Hawaii Extended Forecast Discussion NWS Weather Prediction Center College Park MD 729 AM EST Thu Feb 08 2018 Valid 00Z Fri Feb 09 2018 - 00Z Fri Feb 16 2018 A band of mid-latitude height falls migrating eastward will give way to a separation in the flow as a closed low peels off in the vicinity of 20N/150W by Friday night. This ultimately leads to a rex block pattern to the east of the Hawai`ian island chain while renewed upper troughing sets up over the central Pacific. The southern extent of these lower heights take aim at the state by Tuesday with sufficient clustering noted in the 564-dm ensemble spaghetti plots. There is a growing model consensus that another closed low will develop upstream of Hawai`i by late Tuesday with other guidance now joining the GFS solution. By early Wednesday, there are a fair amount of 00Z GEFS and ECMWF ensemble members depicting such a negative height anomaly lingering over the region. A vast majority of the 00Z CMC ensemble solutions reject this idea although the operational run depicts its presence. Beyond this period, the upper low is forecast to drift eastward with a location likely just east of the state by next Thursday afternoon. In the wake of the frontal passage, low-level cold advection should continue as general northerly flow persists. It could become quite breezy at times with sustained winds around 20 knots expected. As a weak surface cyclone moves southeast of the Big Island by late in the weekend, surface winds turn more east-northeasterly with a decrease in strength. By early next week, a warm advection regime ensues ahead of a sharp north/south oriented baroclinic zone. Depending on the timing of this system, the next frontal passage will occur by the middle of next week with wind fields quite variable across Hawai`i as the wave sits over the region. Regarding precipitation threats, scattered showers should be in the process of exiting the Big Island with drier conditions to prevail in the wake. There could be a threat for some disorganized light precipitation over the weekend as a plume of higher precipitable water pivots back over the state. A much wetter period is likely next week, particularly as the frontal zone drifts slowly toward the east. It should be a fairly wet system as precipitable water values near 1.50 inches by the middle of the week. Rubin-Oster