MESOSCALE PRECIPITATION DISCUSSION 0062
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
128 PM EST MON FEB 20 2017

AREAS AFFECTED...AREAS AFFECTED...CA COAST...CA CENTRAL
VALLEY...SIERRA-NEVADA FOOTHILLS

CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE

VALID 201827Z - 210227Z

SUMMARY...ATMOSPHERIC-RIVER DRIVEN MODERATE TO HEAVY RAINFALL
CONTINUES ACROSS THE CENTRAL CALIFORNIA COAST INTO THE SIERRA
NEVADA FOOTHILLS THROUGH 0230Z THIS EVENING.

DISCUSSION...LATEST BLENDED-TPW DATA CONTINUES TO SHOW A SURGE OF
ATMOSPHERIC RIVER MOISTURE BRINGING HEAVY RAINFALL ACROSS CENTRAL
CA FOR THIS AFTERNOON THROUGH THIS EVENING. MODEL GUIDANCE
INDICATES A STRENGTHENING OF THE LOW-LEVEL JET OVER THE NEXT FEW
HOURS...ALONG AND AHEAD OF A COLD FRONT ASSOCIATED WITH LOW
PRESSURE OVER WESTERN OR. LLJ REACHING 40 TO 50 KTS THROUGH
00Z...IN TANDEM WITH THE ARRIVAL OF A STRONG UPPER LEVEL JET
STREAK THAT IS CURRENTLY OVER 140 KTS AT 250 MB SOUTHWEST OF THE
DEEPENING LOW CENTER...WILL BRING HEAVY RAINS TO THE CENTRAL CA
COASTAL RANGE THROUGH 00Z...WITH HEAVIER RAINS THEREAFTER EXPECTED
TO SET UP INLAND ACROSS THE SACRAMENTO VALLEY AND THE
SIERRA-NEVADA FOOTHILLS FROM 21Z THROUGH 02Z AND BEYOND.

ON AVERAGE...RAINFALL RATES OF AROUND 0.5 INCH/HR CAN BE EXPECTED
OVER THE CENTRAL CA COASTAL RANGES IN VICINITY OF SAN MATEO AND
ESPECIALLY SANTA CRUZ COUNTIES. HERE...GIVEN THE ORTHOGONAL
ORIENTATION OF THE LOW-LEVEL JET RELATIVE TO THE TERRAIN...THE AID
OF STRONG OROGRAPHICS IN IS EXPECTED TO GENERATE 0.75-1+ INCH/HR
RAINFALL RATES. FARTHER INLAND INTO THE FOOTHILLS OF THE
SIERRA-NEVADA BELOW SNOW LEVEL...0.50 TO 0.75 INCH/HR RAINFALL
RATES CONTINUE THROUGH 21-00Z...WITH ADDITIONAL DEVELOPMENT AFTER
00Z EXPECTED ALONG THE I-80 CORRIDOR FROM NEVADA TO PLACER AND EL
DORADO COUNTIES.

THESE RAINS ARE EXPECTED TO RESULT IN ADDITIONAL CONCERNS FOR
RUNOFF PROBLEMS AND AT LEAST ISOLATED FLASH FLOODING GIVEN THE
SATURATED SOIL CONDITIONS AND LOCALIZED BURN SCARS. DEBRIS FLOWS
AND MUDSLIDES WILL BE POSSIBLE. ADDITIONAL HEAVY RAINS WILL OCCUR
AFTER 00Z...SO STAY TUNED FOR MORE UPDATES.

MONTEFUSCO

ATTN...WFO...HNX...LOX...MTR...REV...STO...

ATTN...RFC...CNRFC...

LAT...LON   39772077 39372030 38972013 38701992 38471947
            38291930 37971910 37691901 37511910 37381928
            37311937 37281951 37742005 38032052 37952086
            37612125 37212125 37052137 36802139 36602133
            36372129 36152127 35802096 35522090 35922133
            36242172 36422191 36652205 37002220 37232234
            37312249 37642255 37852259 37972290 38152307
            38392294 38582263 38792236 39002189 39002189
            38812170 38682168 38702127 39212117 39742086