Graphic for MPD #0049
MESOSCALE PRECIPITATION DISCUSSION 0049
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1239 PM EST THU FEB 09 2017
 
AREAS AFFECTED...CALIFORNIA 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 091800Z - 100400Z
 
SUMMARY...SUBTROPICAL MOISTURE STREAM WILL SLOWLY SINK ALONG THE
CALIFORNIA COAST THIS AFTERNOON INTO EVENING WITH SLOW REDUCTION
OF MST FLUX/RAINFALL RATES. YET RATES OVER .5"/HR REMAIN LIKELY
WITH A THREAT OF FLASH FLOODING GIVEN ANTECEDENT CONDITIONS.  

DISCUSSION...POLAR 89GHZ FROM AMSU/SSMIS ALONG WITH TRADITIONAL
IR/SHORTWAVE IR LOOP DEPICT A STRONG SHORTWAVE AND ASSOCIATED
SURFACE INFLECTION RAPIDLY MOVING TOWARD THE W WA COAST WEST OF
THE MOUTH OF THE COLUMBIA RIVER AT THIS TIME...WITH A COLD FRONT
EXTENDING SOUTHWARD ALONG THE WESTERN EDGE OF HIGHER CIRRUS
COLLOCATED WITH THE WARM CONVEYOR BELT/DEEP MOISTURE STREAM.  THIS
MOISTURE STREAM PER BLENDED TPW EXTENDS JUST SOUTH OF THE OR/CA
BORDER AT THE COAST WITH UNFORTUNATELY CONVECTIVE FEEDBACK
ANOMALIES ALONG IT.  VALUES ARE AROUND 1.2-1.3" PER GPS NETWORK
ALONG THE COAST REACHING 1.5" ABOUT 50-100 MILES FROM SHORE. 
CURRENTLY THE FLOW REMAINS STRONG AND FAIRLY UNIDIRECTIONAL MINUS
SUB-BOUNDARY LAYER SOUTHERLY WINDS IN THE TIGHTER GRADIENT
ASSOCIATED WITH THE EXITING SHORTWAVE WITH 50-60KT 85H WINDS.  THE
HEIGHT FALLS FROM THE STEADILY EASTWARD PROGRESSION OF THE UPPER
LEVEL TROF CONTINUE TO HELP SHUNT THE COLD FRONT EASTWARD AND
THEREFORE SOUTHWARD ALONG THE COAST.  THIS RATE OF SOUTHWARD
PROGRESSION SHOULD BE STEADY BUT WITH REDUCING WINDS TOWARD 40KTS
BY 20Z NEARING THE BAY AND 30KTS ACROSS THE CENTRAL SANTA LUCIA
RANGE BY 01Z...YET THE FLOW IS INCREASING IN ANGLE TO THE COAST
BECOMING NEARLY PERPENDICULAR BY THE TIME THE MAIN AXIS REACHES
SANTA CRUZ MOUNTAINS/MONTERREY BAY.

AS SUCH RAIN RATES WILL START AT .5 TO .75"/HR FURTHER NORTH
ACROSS THE NORTH BAY BUT MAINTAIN TO AT LEAST .5" INTO THE SANTA
LUCIA AROUND 03Z.  RAP SOUNDINGS IN THE CENTRAL VALLEY SUGGEST
SOME WEAK INSTABILITY (100-150 J/KG) AND WITH STRONG MOISTURE
CONVERGENCE/OROGRAPHIC ASCENT MAY SPARK SOME WEAK CONVECTIVE
ELEMENTS ON THE SOUTHEAST LOWER FLANKS OF THE SIERRAS.  THOUGH THE
DURATION OF THESE RATES WILL BE LIMITED GIVEN THE SOUTHWARD PUSH
OF THE MOISTURE AXIS... THE RATES AND SATURATED ANTECEDENT
CONDITIONS POSE A FLASH FLOODING THREAT AND DEBRIS FLOWS.  HI-RES
GUIDANCE PARTICULARLY THE ESRL EXP. HRRR AND 12Z WRF-ARW ARE
FAIRLY AGREEABLE/USEFUL ESPECIALLY IN TIMING WHILE THE LAST FEW
RUNS OF THE OPERATIONAL HRRR WHILE ON PAR WITH RATES APPEARS MUCH
SLOWER.  

GALLINA

ATTN...WFO...EKA...HNX...LOX...MFR...MTR...REV...STO...VEF...

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

LAT...LON   41772218 41402155 40902133 40372106 40052066 
            39642037 38892012 37961923 37361870 36951872 
            36821927 37011994 36952052 36762062 36282031 
            35852023 35482046 35352087 35642126 36242195 
            36612220 37032243 37612270 37922299 38522346 
            38892375 39332388 39762406 40242400 40612386 
            40972356 41512274 


Last Updated: 1239 PM EST THU FEB 09 2017