031  
FXHW01 KWNH 180744  
PMDHI  
 
HAWAII EXTENDED FORECAST DISCUSSION  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
343 AM EDT THU MAY 18 2023  
 
VALID 00Z FRI MAY 19 2023 - 00Z FRI MAY 26 2023  
 
A WET PATTERN IS IN STORE FOR HAWAII FOR THE LATTER PART OF THIS  
WEEK AS AN UPPER TROUGH MOVES ACROSS THE STATE. ANOMALOUSLY HIGH  
TROPICAL MOISTURE WILL STREAM IN WITH THE DEEP SOUTHERLY FLOW  
WITH/AHEAD OF THIS FEATURE, PROVIDING FOR WIDESPREAD RAIN. SOME  
THUNDERSTORMS MAY BE POSSIBLE AS THE TROUGH ALOFT COULD LESSEN OR  
OR ELIMINATE THE TYPICAL INVERSION AND PROVIDE INSTABILITY, BUT A  
LIMITING FACTOR FOR STRONG STORMS COULD BE THE WIDESPREAD CLOUD  
COVER REDUCING SURFACE HEATING. REGARDLESS ENHANCED RAINFALL  
TOTALS ARE LIKELY ACROSS ESPECIALLY THE WESTERN ISLANDS  
THURSDAY-FRIDAY, WHERE THE LOCAL WEATHER FORECAST OFFICE HAS A  
FLOOD WATCH IN PLACE, AS KAUAI/OAHU ARE LIKELY TO SEE THE BEST  
COMBINATION OF MOISTURE AND DYNAMICAL SUPPORT FOR HEAVY RAIN.  
SHOWERS WITH POTENTIALLY HEAVY RAIN RATES CAN STILL BE EXPECTED  
FOR THE EASTERN PART OF THE STATE THOUGH.  
 
SHOWER COVERAGE SHOULD GRADUALLY DECREASE THROUGH THE WEEKEND AS  
THE WEAKENING UPPER TROUGH MOVES AWAY AND IS REPLACED BY AN UPPER  
RIDGE. THIS WILL SHIFT THE MOISTURE PLUME WEST OF THE STATE NEXT  
WEEK WHILE SURFACE HIGHS BUILD TO THE NORTHEAST AND EVENTUALLY THE  
NORTHWEST TOO, CREATING A MORE TYPICAL AND DRIER EASTERLY TRADE  
WIND PATTERN. TRADES MAY INCREASE TO BREEZY LEVELS AT TIMES NEXT  
WEEK, AND SHOWERS THAT DO FORM SHOULD FOCUS ACROSS WINDWARD AND  
MOUNTAIN AREAS.  
 
TATE  
 

 
 
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