Hawaii Extended Forecast Discussion NWS Weather Prediction Center College Park MD 807 AM EDT Tue Apr 30 2019 Valid 00Z Wed May 01 2019 - 00Z Wed May 08 2019 Models show good agreement that an upper-level shortwave will gradually move east of Hawaii through Wed. Scattered (mostly windward) showers with locally heavy rain will be possible as this wave passes. In the wake of the shortwave, a brief period of weak upper-level ridging is expected to build across the state through Thu, bringing a somewhat drier air mass and a reduction in shower activity, and a continuation of light to moderate trades. By late week into the weekend, models/ensembles show broad agreement that a shortwave should begin to amplify near 40N/170W which is then expected to quickly deepen/close off as it dives southeast toward Hawaii. Deterministic solutions differ on the exact evolution and track of this feature, but consensus has improved somewhat relative to yesterday, with deterministic solutions now generally taking the upper low just north of Hawaii Sat-Sun. This scenario should push a cold front across the state fairly quickly from west to east Sat-Sun. Ensembles generally support this scenario, although a number of CMC ensemble members continue to take the feature a bit farther to the southwest. The scenario shown by most guidance would limit the heavy rainfall potential associated with the front due to its fairly quick forward movement, although scattered to numerous showers with locally heavy rain would be possible. A period of gusty northwest winds would also be likely in the wake of the cold front, with gradually weakening northwesterlies lingering into early next week. While seemingly a much lower probability scenario at this time, an upper low track farther to the southwest as indicated by several ensemble members would result in much different impacts for Hawaii, with a longer period of moist southerly flow and precipitation. Ryan