Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
814 AM EDT Fri May 04 2018

Valid 00Z Sat May 05 2018 - 00Z Sat May 12 2018

...A showery period continues for the Big Island...

The models and ensemble indicate the tail end of a cold front in
the central Pacific drifts east across the islands over the
weekend.  An enhanced plume of  precipitable water supports
enhanced shower activity today.  As the front moves east, the
coverage and amounts of rain decline as the weekend progresses as
both the departure of the upper trough and gradual approach of the
upper ridge from the northwest support drier air advecting into
the islands starting in the west and then into the central islands.

High pressure builds north of the islands in the early to middle
parts of next week, so the remnant frontal boundary dies and the
flow gradually becomes easterly with moderate trade winds
returning. The high available moisture over the big Islands
provides potential for above normal rainfall amounts with activity
focused in locations with enhanced upslope flow and in areas with
enhanced coastal convergence. The models and ensembles have better
than average agreement so small differences can be handled using a
consensus based approach.

Petersen