Hilo

Tonight: Partly cloudy. Haze in the evening. Scattered showers after midnight. Lows 61 to 69 near the shore to 49 to 54 at 4000 feet. Southwest winds up to 10 mph. Chance of rain 50 percent.

Monday: Partly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 79 near the shore to around 66 at 4000 feet. South winds up to 10 mph shifting to the east around 10 mph in the afternoon. Chance of rain 50 percent.

Monday Night: Partly cloudy. Lows 61 to 67 near the shore to 48 to 54 at 4000 feet. Light winds.

Kona

Tonight: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Haze through the night. Lows around 71 near the shore to 46 to 52 near 5000 feet. Light winds. Chance of rain 50 percent.

Monday: Mostly sunny in the morning then becoming partly sunny. Scattered showers. Haze. Highs 80 to 85 near the shore to around 66 near 5000 feet. Light winds. Chance of rain 50 percent.

Monday Night: Mostly cloudy with isolated showers in the evening, then partly cloudy after midnight. Haze through the night. Lows around 71 near the shore to 46 to 52 near 5000 feet. Light winds. Chance of rain 20 percent.

Waimea

Tonight: Partly cloudy. Isolated showers in the evening. Haze after midnight. Lows 61 to 69 near the shore to 52 to 59 near 3000 feet. East winds up to 10 mph in the evening becoming light. Chance of rain 20 percent.

Monday: Mostly sunny in the morning then becoming partly sunny. Scattered showers. Haze. Highs 73 to 79 near the shore to 67 to 75 near 3000 feet. East winds up to 10 mph. Chance of rain 50 percent.

Monday Night: Partly cloudy. Isolated showers in the evening. Haze in the evening. Lows 60 to 69 near the shore to 52 to 59 near 3000 feet. East winds around 10 mph. Chance of rain 20 percent.

Kohala

Tonight: Partly cloudy. Isolated showers in the evening. Haze after midnight. Lows 61 to 69 near the shore to 52 to 59 near 3000 feet. East winds up to 10 mph in the evening becoming light. Chance of rain 20 percent.

Monday: Mostly sunny in the morning then becoming partly sunny. Scattered showers. Haze. Highs 73 to 79 near the shore to 67 to 75 near 3000 feet. East winds up to 10 mph. Chance of rain 50 percent.

Monday Night: Partly cloudy. Isolated showers in the evening. Haze in the evening. Lows 60 to 69 near the shore to 52 to 59 near 3000 feet. East winds around 10 mph. Chance of rain 20 percent.

South Big Island

Tonight: Mostly clear. Isolated showers in the evening. Haze through the night. Lows around 71 near the shore to around 50 near 5000 feet. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Monday: Mostly sunny in the morning then becoming partly sunny. Scattered showers. Haze. Highs around 83 near the shore to around 63 near 5000 feet. East winds 10 to 15 mph. Chance of rain 40 percent.

Monday Night: Mostly cloudy with isolated showers in the evening, then partly cloudy after midnight. Haze through the night. Lows around 71 near the shore to around 51 near 5000 feet. East winds up to 10 mph. Chance of rain 20 percent.

Puna

Tonight: Partly cloudy. Haze in the evening. Scattered showers after midnight. Lows 61 to 69 near the shore to 49 to 54 at 4000 feet. Southwest winds up to 10 mph. Chance of rain 50 percent.

Monday: Partly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 79 near the shore to around 66 at 4000 feet. South winds up to 10 mph shifting to the east around 10 mph in the afternoon. Chance of rain 50 percent.

Monday Night: Partly cloudy. Lows 61 to 67 near the shore to 48 to 54 at 4000 feet. Light winds.

Waikoloa

Tonight: Partly cloudy. Scattered showers in the evening. Haze through the night. Lows around 71 near the shore to 49 to 54 above 4000 feet. Light winds. Chance of rain 40 percent.

Monday: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Haze through the day. Highs around 83 near the shore to 64 to 70 above 4000 feet. South winds up to 10 mph shifting to the northwest around 10 mph in the afternoon. Chance of rain 50 percent.

