761 FXHW60 PHFO 230656 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 856 PM HST Mon Apr 22 2019 .SYNOPSIS... A trade wind weather pattern will continue through the work week, with periods of clouds and showers expected to favor windward areas. Leeward areas will remain mostly dry. The trades will begin to decrease over the weekend, allowing for development of sea and land breezes. This will favor showers developing over leeward and interior sections of the islands during the daytime. && .DISCUSSION... A 1031 mb high far northeast of Hawaii is driving locally breezy trade winds across local waters this evening. Our airmass remains dry and stable, with weak upper ridging over the area. Afternoon soundings show strong inversions between 5000 to 6000 ft and PW between 0.9 and 1.1 inches. Satellite loop shows scattered to patchy broken low clouds over windward sections of the islands. Radar shows a few showers are associated with the low clouds. Leeward areas are mostly clear this evening. Kona cloud cover on the Big island is beginning to fade away as evening cooling sets in. Models show trade winds will maintain speed through Wednesday, then weaken slightly towards the end of the work week. Low clouds and scattered showers will continue to push over the islands, focusing over windward and mauka areas. These showers will generally be light and occur mostly during the overnight and early morning hours. Warm and mostly sunny conditions will continue for leeward areas. Over the weekend, a weak surface trough will develop over the islands in response to an approaching upper trough. This will result in the trade winds weakening, veering east southeastly and allowing daytime sea breezes and nighttime land breezes to set up. A weak front will also approach the islands from the northwest, but will likely fade before reaching Kauai. This weekend, expect an overall increase in clouds and showers, particularly across leeward and interior sections of the islands during the daytime. Models disagree on the strength of the forecast upper trough, with GFS showing a weaker trough than depicted in ECMWF. There is potential for locally heavy rainfall and/or thunderstorms on Sunday and Monday, but given the model differences that far out in the forecast period, we will delay adding these to the grids. && .AVIATION... High pressure center far northeast of Hawaii is very slowly pushing to the northeast. It is pushing so slowly that it will continue to provide the state with the stiff easterly/northeasterly trades winds we have been experiencing. Therefore expect breezy to sometimes windy conditions through tonight and especially through the day Tuesday as the winds pick up speed during the day. AIRMET Tango is in effect for low level turbulence below 6000ft downwind of the mountains. There will be light, passing showers, especially on the windward slopes tonight and Tuesday. So far there has not been enough moisture to warrant an AIRMET for mountain obscuration and that should be the case through Tuesday as well. && .MARINE... Expect moderate to locally strong trades to continue into Thursday, with a decrease beginning on Friday and into the weekend, as the ridge, currently north of the islands, gets nudged eastward and replaced by a front that stalls north and west of the islands. The Small Craft Advisory for the typical near-shore waters around Maui and South of the Big Island, will be lowered around Wednesday night or Thursday. Surf is expected to remain below advisory levels through the week for all shores. There will be a series of small west-northwest to north-northwest swells over the rest of the week. A moderate size northwest swell is slated to arrive late Sunday afternoon, peak Sunday night, followed by a slow drop through Monday night. A series of small south swells will maintain small surf along south facing shores through the period. Surf along east facing shores will hold steady in the small to moderate range through Thursday due to the breezy to locally strong trades, then drop into the weekend as the trade winds become light. && .HFO WATCHES/WARNINGS/ADVISORIES... Small Craft Advisory until 6 PM HST Wednesday for Maalaea Bay- Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters. && $$ DISCUSSION...Powell AVIATION...Chevalier MARINE...Lau