SERVICE / CALIFORNIA NEVADA RFC / SACRAMENTO CA
930 AM PST TUE FEB 9 2010

...AN UPPER-LEVEL LOW WILL CONTINUE TO BRING PRECIP TO CENTRAL AND 
SRN PORTIONS OF THE FORECAST AREA TODAY...

.24 HOUR PRECIPITATION TOTALS (ENDING FEB 9 AT 400 AM PST)...

AN INITIAL LINE OF MOISTURE MOVED ONSHORE ACROSS THE SAN FRANCISCO 
BAY AREA INLAND OVER THE SACRAMENTO VALLEY AND NORTHERN SIERRA LAST 
EVENING. OVERNIGHT...AN UPPER LOW DIVING SOUTH-SOUTHEAST ALONG THE 
NORTHERN CALIFORNIA COAST BROUGHT PRECIP DOWN TO THE CENTRAL COAST 
AND INLAND OVER THE SHASTA DRAINAGE SOUTH TH THE SOUTHERN SIERRA.

GREATEST TOTALS WERE RECORDED OVER THE NORTHERN SIERRA BETWEEN THE 
FEATHER RIVER BASIN AND AMERICAN RIVER BASIN WITH 0.25- TO 0.50-INCH 
(LOCAL 0.75-INCH). 

TOTALS NEAR 0.25-INCH (OR SLIGHTLY HEAVIER) WERE RECORDED OVER THE 
SHASTA DRAINAGE AND COASTAL MOUNTAINS FROM WESTERN TEHAMA COUNTY 
SOUTH TO THE BIG SUR COAST.

INLAND OVER THE SACRAMENTO VALLEY AMOUNTS WERE GENERALLY NEAR 
0.10-INCH...WHILE OVER THE NORTHERN SAN JOAQUIN VALLEY A FEW 
HUNDREDTHS WERE RECORDED. A COUPLE HUNDREDTHS TO 0.10-INCH WERE ALSO 
OBSERVED OVER THE SOUTHERN SIERRA.

.METEOROLOGICAL CONDITIONS...

AN UPPER-LEVEL LOW OFF THE CA COAST WILL BRING PERIODS OF RAIN AND 
SHOWERS TO ALL BUT THE FAR NRN AREAS OF CA TODAY AND CNTRL AND SRN 
NV AS WELL.  RADAR AND SATELLITE IMAGERY SHOW THE CENTER OF THE 
UPPER LOW IS JUST OFFSHORE OF SF BAY CURRENTLY...AND MODELS TAKE THE 
LOW PARALLEL TO THE COAST THROUGH THE DAY...KEEPING IT GENERALLY 
OFFSHORE AND PLACING IT OFF THE SRN CA COAST BY THIS EVENING.  THUS 
THE FOCUS OF PRECIP WILL GRADUALLY SHIFT SWD INTO SRN CA THROUGH THE 
MORNING HOURS.  THE CLOSE PROXIMITY OF THE UPPER LOW COMBINED WITH 
SWLY WINDS IN THE LOW LEVELS WILL PROVIDE HEAVIER TOTALS ALONG THE 
TRANSVERSE RANGES LATER THIS MORNING AND THIS AFTERNOON.  PRECIP 
WILL TAPER OFF ACROSS SRN CA AND SRN NV BY WED MORNING AS THE UPPER 
LOW MOVES SOUTH AND EAST AWAY FROM THE REGION.

BY WED NIGHT...LIGHT PRECIP WILL SPREAD INTO NW CA ASSOCIATED WITH 
ISENTROPIC LIFT AND WARM ADVECTION.  MODELS KEEP THE LIGHT PRECIP 
GOING THROUGH THE DAY THUR BEFORE RAIN RATES BEGIN TO PICK UP THUR  
AFTERNOON IN ADVANCE OF A COLD FRONT.  ANOTHER FRONT SWINGS THROUGH 
ON FRI AFTERNOON TO KEEP PRECIP GOING FOR MAINLY THE NRN THIRD OF CA 
INTO SRN OREGON.  RIDGING BUILDS THIS WEEKEND TO PROVIDE A DRYING 
TREND FOR THE NORTHERN PORTION OF THE REGION.


