Hawaii Extended Forecast Discussion NWS Weather Prediction Center College Park MD 716 AM EST Sun Dec 11 2016 Valid 00Z Mon Dec 12 2016 - 00Z Mon Dec 19 2016 ...Heavy rainfall threat for next weekend... The upper trough to the north of the state coupled with the surface trough to the southwest will provide a pathway for continued showers into Monday. Cold front or shear axis will push through the region early Tuesday and turn winds to northerly behind the boundary. Weak/brief ridging on Wednesday should mean a relatively dry day with continued veering trades to northeasterly and then easterly. By Thursday, split flow in the central north Pacific will promote ridging into the Gulf of Alaska and a closed low well to its south. Ensembles have trended a bit closer/deeper/slower by Friday with the upper low and the ECMWF ensembles have trended toward the more consistent GEFS ensembles (Canadian ensembles have gone the other way to a more northerly and quicker solutions, which is not preferred). The 00Z ECMWF/UKMET and 06Z GFS form a good cluster between the farther southwest 00Z GFS and farther northeast 00Z parallel GFS by Friday. This is near the 06Z GEFS mean. By the weekend, many of the ECMWF ensembles were quicker to move the upper low eastward but the GEFS ensembles stall the upper low just to the west of Hawai'i, like the deterministic GFS/ECMWF. Amplified pattern and trends in the guidance support a closed low that may very well stall just west of the 50th state, which would be a setup for heavy rainfall as shown in some of the guidance. However, a shift to the east with the upper low position may guide the moisture axis east of the region. Ensemble range in 7-day precipitation is very large -- from about a half inch to over 15 inches over the central/eastern islands. Fracasso