Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
809 AM EDT Thu May 03 2018

Valid 00Z Fri May 04 2018 - 00Z Fri May 11 2018

...A western island heavy rain threat may spread back across the
state next week...

Blended precipitable water loops and a composite of latest
guidance shows that a well defined moisture plume pooling along a
lingering frontal boundary has worked back northwest across the
islands. This is occurring as an upper low now near 31N/165W
tracks gradually eastward to the north of the state. This moisture
axis will linger over the western islands over the next couple of
days. A flash flood watch has been issued considering deep
moisture availabililty to fuel a threat of persistent/training
rain/convection. Global/hi-res models and ensembles indicate 
potential for locally heavy rains. Lead upper troughing moves
through by Friday. A less intense moisture axis begin to shift
southeastward and a potent mid-upper level trough digging/passing
just to the north of the state forces the reinforced trailing
front across the southern islands into Monday. This would finally
bring in drier air to the remainder of the state. A massive 1030mb
high will then bridge to the north of the state next week. Higher
PWs shift/hold just along/south of the islands and shower activity
should then be limited to windward locations next week with local
enhancements via brisk northeast trades.

Schichtel