Hawaii Extended Forecast Discussion NWS Weather Prediction Center College Park MD 300 AM EST Mon Dec 06 2021 Valid 00Z Tue Dec 07 2021 - 00Z Tue Dec 14 2021 ...Significantly heavy rainfall potentially causing catastrophic flooding could continue through Tuesday... Heavy rain currently occurring over Hawaii is forecast to continue over the next couple of days. A kona low is located to the west of the state (with a stacked mid-upper low and surface low), leading to deep layer southerly flow directing tropical moisture northward from the ITCZ. Model guidance agrees that precipitable water values over the 95th percentile will last through at least Tuesday, with the axis of highest PWs drifting slowly east to west across the state as a couple of surface troughs focus the moisture. Several inches of rain have already fallen across parts of the Big Island, and as of Sunday night, the heaviest rainfall is winding down there as the heavy rain drifts westward into Maui and nearby islands. Oahu can expect heavy rain to begin later Sunday night, with Kauai seeing its heaviest totals on Monday into Tuesday. Across the state, flooding and flash flooding, landslides and debris flows, road closures, and low visibility with high rainfall rates are all possible or expected. In total, widespread rainfall amounts are forecast to be 10 to 15 inches with isolated areas of 20 to 25 inches. Strong winds are also a continued threat through Sunday night, lessening on Monday. By the second half of the week, the kona low is forecast to drift westward while an upper high encroaches toward Hawaii, eventually lessening heavy rain chances as a more typical easterly trade wind pattern sets up. Tate