197 FXHW60 PHFO 300600 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 800 PM HST Sun Sep 29 2019 .SYNOPSIS... Typical trade wind weather will prevail through the work week, with moderate to breezy trade winds expected. Clouds and showers will favor windward and mauka areas, with a few showers spilling over into leeward communities from time to time. The trades will ease next weekend, with a decrease in shower activity also expected. && .DISCUSSION... Currently at the surface, a pair of high pressure systems are situated far north-northeast and far north-northwest of the state, with a weakening front in between these two features around 600 miles due north of Honolulu. Moderate trade winds prevail across the island chain this evening. Infrared satellite imagery shows partly to mostly cloudy skies in windward areas, with clear to partly cloudy conditions in leeward locales. Radar imagery shows scattered showers moving into windward areas, with a few showers spilling over into leeward communities from time to time. Main short term concern revolves around the strengthening trade winds. The weakening front north of the state will slowly dissipate over the next couple days, while the two areas of high pressure merge into a single far northeast of the islands. This will lead to a strengthening of the trades over the next couple days, with breezy conditions expected Tuesday through Thursday. The trades should begin to trend down slightly on Friday, with a further easing expected over the weekend as a deep upper level trough and surface cold front dig southward toward the islands. Typical trade wind weather will prevail through the work week, with scattered to numerous windward showers, and a few showers occasionally spilling over into leeward communities. Showers will be most prevalent from 6 pm through 10 am of so each day, with a typical decrease in shower coverage during the late morning and afternoon hours. As the trade winds diminish next weekend, we should see a bit of a decrease in shower activity across the island chain. && .AVIATION... With the exception of brief periods of MVFR ceilings and vis in associated with the trade wind showers, VFR conditions will prevail across the area during the overnight and morning hours. These showers will favor windward and mountain areas of all islands. A shower or two will venture further downwind into the lee areas of the smaller islands. The leeward coast and adjacent waters of the Big Island may also have a late night shower or two. A ridge of high pressure located far north of the islands will be providing moderate to locally strong trade winds to the area for at least the next 24 hours. We will be monitoring for low level turbulence overnight. Conditions are marginal right now for low level turbulence and AIRMET Tango. There are no AIRMETs currently in effect, and none are expected overnight and Monday morning. && .MARINE... Fresh to strong trade winds associated with high pressure north- northeast of the state will continue through much of the week. Expect the strongest winds across the channels, especially from Maui County to the Big Island. Trades will trend down next weekend as a weakness develops in the ridge in response to a front passing to the north. A small northwest swell is expected Monday, which will keep the surf from going flat along north and west facing shores through Tuesday. For the extended, guidance does depict a gale developing and tracking north-northeast across the Date Line around 1800 miles northwest of the islands Tuesday through Thursday. A small north-northwest swell from this source will become a possibility next weekend. Surf along south facing shores will lower through Tuesday as the current south swell fades. A small south-southwest swell will be possible through the second half of the upcoming week. Surf along east facing shores will rise through Monday as a northeasterly swell associated with a pocket of strong northeast winds off the California coast fills in locally. This combined with strengthening trades will translate to rough surf, which should continue through the week. A downward trend is likely through the upcoming weekend as the trades diminish locally and upstream. && .HFO WATCHES/WARNINGS/ADVISORIES... Small Craft Advisory until 6 PM HST Tuesday for Maalaea Bay- Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters. && $$ DISCUSSION...Jelsema AVIATION...Lau MARINE...Gibbs