Hawaii Extended Forecast Discussion NWS Weather Prediction Center College Park MD 806 AM EDT Thu Mar 15 2018 Valid 00Z Fri Mar 16 2018 - 00Z Fri Mar 23 2018 ...Heavy rain threat... Mid-latitude high pressure has shifted into the eastern Pacific and island trades underneath are moderating. Surface low pressure/mid-level trough energies have meanwhile lifting over the state. Deep moisture is feeding into the islands with precipitable water values now about 2 inches (3+ standard deviations). This is supported by a favored guidance composite and satellite/blended loops. This is fueling a wet period over the next few days with potential for local heavy rainfall and runoff issues. A flash flood watch has been issued for the western islands and a flash flood warning was in effect for eastern Maui. A winter weather advisory is in effect for Mauna Loa and Mauna Kea summits on the Big Island. Models/ensembles agree to develop an upper trough or closed low near 25N/180 Friday/Saturday which should allow heights over Hawai'i to rise, gradually lessening the heavy rain threat over the weekend. However, southeasterly trades persist into next week with lingering scattered and windward terrain enhanced showers with slightly lower banded precipitable water values. Later, a slow as translation of the mid-upper level low/trough and deepening surface low from the west may allow an lead frontal system with renewed lead moisture inflow/height falls and convective precipitation potential reach the islands next midweek. Guidance is varied with amplitude of the gradually lifting feature, but there is an overall good signal for system occurance. Schichtel