MESOSCALE PRECIPITATION DISCUSSION 0086
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
302 PM EDT SUN MAR 13 2016
 
AREAS AFFECTED...NORTHERN AND CENTRAL CA 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 132000Z - 140100Z
 
SUMMARY...A CONTINUING PERIOD OF MODERATE TO HEAVY RAINFALL...WITH
HOURLY RAINFALL RATES NEAR 0.50 INCHES...COULD RESULT IN A
LOCALIZED FLASH FLOOD THREAT INTO EARLY EVENING.

DISCUSSION...DEEP MOISTURE ASSOCIATED WITH THE CURRENT ATMOSPHERIC
RIVER (WITH PRECIPITABLE WATER VALUES NEAR 1.20 INCHES WEST OF
SFO) CONTINUES ACROSS NORTHERN CA AHEAD OF A COLD FRONT ASSOCIATED
WITH DEEP LOW PRESSURE OFF THE PACIFIC NORTHWEST COAST. HOURLY
RAINFALL RATES HAVE AVERAGED BETWEEN 0.25 AND 0.50 INCHES (PER
KBHX RADAR AND THE MRMS PRECIPITATION RATE PRODUCT)...AND MESONET
OBSERVATIONS SUPPORT THAT RANGE.

THE NEXT 300 MB JET SEGMENT COMES ASHORE ACROSS NORTHERN CA DURING
THE LATE AFTERNOON HOURS. THE MOISTURE PLUME REMAINS APPROXIMATELY
THE SAME (AS THE LATEST HRRR/RAP SHOWED PRECIPITABLE WATER VALUES
NEAR 1.25 INCHES...WHICH BETWEEN TWO AND THREE STANDARD DEVIATIONS
ABOVE THE MEAN) AHEAD OF THE FRONT...WHICH COMES ASHORE BETWEEN
22Z-01Z (FROM NORTH TO SOUTH). 

THE STRONG MOISTURE FLUX ON A 35 KNOT LOW LEVEL FLOW CAN SUPPORT
HOURLY RAINFALL RATES NEAR 0.50 INCHES...AS STEEP MID LEVEL LAPSE
RATES CAN SUPPORT MARGINAL INSTABILITY (PER RAP MODEL SOUNDINGS).
THE LATEST HRRR/RAP/12Z WRF ARW ALL SUPPORT HOURLY RAINFALL RATES
BETWEEN 20Z AND 02Z...MAINLY ACROSS NORTHERNMOST CA. UPSLOPE FLOW
MAY ALSO CONTRIBUTE TO HOURLY RAINFALL RATES NEAR 0.50
INCHES...MAINLY ON SOUTHWEST FACING SLOPES. 

THE ADDITIONAL RAINFALL OVER SATURATED SOILS (AS MOST AREAS HAVE
SEEN RAINFALL AMOUNTS OF 300 TO 600 PERCENT OF NORMAL FOR THE PAST
WEEK) COULD RESULT IN LOCALIZED FLASH FLOODING...AS WELL AS
MUDSLIDES AND FLOODING OVER BURN SCARS.

HAYES

ATTN...WFO...EKA...MFR...MTR...STO...

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

LAT...LON   41872379 41812356 41712343 41562316 41522303 
            41522273 41552252 41572234 41582217 41612202 
            41572175 41422161 40932143 40682140 40382125 
            39892097 39672088 39582085 39422086 39292083 
            39122078 38942070 38832065 38712058 38622053 
            38502043 38362041 38212048 38152066 38262079 
            38462091 38752112 38872099 39092111 39252125 
            39462152 39662168 39812171 39922169 40032166 
            40472176 40662173 40742227 40742260 40742307 
            40692320 40482304 40372298 40172287 39592275 
            39372276 39132272 38922253 38822238 38452209 
            38272195 37842178 37582175 37322178 37392216 
            37912265 38272291 38562328 40092398 40182395 
            40312395 40472396 40702395 40982395 41182397 
            41372402 41562409 41682406 41772404 41832396