Hawaii Extended Forecast Discussion NWS Weather Prediction Center College Park MD 814 AM EDT Sat Apr 22 2017 Valid 00Z Sun Apr 23 2017 - 00Z Sun Apr 30 2017 High pressure on its way to settling over the eastern Pacific, and its ridge extending westward, will support at least moderate trades through midweek. Based on changes in the pressure gradient there should be a modest weakening trend between now and early Monday, and a slightly stronger trend Monday into early Wednesday. Moisture initially over the northwestern half of the state will lift away to yield drier conditions early in the week with any rainfall tending to favor windward locales. There may be some increase in precipitable water values around midweek. During the latter half of the week into the weekend model/ensemble guidance continues to show a lot of spread for an amplified trough forecast to approach and possibly reach the state. There will likely be a wavy surface front ahead of this trough. In varying ways latest GFS/CMC runs are not as extreme aloft compared to yesterday. The 00z GFS run is still on the deeper part of the spread with the trough with the 06z GFS a little weaker and eastward with its core, and while the 00z GEFS mean is the most amplified among the means the operational 00z ECMWF offers potential for somewhat greater amplitude for the southern part of the upper trough than the 00z ECMWF mean. The 00z ECMWF shows a westward trend from its prior 12z run. Overall based on the full array of guidance and embedded trends a compromise between the 06z GFS and 00z ECMWF appears to be the best starting point at this time. In association with this evolution, by Friday-Saturday there may be a north-south band of enhanced moisture aligned over/near the islands with increased rainfall potential. Rausch