Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
805 AM EDT Mon Apr 24 2017

Valid 00Z Tue Apr 25 2017 - 00Z Tue May 02 2017

An upper ridge of high pressure and associated surface ridge will
deliver seasonable trades through Thursday. However starting on
Friday, a strong digging mid-level upper trough will begin digging
toward the state from the north and west. This will allow a strong
surface cold front to approach the state, reaching the
northwestern portion of the islands by Friday evening. The full
latitude upper trough will allow a plume of anomalous moisture
content to pool in vicinity of the state. The model guidance and
ensembles all generally show this scenario into next weekend, with
minor detail spread. In fact, operational 00z runs of gfs and
ecmwf show upper dynamics closing off, a cut-off low forming and
this circulation continuing to drop south toward the state. These
factors coming together could potentially allow heavy rainfall to
develop from Oahu to the Bis Island.

Musher