Hawaii Extended Forecast Discussion NWS Weather Prediction Center College Park MD 812 AM EDT Mon Mar 26 2018 Valid 00Z Tue Mar 27 2018 - 00Z Tue Apr 03 2018 A lingering surface boundary is expected to gradually wash out across Hawai'i over the next few days, keeping some degree of moisture lingering, especially across the eastern islands. This will keep the potential for showers in the picture perhaps into midweek before drier air overtakes the region. The best chance for any additional locally heavy rains should be along the southern coast of the Big Island. Models/ensembles continue to show general agreement that heights will gradually rise across Hawai'i through mid-week with drier air gradually advecting across the state. Low-level flow should be very light through mid-week, with easterlies resuming by late in the week. A trough/upper low is expected to amplify along 170W by late in the week, and the GFS/ECMWF continue to show a front approaching by next weekend. The GFS remains a bit quicker to move the front east, bringing an increased threat of showers into the western islands by next Sat, while the ECMWF would hold the showers a couple hundred miles farther west. At this time a compromise solution is favored, which would bring at least a chance of showers into the western islands by next weekend, but perhaps with the most widespread activity remaining farther west. Ryan