MESOSCALE PRECIPITATION DISCUSSION 0046
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
110 PM EST SUN MAR 06 2016
 
AREAS AFFECTED...COASTAL SW OREGON...NW CALIFORNIA 
 
CONCERNING...HEAVY RAINFALL 
 
VALID 061815Z - 070315Z
 
SUMMARY...COMPACT WAVE TO SPLIT FOCUS FOR HEAVY RAINFALL WITH
COMMA HEAD CONVECTION NEAR SURFACE LOW IN SW OR AND BETTER
MOISTURE/ASCENT NEAR COLD FRONT ACROSS NW CA FROM 22Z-03Z.

DISCUSSION...A LOW AMPLITUDE SHORTWAVE IS STREAKING TOWARD THE
OR/CA COAST UNDER STRONG UPPER LEVEL FLOW THAT BECOMES
INCREASINGLY DIFFLUENT NEAR THE COAST ALLOWING THE FOCUS TO
SPLIT...NORTH WITH THE SURFACE LOW INFLECTION AND SOUTH OF CAPE
MENDOCINO WITH COLD FRONT/ONSHORE MOISTURE FLUX.  GIVEN THE SYSTEM
IS WITHIN THE LARGER UPPER LEVEL COLD POOL...THE WAVE HAS SOME
STEEPER LAPSE RATES TO SUPPORT WEAK INSTABILITIES (250-500 J/KG)
ALLOWING FOR SOME DEEPER CONVECTIVE GROWTH.  VISIBLE IMAGERY
ALREADY DEPICTS THIS CONVECTIVE NATURE NEAR THE SURFACE CYCLONE
WITH TOPS TO -50C.  THIS CLUSTER SHOULD CONTINUE TO ENHANCE DUE TO
LOW LEVEL MST CONVERGENCE FROM ISALLOBARIC COMPONENT
WINDS...THOUGH THE MOISTURE WILL BE A BIT MORE LIMITED AS THE E-W
ORIENTED DEEPER MOISTURE FURTHER SOUTH...THE MST FLUX CONVERGENCE
AND DPVA WILL KEEP CORE STRONG ENOUGH TO SUPPORT RATES OF 1.0"/HR
AS THEY NEAR THE OR COAST NORTH OF CAPE BLANCO...WITH SIMILAR
RAINFALL TOTALS POTENTIALLY LEADING TO SHORT TERM FLOODING
CONCERNS.  THE LIMITING FACTOR.

BLENDED TPW IMAGERY INDICATES A SMALL SLUG OF ENHANCED MOISTURE
ALONG/JUST SOUTH OF THE COLD FRONT...WITH VALUES NEAR 1.0" AS THE
SURFACE WAVE AMPLIFIES IN THE NEXT FEW HOURS...LOW LEVEL SSWLY
FLOW WILL INCREASE TO 45-55 KTS AHEAD OF THE FRONT AND GIVEN A
SIMILAR INSTABILITY SETUP SHOULD SUPPORT INCREASED CONVECTIVE
GROWTH ALONG THE COLD FRONT AS WELL. ALOFT THE UPPER LEVEL JET
AXIS IS TURNING SLIGHTLY SOUTHEAST WITH ANTICYCLONIC RIDGING
PROVIDING ADDITIONAL LEFT EXIT DIVERGENCE WITHIN THE TIGHT ISOTACH
GRADIENT IN THE VICINITY TO PRODUCE EVEN STRONGER CONVECTION
CAPABLE OF RATES NEARING 1.25"/HR AS THE COLD FRONT MOVES ASHORE
SOUTH OF THE CAPE BY 22Z. ORIENTATION OF THE FLOW WILL BE MORE
WESTERLY...SO SOUTHWARD SHIFT OF THE COLD FRONT-COAST INTERSECTION
WILL BE SLOW WITH THE POTENTIAL OF SOME ACCIDENTAL TRAINING OF
SOME OF THE MORE INTENSE CORES...EVENTUALLY NEARING N SONOMA
COUNTY BY 03Z...AFTER THIS POINT BEST FORCING IS REDUCING WITH
LOWERING ONSHORE 850MB FLOW. THREAT FOR FLOODING CONDITIONS ARE
MORE LIKELY IN THIS SOUTHERN ZONE DRIVEN MAINLY BY THE RATES BUT
ALSO ANTECEDENT CONDITIONS FROM THE LAST FEW ROUNDS OVER THE LAST
FEW DAYS.       

GALLINA

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

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

LAT...LON   44822324 44002283 42262367 41282295 40492238 
            39932195 39082188 38402214 38012266 38102333 
            38882400 40012468 41132477 42072497 43142521 
            44232485 44762431