MESOSCALE PRECIPITATION DISCUSSION 0043
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
758 PM EST SAT MAR 05 2016
 
AREAS AFFECTED...NRN CA...SRN OR 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 060058Z - 060428Z
 
SUMMARY...BROAD SCALE CONDITIONS WILL FAVOR INCREASED RAIN RATES
THROUGHOUT NORTHERN CALIFORNIA...WHILE TRAINING CONVECTION IN THE
CENTRAL VALLEY MAY LEAD TO UNUSUALLY HEAVY RAINFALL AND FLASH
FLOODING.

DISCUSSION...ALL OF NORTHERN CALIFORNIA AND SOUTHWEST OREGON WAS
AT SOME RISK OF HEAVY RAINFALL AND LOCAL RUNOFF PROBLEMS...IF NOT
FLASH FLOODING. THIS...AS A WIDE ATMOSPHERIC RIVER BECOMES MORE
SOUTH-NORTH ORIENTED UPON BEING SWEPT INLAND BY AN APPROACHING
COLD FRONT. THE 22Z HRRR WAS FAIRLY REPRESENTATIVE OF WPC
EXPECTATIONS THROUGH 06Z...WITH 1-2 AND SPOT 3 INCH RAINFALL IN
FAVORED TERRAIN.

OF PARTICULAR CONCERN AT 0030Z...HOWEVER...WAS A LINE OF
CONVECTIVE CELLS IN THE CENTRAL VALLEY. ACTIVITY WAS TRAINING FROM
SOUTH TO NORTH...LOCATED FROM THE WESTERN SIDE OF SACRAMENTO UP
TOWARD OROVILLE. RADAR-BASED ECHO TOPS WERE GREATER THAN 20
KFT...BUT REFLECTIVITY WAS BOTTOM-WEIGHTED IN THE LOWEST 10 KFT.
THIS SUGGESTS THE MAJORITY OF THE PRECIPITATING ECHOES WERE BELOW
THE FREEZING LEVEL...INDICATING A WARM RAIN PROCESS. GIVEN
ANOMALOUS PRECIPITABLE WATER VALUES ABOVE 1 INCH AND UNUSUALLY
STEAD STATE TRAINING...DUAL POL ESTIMATES OF 1 TO 1.5 INCHES PER
HOUR FROM KDAX APPEARED BELIEVABLE. 

MODELS WERE NOT EXPLICITLY HANDLING THE CONVECTION...AND WERE
LOOSELY HANDLING THE AVAILABLE INSTABILITY...WITH THE NAM AND SPC
MESOANALYSIS FIELDS PERHAPS OFFERING THE BEST INSIGHT...WITH
MUCAPE OF 250-500 J/KG. IT IS HARD TO GUESS HOW LONG THE
INSTABILITY WILL LAST BEFORE BEING EXHAUSTED...AS SFC OBS TO THE
EAST WITHIN THE INFLOW WERE DRIER...BUT WITH INCREASING...AND
EVENTUALLY VERY STRONG...ASCENT...THE RAP FORECAST SOUNDINGS ARE
SUGGESTIVE OF CONVECTIVE ENHANCEMENT LASTING BEYOND 03Z. LOW LEVEL
JET WINDS WILL BACK SLIGHTLY AND ACCELERATE UPON NIGHTFALL...WITH
PERHAPS SOME TENDENCY FOR THE CELLS TO DRIFT BACK TO THE NNW. THEY
SHOULD THEN SLIDE BACK TO THE EAST AS WINDS VEER. GIVEN THIS
WAFFLING OF TRAINING CONVECTION...ISOLATED LOCATIONS NOT USUALLY
FAVORED BY THEIR GEOGRAPHY...COULD RECEIVE AN UNUSUAL AMOUNT OF
RAIN...MORE THAN 2 OR EVEN 3 INCHES...IN A SHORT 1-3 HOUR TIME
PERIOD. FLASH FLOODING IS POSSIBLE.

BURKE

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

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

LAT...LON   42222388 42002314 41722286 41652254 41642194 
            41502153 40942131 39652067 38992044 38512065 
            37972106 37602164 37662195 37992224 37692284 
            37842315 38832401 39822427 40442457 41202448 
            41832456