981 FXHW60 PHFO 050202 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 402 PM HST Thu Apr 4 2019 .SYNOPSIS... Trade winds will weaken tonight and become light and variable over the next couple of days. Dry and stable conditions will prevail. A weak cold front will over Kauai by Sunday, then stall and weaken over the state bringing an increase in rain chances. An upper level system will develop near the islands Tuesday and may bring active weather to the area towards the middle and end of next week. && .DISCUSSION... An eastward tracking 1024 mb high centered about 600 miles northeast of Hawaii this afternoon. The high is driving moderate to locally fresh trade winds across the state. Ridging aloft over the area is keeping atmospheric conditions stable. 00Z soundings at Hilo and Lihue this afternoon show a strong inversion at 4 kft with precipitable water values below normal at 0.8 inches. With dry and stable conditions prevailing, mostly sunny skies were present across the state today. As the high moves away over the next couple of days, a cold front will approach from the northwest. Trade winds will weaken tonight as the pressure gradient relaxes, with winds becoming light and variable Friday and Saturday. Daytime sea breezes and nighttime land breezes will set up over all islands and bring some interior clouds during the day and clearing at night. The relatively dry air at the surface will not likely result in many showers developing over the islands through the day Saturday. The weak front is expected to reach Kauai Sunday, then stall and dissipate over the islands early next week. High pressure will fill in behind the front and gradually build in trade winds starting Sunday, becoming moderate to fresh winds around Monday night or Tuesday. The trades will focus most of the precipitation along and ahead of the front over the windward and mauka areas. Both the GFS and ECMWF also show a small pre-frontal band forming near the Big Island on Sunday and sliding northward into Monday. In short, somewhat wetter weather, especially for the windward sides, is expected Sunday into Monday. Meanwhile, a digging upper level trough will develop just north of the islands around Monday, then shift east of the area on Tuesday as it forms a cutoff low. This trough is expected to tap into the some of the moisture left over from the front upstream of Hawaii and produce enhanced trade wind showers from Tuesday through the end of the work week. The location and timing of this feature is not consistent between the models during the middle and latter portions of next week. We will continue to monitor the trends as time gets closer, but a bit too early to narrow down details at this point. && .AVIATION... Surface high pressure just north-northwest of Hawaii will generate somewhat breezy easterly trade winds this afternoon. The winds should gradually decrease tonight into Friday. Mostly dry conditions across the state with isolated showers possible on the windward slopes. These windward showers may generate isolated, very brief periods of MVFR conditions for these areas, otherwise VFR conditions are expected for the rest of the state. No AIRMETS are currently in effect. && .MARINE... The moderate to locally strong trade winds today are slow to diminish, so the Small Craft Advisory (SCA) has been extended through tonight for the waters around Maui and the Big Island. The trades will shift to the east-southeast and ease to light and variable by Saturday as the ridge north of Kauai weakens and shifts south ahead of an advancing front. While models differ on the eventual position and strength of the front, a new high building in behind it will increase northeast to east trades again later Saturday night through early next week. The current northwest swell will continue to lower tonight as a reinforcing northwest swell spreads southeast across the state, keeping surf heights slightly elevated. However, a new long- period, north-northwest swell arriving Friday may cause surf to approach the High Surf Advisory criteria starting late Friday. This swell will gradually lower Saturday ahead of another northwest swell arriving late Saturday night, which could boost surf heights back to near- advisory level Sunday, before gradually lowering early next week. The latest guidance suggests there may be a slight boost in surf heights along east facing shores starting next Tuesday or Wednesday as trades strengthen. No other significant swells are expected through the period. && .HFO WATCHES/WARNINGS/ADVISORIES... Small Craft Advisory until 6 AM HST Friday for Maalaea Bay- Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters. && $$ DISCUSSION...Foster AVIATION...Chevalier MARINE...TS