Hawaii Extended Forecast Discussion NWS Weather Prediction Center College Park MD 731 AM EDT Fri May 27 2016 Valid 00Z Sat May 28 2016 - 00Z Sat Jun 04 2016 Today's model and ensemble mean guidance offers good agreement with the overall pattern through Wednesday June 1. Southeasterly low level flow on the extreme periphery of eastern Pacific high pressure will likely weaken Fri into the weekend as an upper trough passing to the north of the state brings a front through the islands, possibly as a shear line, between Saturday night and Monday. Trailing high pressure should support easterly or east-northeasterly trades in the lighter half of the spectrum Mon-Wed, weakening some by Thu. On Thursday June 2, the 06z GFS was more aggressive/westerly/slower with a system tracking along the 40th parallel, which prematurely weakens the subtropical ridge north of Hawai'i and brings a front towards the Papahanaumokuakea Marine National Monument. The 00z Canadian was faster with the system and brought the front/shear line quicker into the archipelago than the other guidance. Since the GFS has decent support aloft from the ensemble means, prefer a compromise of the 06z GFS/00z ECMWF Thursday into next Friday and maintain the subtropical ridge longer than the GFS suggests. Expect best potential for some precipitation to have a sea breeze focus this weekend when guidance anticipates the lightest trades and a front/shear line passing through the island chain. Above normal precipitable water values at the start of the period will trend toward climatology by late weekend/early next week, then perhaps drift a bit higher again late next week as the next frontal boundary approaches. Roth