641  
FXHW01 KWNH 161229  
PMDHI  
 
HAWAII EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
728 AM EST SAT DEC 16 2017  
 
VALID 00Z SUN DEC 17 2017 - 00Z SUN DEC 24 2017  
   
..HEAVY RAIN THREAT NEXT WEEK
 
 
A SLOW MOVING UPPER LOW WILL KEEP CONDITIONS UNSETTLED OVER THE  
ISLANDS ON SATURDAY, BUT THEN THE CHANCE FOR SHOWERS SHOULD BEGIN  
TO DECREASE SUNDAY INTO MONDAY AS THE LOW GRADUALLY WEAKENS AND  
LIFTS NORTHEASTWARD. THE THREAT FOR HEAVY RAIN IS EXPECTED TO  
QUICKLY RETURN MONDAY NIGHT INTO TUESDAY AND WEDNESDAY WHILE AN  
UPPER TROUGH AMPLIFIES ALOFT AND A FETCH OF DEEP TROPICAL MOISTURE  
REACHES THE ISLANDS. CONDITIONS SHOULD IMPROVE BY LATE NEXT WEEK  
ONCE THE FEED OF MOISTURE SHUNTS EASTWARD WITH THE MEAN TROUGH  
AXIS.  
 
MODEL GUIDANCE IS IN FAIRLY GOOD AGREEMENT WITH THE LARGE SCALE  
PATTERN SETTING UP OVER THE ISLANDS THIS WEEKEND AND THROUGH NEXT  
WEEK. HOWEVER, THERE IS STILL SOME UNCERTAINTY WITH THE DETAILS  
OF THE AMPLIFYING UPPER TROUGH.  
 
GERHARDT  
 

 
 
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