465  
AWUS01 KWNH 211454  
FFGMPD  
CAZ000-220000-  
 
MESOSCALE PRECIPITATION DISCUSSION 0078  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1053 AM EDT TUE MAR 21 2017  
 
AREAS AFFECTED...N-CNTRL...CNTRL AND SRN CA  
 
CONCERNING...HEAVY RAINFALL  
 
VALID 211452Z - 220000Z  
 
SUMMARY...INCREASING INSTABILITY IS EXPECTED TO SUPPORT RAINFALL  
RATES UP TO 1 IN/HR IN THE NRN SAN JOAQUIN VALLEY AND THE  
FOOTHILLS OF THE SIERRAS AFTER 18Z. FARTHER SOUTH...LOCALIZED  
RAINFALL RATES OF 0.5 IN/HR WILL BE POSSIBLE LATE THIS MORNING TO  
THE EARLY AFTERNOON WITH THE THREAT DIMINISHING INTO THE LATE  
AFTERNOON.  
 
DISCUSSION...A 24 HR LOOP OF THE LAYERED PW PRODUCT SHOWED THE  
MERGING OF TWO STREAMS OF HIGHER MOISTURE IN THE 850-700 MB LAYER  
FOCUSED INTO THE CNTRL CA COAST...COINCIDENT WITH THE GREATEST  
WATER VAPOR FLUX IN THE TROPOSPHERE. THE RESULT IN THE BLENDED TPW  
PRODUCT WAS A LARGE AREA OF ANOMALOUS MOISTURE WITH 1+ INCH  
PRECIPITABLE WATER VALUES WHICH EXTENDED FROM THE NRN SACRAMENTO  
VALLEY TO THE LOS ANGELES METRO AREA AS OF 14Z. A LARGE CLOSED LOW  
WAS OBSERVED ON WATER VAPOR IMAGERY OFFSHORE OF NRN CA WITH STEADY  
HEIGHT FALLS SHIFTING EAST ALONG WITH A COLD FRONT AT THE SURFACE.  
 
DESPITE EXTENSIVE CLOUD COVER SEEN ON IR SATELLITE IMAGERY ACROSS  
MUCH OF CA...THE COMBINATION OF DAYTIME HEATING AND COOLER  
MID-LEVEL TEMPERATURES ASSOCIATED WITH THE ADVANCING CLOSED LOW  
WILL SUPPORT INCREASING INSTABILITY INTO THE CNTRL CA VALLEY WITH  
A CONSENSUS OF THE LATEST RAPIDLY UPDATING MODELS INDICATING  
ANYWHERE FROM 250 TO 750+ J/KG OF CAPE DEVELOPING OVER THE CNTRL  
AND NRN SAN JOAQUIN VALLEY BETWEEN 18-00Z. WHILE PRECIPITABLE  
WATER VALUES AND SUBSEQUENT INTEGRATED VAPOR TRANSPORT WILL BE  
FALLING INTO THE AFTERNOON...UNIDIRECTIONAL FLOW FROM THE  
SOUTHWEST WITH A STEADY 25-30 KTS OF 850-700 MB FLOW MAY SUPPORT A  
FEW AREAS OF TRAINING HEAVY RAIN AHEAD OF THE ADVANCING COLD  
FRONT. DIFFLUENT FLOW ALOFT AND THE ADDED UPSLOPE COMPONENT TO THE  
FLOW INTO THE SIERRA NEVADA SHOULD HELP MAKE UP FOR THE LOSS OF  
MOISTURE TO SUPPORT RAINFALL RATES OF 0.5 TO 1.0 IN AT TIMES THIS  
AFTERNOON.  
 
FARTHER SOUTH...THE BEST MOISTURE FLUX WILL BE DIRECTED INTO THE  
TRANSVERSE RANGES OF SRN CA OVER THE NEXT 6 HOURS WITH A FOCUS  
INTO THE SANTA YNEZ...SAN RAFAEL...AND SIERRA MADRE RANGES FOR  
RAINFALL RATES POTENTIALLY REACHING 0.5 IN/HR. HOWEVER...AS THE  
UPPER TROUGH CONTINUES TO ADVANCE EAST TODAY...PRECIPITABLE WATER  
VALUES ARE FORECAST TO GRADUALLY DIMINISH ALONG WITH WEAKENING LOW  
LEVEL FLOW WHICH SHOULD GREATLY REDUCE THE HEAVY RAINFALL THREAT  
AFTER 21Z FOR SRN CA.  
 
OTTO  
   
..PLEASE SEE WWW.WPC.NCEP.NOAA.GOV FOR GRAPHIC PRODUCT
 
 
ATTN...WFO...HNX...LOX...MTR...STO...  
 
ATTN...RFC...CNRFC...  
 
LAT...LON 39942137 39722099 39432066 38992037 38201994  
37661967 37401936 36981884 36461855 36131843  
35631843 35011838 34431869 33931923 33872031  
34782099 35682165 36542219 38222245 39072224  
39682184  
 
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