Hawaii Extended Forecast Discussion NWS Weather Prediction Center College Park MD 817 AM EDT Thu Apr 05 2018 Valid 00Z Fri Apr 06 2018 - 00Z Fri Apr 13 2018 Latest guidance seems to be coming together in principle for details of the forecast which will feature a period of heavy rain potential in association with moisture along a decelerating cold front that is currently approaching from the northwest. Strong mid-latitude dynamics passing to the north of the state over the coming day will push the aforementioned front into the area late this week, likely stalling not far from the Big Island. Expect moist southwesterly flow ahead of the front followed by moderate trade flow and eastward-facing terrain focus behind the front as a weak surface ridge rapidly moves along 30N latitude. Even with some differences in QPF depictions among the models/ensembles, this weekend shows the best signal for heavier rainfall. An approaching upper shortwave will interact with the southwest-northeast band of high moisture (precipitable water values of at least 1.50-2.00 inches) persisting over the islands, with some surface troughing noted from Saturday into Sunday or Monday which may provide some added low level focus. A stronger surface high than its predecessor will progress along 30-35N latitude will bring stronger trade flow Tuesday onward with highest wind speeds likely around Wednesday when the surface gradient appears tightest. A weak ridge aloft will build northwest-north of the state late in the period as well. This evolution and lingering moisture/shortwave energy over the state should maintain shower activity favoring but not limited to windward terrain. Note that around Tue the 06z GFS is in the minority, pushing the moisture axis farther southeast than the 00z GFS/GEFS mean/ECMWF. With some differences in timing, most guidance suggests that the ridge to the north of the islands at the surface and aloft will ultimately help to push the axis of greatest deep moisture westward by Wednesday-Thursday. Rausch