Hawaii Extended Forecast Discussion NWS Weather Prediction Center College Park MD 708 AM EST Wed Feb 21 2018 Valid 00Z Thu Feb 22 2018 - 00Z Thu Mar 01 2018 An upper low is forecast to form later today to the northwest of the area with a downstream narrow ridge along 150W. This will allow deep tropical moisture to surge northward across the state with locally moderate to heavy rain and embedded thunderstorms. Precipitable water values are forecast to rise to between about 1 1/3 to 1 3/4 inches through the period which is well above average for late February. Another upper low may form next week just west of 170W which may pull the precipitable water axis westward next week, perhaps west of Kauai/Ni'ihau. Fracasso