Hawaii Extended Forecast Discussion NWS Weather Prediction Center College Park MD 815 AM EDT Wed Aug 23 2017 Valid 00Z Thu Aug 24 2017 - 00Z Thu Aug 31 2017 Surface high pressure north of the state is forecast to all guidance to gradually weaken over the next several days as a broad area of negative height anomalies develops across the north central Pacific. By the middle of next week, models generally show some degree of ridging reestablishing itself northeast of the Hawaiian Islands, resulting in a broad mid/upper-level blocking pattern across the north and central Pacific. The weakening surface high north of the Islands should result in a slight weakening of the trades through early next week. A relatively dry air mass advect across Hawaii initially, with precipitable water values decreasing into the 1.00-1.30 inch range, which should suppress shower activity to a degree. A tropical wave is expected to pass south of Hawaii Sunday and Monday, which could result in a moisture increase primarily for the Big Island (PWATS increasing to 1.7-2.00 inches per the 00z ECMWF, a bit less per the 06z GFS). Thus, expect the potential for an increase in shower activity across the Big Island by Sunday or Monday. In the wake of this moisture surge, easterlies should pick up a bit, as the ridge reestablishes itself northeast of Hawaii. Ryan