Hawaii Extended Forecast Discussion NWS Weather Prediction Center College Park MD 746 AM EDT Sat Sep 22 2018 Valid 00Z Sun Sep 23 2018 - 00Z Sun Sep 30 2018 Upper ridging will linger over the state this weekend. Modest moisture and trades favor light mauka/windward showers. The upper ridge drifts east of the islands early in the week. A composite of the latest models and ensembles agree that the upper low to the northwest of Hawaii early in the week moves slowly northeast with time. The trailing low level front remains west of Hawaii. The confluent flow east of the front sets up deep return moisture advection, as the models indicate potential for high 2 inch precipitable water plume to cross the western islands in the middle of the week. This supports enhanced showers and potential for locally heavy rainfall. There is a hint in both the 00z ECMWF and GFS that low level ridging builds back in later next week, keeping the moisture plume with highest precipitable water values from reaching the eastern islands. The 06z GFS hangs on to the the mid level trough west of HI longer than the GEFS mean/ecmwf/ecmwf ensemble mean, and Canadian models, so the 06z GFS could be given less weight in the forecast. Petersen