Hawaii Extended Forecast Discussion NWS Weather Prediction Center College Park MD 730 AM EST Wed Dec 14 2016 Valid 00Z Thu Dec 15 2016 - 00Z Thu Dec 22 2016 ...Excessive rainfall threat this weekend into next week... Models and ensembles reasonably agree that sharp mid-upper level trough now digging to the northwest of the state in amplifying flow will lead to closed low development and slow passage over the islands this weekend into early next week. This powerful low is expected to induce a well organized surface low and allow for deep moisture pooling. This increase in low-level convergence combined with strengthening lift will definitely increase the coverage of showers over the region. This should be particularly the case along an old frontal zone which stalls to the south of the Big Island. Moderate to heavy rainfall is likely over the southern islands although some of the activity may remain to the south. Schichtel