DAY 1 QPF (TUE 09/12Z TO WED 10/12Z): 0.6-0.8" NEAR THE SRN CA COAST 
WITH 0.75-1.25" IN THE HIGHER TERRAIN...WITH SLIGHTLY LOWER AMOUNTS 
ON THE WRN END OF THE TRANSVERSE RANGES. AROUND 0.33-0.6" SANTA 
LUCIA RANGE AND SANTA CRUZ MTNS. AROUND 0.25" OR LESS FROM THE 
RUSSIAN/NAPA BASIN TO THE EEL BASIN AND DRY FURTHER NORTH ALONG THE 
COAST. 0.25-0.4" AMOUNTS THROUGH THE CA CENTRAL VALLEY AND AROUND 
0.1" OR LESS IN THE LAKE SHASTA REGION. GENERALLY 0.4-0.8" IN THE 
SRN SIERRAS AND 0.15-0.33" CNTRL AND NRN SIERRAS. GENERALLY LESS 
THAN 0.1" EAST SLOPES OF THE SIERRAS...NE CA...AND CNTRL NV. 0.25- 
0.5" ON AVERAGE IN SRN NV AND ADJACENT AREAS OF SERN CA..TRAILING 
OFF TO LESS THAN 0.1" INTO FAR SE CA.

DAY 2 QPF (WED 10/12Z TO THU 11/12Z): 0.1" OR LESS SRN AND SERN CA 
AS WELL AS SRN NV. ALSO 0.1" OR LESS NWRN AND FAR NRN CA AND SRN 
OREGON EXCEPT 0.1-0.25" SMITH BASIN.

DAY 3 QPF (THU 11/12Z TO FRI 12/12Z): GENERAL 0.5-1" AMOUNTS IN THE 
SMITH AND EEL BASINS AS WELL AS IN THE LAKE SHASTA REGION. 0.25-0.5" 
AMOUNTS MENDOCINO AND TRINITY COUNTIES TRAILING OFF TO A FEW 
HUNDREDTHS INTO THE RUSSIAN/NAPA BASINS.  IN THE CENTRAL VALLEY... 
LESS THAN 0.1" FROM RBL SOUTH TO KMYV AND UP TO AROUND 0.33" FURTHER 
NORTH. 0.25-0.4" BELOW LAKE SHASTA AND 0.5-0.9" ABOVE THE LAKE.  
GENERALLY 0.15-0.33" IN FAR NRN CA AND SRN OREGON. LIGHT AMOUNTS 
0.1" OR LESS FROM I-80 NORTHWARD IN THE SIERRAS AND NE CA EXCEPT UP 
TO AROUND 0.33" AND LOCALLY HIGHER IN THE FAR NRN SIERRAS.


.HYDROLOGICAL CONDITIONS...

PRECIPITATION FORECAST FOR TODAY IS EXPECTED TO PRODUCE ONLY MINOR 
RISES TO RIVER FORECAST POINTS IN CALIFORNIAS CENTRAL VALLEY 
REGION... THE RUSSIAN/NAPA... CENTRAL COAST AND SOUTH COASTAL 
BASINS.  

MINOR RISES TO SOME NORTHERN CALIFORNIA RIVERS AND STREAMS ARE 
EXPECTED FROM PRECIPITATION FORECAST FOR DAY 3.

OVERFLOW INTO THE SUTTER BYPASS AT TISDALE WEIR IS FORECAST TO END 
THIS EVENING.

ALL OTHER RIVER FORECAST POINTS ARE EXPECTED TO REMAIN BELOW MONITOR 
LEVELS DURING THE NEXT SEVERAL DAYS.


MORE INFORMATION ON THE CNRFC WEBSITE AT HTTP://WWW.CNRFC.NOAA.GOV

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