Hawaii Extended Forecast Discussion NWS Weather Prediction Center College Park MD 816 AM EDT Thu Apr 26 2018 Valid 00Z Fri Apr 27 2018 - 00Z Fri May 04 2018 A rapidly amplifying central Pacific trough aloft will close off an upper low to the north of the state by Friday, reaching as far south as 30-35N latitude by late Friday into the weekend. The upper low will begin to lift northeastward during the first half of next week. After early Monday heights over the island will rise somewhat but a northeast-southwest trough should persist to the north through midweek. Developing low pressure associated with the upper low will anchor a front that passes through the state from west to east during Friday-Sunday. There will be potential for some bands of locally heavy rainfall along the front as deep moisture increases. Trade flow currently in place will become southeasterly ahead of the front and northerly behind the front. After Sunday the front and axis of highest precipitable water values will remain close enough to the Big Island, or perhaps lift back to the northwest a bit given the rise in heights aloft, to support a heavy rainfall threat at times over the eastern part of the state. Differences in location of the front/moisture axis as well as details aloft are well within typical guidance error for 5-7 day forecasts and at this time show no pronounced clustering. Thus confidence in any specific solution is not particularly high, recommending an intermediate solution for forecast specifics. The western islands should see a drier pattern next week with relatively light windward showers. Most guidance expects west-central Pacific high pressure gradually building eastward to promote a strengthening of northeasterly winds by next Wednesday-Thursday. Rausch