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Weather Alert Detail

  • Hydrologic Outlook for East Bay Hills and the Diablo Range County, California
  • Hydrologic Outlook issued March 02 at 12:42PM PST until March 08 at 3:00PM PST by NWS
  • Effective: Wednesday, March 2, 2016 at 12:42 p.m.
  • Expires: Tuesday, March 8, 2016 at 3 p.m.
  • SERIES OF STORM SYSTEMS TO ARRIVE IN CALIFORNIA
    BEGINNING AS EARLY AS THURSDAY, MARCH 3, THE BAY AREA`S PREVIOUS
    MID-WINTER DRY SPELL WILL MAKE AN ABOUT-FACE INTO A PREDOMINANTLY
    WET PATTERN. RAINFALL ON THURSDAY WILL BE LIGHT, WITH ACCUMULATION
    GENERALLY WELL LESS THAN AN INCH AND MOSTLY CONCENTRATED FROM THE
    SANTA CRUZ MOUNTAINS NORTHWARD. BY FRIDAY MORNING ONLY THE SANTA
    CRUZ MOUNTAIN AND THE COASTAL MOUNTAINS OF SONOMA COUNTY MAY
    RECEIVE RAINFALL IN EXCESS OF AN INCH. AGAIN, LIGHT RAIN IS
    EXPECTED THROUGH FRIDAY, BUT RAINFALL INTENSITY IS EXPECTED TO
    INCREASE IN THE OVERNIGHT HOURS. TOTALS FOR THE 24-HOUR PERIOD
    BEGINNING FRIDAY AT 4AM LOCAL EXTENDING TO SATURDAY 4AM ARE LIKELY
    TO REACH 1-2 INCHES IN COASTAL MOUNTAINS THROUGHOUT THE SERVICE
    AREA, INCLUDING THE SANTA LUCIAS IN MONTEREY COUNTY. A
    CONTINUATION OF INTENSE RAIN WILL FOLLOW, WITH SEVERAL MORE INCHES
    FALLING OVER SATURDAY AND SUNDAY, AGAIN CONCENTRATED IN COASTAL
    RANGES. SIX-DAY TOTALS, EXTENDING FROM WEDNESDAY MARCH 2 THROUGH
    EARLY TUESDAY MORNING, SHOULD YIELD 4-7 INCHES IN COASTAL
    MOUNTAINS AND 1-3 INCHES IN VALLEY FLOORS AND INLAND AREAS.
    UNCERTAINTY REMAINS ON THE SPECIFICS OF WEATHER PATTERNS FOR NEXT
    WEEK. ALTHOUGH MOST MODELS AND FORECASTER INPUT SUGGEST CONTINUED
    WET WEATHER THROUGH NEXT WEEK, THE EXACT TIMING, LOCATION, AND
    AMOUNT REMAIN UNCERTAIN. WITH WET WEATHER EXPECTED FOR NEXT WEEK,
    FOLLOWING SEVERAL INCHES OF RAIN OVER THE WEEKEND, RAIN WILL
    LIKELY BE FALLING ON NEAR-SATURATED TO SATURATED SOILS. THUS
    WATERSHEDS WILL BE PRIMED TO QUICKLY CONVERT RAIN INTO RUNOFF AND
    WILL ALSO HAVE THE POTENTIAL TO GENERATE DEBRIS FLOWS AND
    LANDSLIDES IN SATURATED AREAS WHERE RAINFALL RATES EXCEED 1-INCH
    PER HOUR.
    IMPACTS ASSOCIATED WITH THE RAINFALL EXTENDING THROUGH THE WEEKEND
    WILL LIKELY BE LIMITED TO URBAN FLOODING IN AREAS WHERE STORM
    DRAINS BECOME CLOGGED OR OVERWHELMED BY RUNOFF DURING INTENSE
    BURSTS OF RAIN. LOW LYING AGRICULTURAL AREAS MAY ALSO EXPERIENCE
    PONDING AND RUNOFF MAY ENTER ROADWAYS ADJACENT TO POORLY DRAINED
    FIELDS. THE EXTENT TO WHICH CREEKS MAY JUMP THEIR BANKS WILL
    LARGELY DEPEND ON THE INTENSITY OF RAINFALL: INTENSE BURSTS
    SEPARATED BY LIGHT RAIN OR REPRIEVES MAY PROVIDE INITIALLY DRY
    WATERSHEDS TO INFILTRATE RAINFALL AND CONTAIN RUNOFF WITHIN
    CHANNELS. PROTRACTED INTENSE RAIN, WHICH IS POSSIBLE (AND APPEARS
    LIKELY OVER THE WEEKEND), MAY CAUSE SOME FAST RESPONDING BASINS TO
    FLOOD. EXAMPLES OF THIS TYPE OF BEHAVIOR ARE LIKELY TO OCCUR IN
    VALLEY SETTINGS OF THE NORTH BAY, PARTICULARLY IN THE PETALUMA
    BASIN, AND THE VALLEY FORD, BODEGA, AND BLOOMFIELD AREAS FED BY
    STEMPLE CREEK, SALMON CREEK, AND THE ESTERO AMERICANO. THE LOWER
    LAGUNA DE SANTA ROSA MAY ALSO EXPERIENCE ROUTINE FLOODING AND
    DRAINAGE IMPACTS. QUICK URBAN DRAINAGE IN THE SANTA CLARA VALLEY
    CREEKS THAT ORIGINATE IN THE SANTA CRUZ MOUNTAINS MAY ALSO
    EXPERIENCE PROBLEMS. NOTABLY, WE WILL BE WATCHING THE LOS GATOS-
    GUADALUPE BASIN CLOSELY, AS WELL AS UPPER LLAGAS, SARATOGA,
    STEVENS, PERMANENTE, AND OTHER INTERVENING LOCAL DRAINAGES.
    HOWEVER, MOST CREEKS AND RIVERS IN THE SERVICE AREA WILL REMAIN
    BELOW FLOOD LEVELS, BASED ON THE EXPECTED RAINFALL RATES DESCRIBED
    HERE. SHOULD RAINFALL FORECASTS INCREASE, THIS STORY MAY CHANGE,
    SO PLEASE STAY TUNED TO UPDATES FROM THE SAN FRANCISCO BAY AREA
    NWS OFFICE.
    PLEASE STAY TUNED TO LOCAL MEDIA OUTLETS AND OUR OWN NWS SOCIAL
    MEDIA ACCOUNTS AND WEB PAGE FOR ADDITIONAL AND UPDATED INFORMATION
    PRECEDING AND DURING THE STORM. AND PLEASE STAY SAFE!