Flood Potential Outlook
Issued by NWS San Francisco Bay Area, CA

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HYDROLOGIC OUTLOOK
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA
241 PM PST MON DEC 1 2014

...2ND STORM SYSTEM TO BRING MORE INTENSE RAINS TO SAN FRANCISCO BAY
AREA SOUTH TO MONTEREY COUNTY...

THE SECOND OF TWO STRONG PACIFIC STORMS IS SET TO HEAD OVER THE
GREATER MONTEREY AND SAN FRANCISCO BAY AREAS BEGINNING MONDAY
NIGHT AND EXTENDING INTO WEDNESDAY. THIS STORM SYSTEM FOLLOWS ON
THE HEELS OF THE SYSTEM THAT JUST DELIVERED 1 TO SEVERAL INCHES OF
RAIN TO THE GREATER BAY AREA OVER THE PAST FEW DAYS. THE FIRST
SYSTEM BROUGHT 3-4 INCHES IN THE SANTA CRUZ AND COASTAL NORTH BAY
MOUNTAINS, WHICH CREATED SLICK ROADS AND DOWNED SOME TREES AND
POWER LINES IN ISOLATED LOCATIONS. NO FLOODING WAS REPORTED,
ALTHOUGH SOILS ARE NOW WELL SATURATED AND STREAMS ARE STILL
EMPTYING THE RUNOFF FROM RECENT RAINS.

THE FORECAST FOR THIS SECOND STORM SYSTEM IS FOR GENEROUS
PRECIPITATION TO ARRIVE IN TWO MAIN EPISODES. THE FIRST EPISODE IS
PREDICTED TO BEGIN LATE MONDAY NIGHT AND CONTINUING THROUGH MIDDAY
TUESDAY, BRINGING PERIODS OF HEAVY PRECIP MAINLY FOCUSED ON THE
SANTA LUCIA AND SANTA CRUZ MOUNTAINS, WITH LIGHTER PRECIP
ELSEWHERE IN THE BAY AREA. THE SECOND EPISODE IS SLATED TO COME
ROUGHLY 24 HOURS LATER, FROM LATE TUESDAY NIGHT INTO WEDNESDAY,
BRINGING WIDELY SPREAD PRECIP THROUGOUT THE REGION. THE SECOND
EPISODE, UNLIKE THE FIRST, MAY BRING MORE EVENLY DISTRIBUTED
PRECIPATION TO THE REGION, WITH THE POTENTIAL FOR FOCUS ON THE
NORTH BAY COUNTIES RATHER THAN MONTEREY BAY AND SOUTH. THE END
RESULT OF BOTH EPISODES IS THAT PRECIP TOTALS FOR MONDAY NIGHT
THROUGH WEDNESDAY MORNING MAY REACH UPWARDS OF 5 INCHES IN THE
SANTA LUCIA AND SANTA CRUZ MOUNTAINS. RUGGED AREAS OF THE NORTH
BAY MAY RECEIVE 2 TO 4 INCHES, AND OTHER BAY AREA LOCATIONS WILL
GENERALLY GET ABOVE AN INCH OF RAIN.

IMPACTS:
NOTING THAT SOILS ARE MOIST AND THAT WINDS MAY BE HIGHER WITH THIS
SECOND SYSTEM, THE MOST LIKELY IMPACTS IN COASTAL MOUNTAINS WILL
BE DOWNED TREES AND POWER LINES, AS WELL AS DEBRIS FLOWS AND ROCK
FALLS IN STEEP SATURATED AREAS. WITH THE SANTA LUCIAS EXPECTED TO
RECEIVE THE HIGHEST RAIN RATES, DEBRIS FLOW ACTIVITY IN THE
PFEIFFER BURN SCAR AREA OF SYCAMORE CANYON MAY BE A REAL DANGER.
IN SOME AREAS, AND DEPENDING ON RAINFALL INTENSITY, SOME ROADWAYS
AND AGRICULTURAL AREAS MAY BECOME FLOODED, AND STORM DRAINS MAY
BECOME CLOGGED OR TEMPORARILY OVERWHELMED. IN GENERAL, CREEK AND
RIVER FLOODING IS UNLIKELY, BUT THERE MAY BE LOWLAND DRAINAGES
THAT BECOME OVERWHELMED FROM RUNOFF ARRIVING FROM UPSTREAM IN THE
HILLS, ESPECIALLY IF THE RUNOFF ARRIVES ON A HIGH TIDE. THESE
LOCATIONS COULD INCLUDE THE LOWER LAGUNA DE SANTA ROSA AND
SURROUNDING AREAS, LOWER SONOMA VALLEY NEAR SCHELLVILLE, VALLEY
FORD AND BLOOMFIELD ALONG THE ESTERO AMERICANO, FALLON AND TWO
ROCK IN THE VICINITY OF STEMPLE CREEK, AND PETALUMA. AGRICULTURAL
AREAS IN THE LOWER SALINAS AND PAJARO VALLEYS AND NEAR MOSS
LANDING MAY EXPERIENCE LOCALIZED PONDING AND DRAINAGE PROBLEMS IF
THE HEAVY RAIN EXPECTED IN THE SANTA LUCIAS EXTENDS CONTINUOUSLY
UP TO THE SANTA CRUZ MOUNTAINS. OTHER URBAN CENTERS IN NORTHERN
MONTEREY COUNTY MAY EXPERIENCE NUISANCE FLOODING WITH THE FIRST
EPISODE OF RAIN.

BE SAFE, AND EXERCISE CAUTION, PARTICULARLY IN URBAN AREAS WHERE
PONDING AND DRAINAGE PROBLEMS DEVELOP. STAY TUNED TO LOCAL MEDIA
OUTLETS, WEATHER RADIO, NATIONAL WEATHER SERVICE WEB RESOURCES,
AND SOCIAL MEDIA. HEED INSTRUCTIONS AND WARNINGS DELIVERED BY
LOCAL EMERGENCY MANAGEMENT OFFICIALS.

WWW.WEATHER.GOV/SANFRANCISCO

WWW.FACEBOOK.COM/NWSBAYAREA

TWITTER.COM/NWSBAYAREA
@NWSBAYAREA

WWW.YOUTUBE.COM/NWSBAYAREA

$$

STRUDLEY





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