West Side

Today: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 75 to 80. East winds up to 10 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 40 percent.

Tonight: Partly cloudy with isolated showers. Lows 64 to 71. East winds 10 to 15 mph. Chance of rain 20 percent.

Sunday: Mostly sunny with scattered showers. Haze in the afternoon. Highs 75 to 81. East winds 10 to 15 mph. Chance of rain 40 percent.

South Side

Today: Mostly sunny. Haze in the morning. Isolated showers in the morning, then scattered showers in the afternoon. Highs around 83. Northeast winds 10 to 15 mph. Chance of rain 30 percent.

Tonight: Partly cloudy with isolated showers. Lows 62 to 73. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Sunday: Mostly sunny with isolated showers. Haze in the afternoon. Highs around 83. East winds 10 to 15 mph. Chance of rain 20 percent.

North Shore

Today: Mostly cloudy. Scattered showers in the morning, then numerous showers in the afternoon. Highs around 78 near the shore to around 64 near 5000 feet. East winds 10 to 15 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy. Numerous showers and slight chance of thunderstorms in the evening, then occasional showers and slight chance of thunderstorms after midnight. Lows around 66 near the shore to around 49 near 5000 feet. East winds 10 to 15 mph. Chance of rain 90 percent.

Sunday: Mostly cloudy. Occasional showers in the morning, then numerous showers in the afternoon. Haze in the afternoon. Highs 75 to 80 near the shore to around 64 near 5000 feet. East winds 10 to 15 mph. Chance of rain 80 percent.

Central Maui

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Upcountry

Today: Mostly sunny in the morning then becoming partly sunny. Scattered showers. Haze through the day. Highs 53 to 65. East winds around 10 mph. Chance of rain 50 percent.

Tonight: Partly cloudy with scattered showers and slight chance of thunderstorms. Haze. Lows around 44 at the visitor center to around 38 at the summit. East winds 10 to 15 mph. Chance of rain 50 percent.

Sunday: Mostly sunny with scattered showers. Haze. Highs 54 to 65. East winds 10 to 15 mph. Chance of rain 50 percent.

East Maui

Today: Mostly cloudy. Scattered showers in the morning, then numerous showers in the afternoon. Highs around 78 near the shore to around 64 near 5000 feet. East winds 10 to 15 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy. Numerous showers and slight chance of thunderstorms in the evening, then occasional showers and slight chance of thunderstorms after midnight. Lows around 66 near the shore to around 49 near 5000 feet. East winds 10 to 15 mph. Chance of rain 90 percent.

Sunday: Mostly cloudy. Occasional showers in the morning, then numerous showers in the afternoon. Haze in the afternoon. Highs 75 to 80 near the shore to around 64 near 5000 feet. East winds 10 to 15 mph. Chance of rain 80 percent.

Lanai City

Today: Mostly sunny. Isolated showers in the afternoon. Haze in the afternoon. Highs 70 to 78. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Tonight: Mostly clear. Isolated showers in the evening. Lows 60 to 65. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Sunday: Mostly sunny with isolated showers. Haze through the day. Highs 71 to 78. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Kaunakakai

Today: Mostly sunny with isolated showers. Haze in the afternoon. Highs 67 to 83. East winds 10 to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Scattered showers in the evening, then isolated showers after midnight. Lows 54 to 71. East winds 10 to 15 mph. Chance of rain 40 percent.

Sunday: Breezy. Mostly sunny with scattered showers. Haze. Highs 67 to 83. East winds 10 to 20 mph. Chance of rain 40 percent.

Detailed Forecast

Synopsis

Winds will continue to weaken and shift to the east to southeast today, as moisture near the state increases and the atmosphere destabilizes. Showers, some potentially heavy, will increase over windward slopes, while leeward areas experience periods of afternoon showers through at least Sunday. Trade winds will return Tuesday or Wednesday.

Discussion

No changes to the short term grids, and the only changes for day 3 onwards was to nudge towards the latest run of the National Blend of Models.
No change in the forecast philosophy this morning. The high pressure northeast of the state continues to weaken and move to the east. Combined with a surface low to the west of Kauai winds over the islands are weakening, and shifting to the east to southeast. We are already seeing that directional shift in the low clouds near the islands, and we can expect that to become more widespread across the region today.
An upper level low just north of the islands, combined with the upper level trough associated with the surface low west of the islands, will provide instability over the coming days. A nearby band of moisture will likely move into the islands from the east. Convergent east-southeasterly flow on the mid-level trough's northern flank will produce an increase in moisture, raising precipitable water, from its current value of around an inch, to 1.3 to 1.5 inches.
Guidance has been showing the deepest moisture developing just north of the islands this weekend. However, there will be enough moisture and instability to increase shower frequency and intensity over windward slopes of all islands. With the weaker winds, afternoon sea breezes will produce clouds and showers over some leeward areas. Some showers may be heavy, and an isolated rumble of thunderstorm cannot be ruled out, however the greatest chance from thunderstorms appears to remain north of the coastal waters. The ingredients still do not push confidence high enough for the issuance of a Flood Watch, though the situation will need monitoring.
The GFS and ECMWF show the chances for rainfall declining by late Sunday or Monday. The upper-level trough over the region will weaken, and the mid-level trough will lift northward, lowering chances for rainfall. The main difference between the models is the strength of the east-southeast winds, which are stronger in the GFS due to a more rapid weakening of the nearby surface low.
A gradual return to a more stable trade wind flow is expected Tuesday or Wednesday.

Aviation

Light to moderate trade winds will continue to weaken through the remainder of today and shift out of the east- southeast. Thus, expect isolated to scattered showers to affect mainly windward areas this morning. By this afternoon, however, localized sea breezes may lead to the development of isolated to scattered showers over leeward locations as well. Brief MVFR ceilings and visibility will be possible in some of the heavier showers.
Enough instability will be present this evening and tonight to introduce a slight chance of thunderstorms to windward portions of the smaller islands.
No AIRMETs are in effect.

Marine

Fresh to moderate trades will hold through today before veering slightly east southeast over the western half of the state as an area of low pressure meanders northwest of the state Sunday into early next week. A few isolated thunderstorms will be possible today into Sunday due to the proximity of the low. The low is expected to gradually weaken Sunday as a strong high passes north of state which may generate moderate to locally strong easterly winds over the eastern half of the state, requiring a Small Craft Advisory (SCA). The western half of the state will remain in moderate to locally fresh east southeast flow. The area of low pressure is expected gradually drift west and weaken early next week, allowing winds to shift back to a more typical easterly direction. Fresh to locally strong trades are expected to return statewide by Tuesday night and hold through the second half of next week.
A moderate, west northwest (300-320) swell has peaked and has been trending down overnight trend down through the weekend. The High Surf Advisory has been cancelled as surf heights have dropped below advisory levels. A small to moderate, medium period north northwest swell (340-350) may overlap the fading west northwest swell Sunday night into Monday. In the long range, a series of small, long period northwest swell look to keep surf from going flat through much of next week.
Rough choppy surf along east facing shores will drop a notch today and hold into early next week. As winds strengthen by mid week can expect east facing shore surf to pick back up a couple of notches.

HFO Watches/Warnings/Advisories

None.

Data Courtesy of NOAA.gov