A potential for "up to 20 inches" in the wettest areas, starting Sunday night, January 17th:
Issued by The National Weather Service / San Francisco/Monterey, CA / 2:15 pm PST, Thu., Jan. 14, 2010
Special Weather Statement for North Bay Interior Valleys, CATHE LATEST FORECAST MODELS CONTINUE TO DEPICT A SERIES OF STORMS WILL MOVE IN FROM THE PACIFIC AND IMPACT CALIFORNIA NEXT WEEK
THE FIRST OF THE MORE SIGNIFICANT SYSTEMS IS FORECAST TO SPREAD RAIN INTO OUR AREA STARTING LATE ON SUNDAY AND CONTINUING THROUGH MONDAY AFTERNOON. THIS SYSTEM COULD PRODUCE UP TO 3 INCHES OF NEW RAINFALL FOR THE HIGHER ELEVATIONS AND 1-2 INCHES FOR THE VALLEYS.
AFTER A BRIEF BREAK ON MONDAY NIGHT THE NEXT IN THE SERIES IS EXPECTED TO SPREAD MORE RAIN INTO OUR AREA THROUGHOUT THE DAY TUESDAY AND INTO TUESDAY EVENING. AN ADDITIONAL 2-4 INCHES OF RAINFALL IS POSSIBLE ACROSS THE HIGHER ELEVATIONS WITH 1-2 INCHES FOR THE VALLEYS.
A SECOND BREAK IS EXPECTED TUESDAY NIGHT INTO WEDNESDAY MORNING BEFORE THE NEXT AND MOST POWERFUL SYSTEM OF THE WEEK APPROACHES DURING THE DAY WEDNESDAY. THIS SYSTEM COULD LINGER WEILL INTO THURSDAY. TOTALS FOR THIS SYSTEM COULD REACH 3-5 INCHES OR MORE FOR THE HIGHER ELEVATIONS AND 1-3 FOR THE VALLEYS. AS THE FRONT MOVES THROUGH SHOWERS COULD PERSIST WELL INTO FRIDAY. ALSO OF NOTE... A VERY POWERFUL JET STREAM IS FORECAST TO BE OVER CALIFORNIA BY THE MIDDLE OF THE WEEK WHILE A DEEP SURFACE LOW IS POSITIONED OFF THE WASHINGTON COAST. THIS HAS THE POTENTIAL TO PRODUCE VERY STRONG WINDS AND HIGH WIND WARNINGS MAY BE NEEDED.
BY THE END OF THE WEEK AHEAD... TOTAL RAINFALL COULD REACH 10-15 INCHES AT THE HIGHER ELEVATIONS AND THE POTENTIAL FOR UP TO 20 INCHES IN THE WETTEST LOCATIONS. IN THE VALLEYS... 4-8 INCHES.
Link:
http://www.weather.com/weather/alerts/localalerts/94559?phenomena=TSL&significance=S&areaid=CAZ506&office=KMTR&etn=e34183c2155103809ce1557cde984fefeb7af5b6That sounds like heavy-duty flooding.