Monday Night: Partly cloudy. Isolated showers in the evening. Haze in the evening. Lows around 71 near the shore to 48 to 53 above 4000 feet. Light winds. Chance of rain 20 percent.

Detailed Forecast

Synopsis

A trough northwest of Kauai will maintain a ridge over the islands resulting in minimal shower activity and light southeasterly winds. Another front will approach and stall northwest of Kauai on Tuesday, bringing clouds and showers to the western end of the island chain Wednesday. More typical trade wind weather with showers favoring windward and mountain areas will become reestablished Thursday into the weekend.

Discussion

The forecast has been updated to reflect the latest National Blend of Models (NBM), but the changes are minimal. There remains good agreement with the models in the short term, but significant differences in the ECMWF and GFS global models Wednesday onwards.
A surface and upper level ridge over the islands is maintaining light southeasterly flow with a stable airmass in place. This results is localized land and sea breezes and minimal shower activity. The surface ridge has been pushed over the islands due to a trough to the northwest which is expected to weaken and be pushed to the northeast by another front currently far to the northwest of the main Hawaiian islands.
The GFS and ECMWF are in good agreement with this next front approaching from the northwest Tuesday. Both models bring pre- frontal convergence bands to the northwest of Kauai Tuesday night. The GFS stalls the front to the northwest of Kauai, while the ECMWF brings the front over the Garden Isle, with additional moisture being drawn northward over the Oahu and parts of Maui County. For now the forecasts falls more in line with the GFS in keeping the bulk of the shower activity west of Kauai.
The global models have some significant differences during the second half of the week. Both models show the front dying and being replaced by a surface trough. The GFS goes on to form a low pressure system along the trough, west of the islands, with the low moving to the west. The GFS also develops a strong upper level low in conjunction with the surface feature. The ECMWF is slower to develop a low along the trough, and when it does so, it develops one north of the islands that lifts northward. While the models show significant differences during the second half of the week, they remain in decent agreement with a ridge north of the islands allowing trade winds to build back in over the islands. Accompanying the trades would be showers focused over the windward and mountains areas.
The upper level feature from the GFS could spell increased winds over the Big Island Summits Thursday on through the weekend. Currently the forecast keeps winds below advisory levels for the summits, however will have to watch future model runs to see how things may play out.

Aviation

Light southeasterly flow will continue through the forecast period with local sea breezes during the day and land breezes at night. VFR conditions expected through Monday under a relatively dry and stable air mass.
No AIRMETs are in effect and none are expected.

Marine

Ridging will remain in place over the area for the first half of the week, maintaining light to moderate southeast background winds. This pattern will allow for daytime sea breezes and nighttime land breezes along waters adjacent to the coasts. Meanwhile, an extra large northwest swell that peaked Sunday morning will decline over the next day or so, but will produce seas above Small Craft Advisory (SCA) levels for exposed waters through midday on Monday. A Small Craft Advisory remains in effect until that time, but seas will quickly fall below SCA levels Monday afternoon into Monday night as the swell continues to fade. On Wednesday, a front will approach Kauai from the northwest, but guidance continues to indicate that it will weaken and then retreat back to the west during the latter part of the week. Easterly trade winds will finally return Friday into the weekend as surface high pressure builds northeast of the area.
The current, extra-large, long-period northwest (310-320 degree) swell peaked earlier Sunday and will slowly decline tonight through Monday. With that said, as of Sunday afternoon the Waimea Bay buoy 51201 continues to report impressive northwest swell energy at 12-15 feet, 17 seconds. This swell is expected to slowly lose energy tonight, but it will continue to produce warning level surf throughout the night and into early Monday. Therefore, the High Surf Warning remains in effect through noon on Monday for exposed north and west facing shores of most islands. Surf is then expected to drop to advisory levels by Monday afternoon as the swell energy eases. Another large, long period northwest swell (310-330 degree) is forecast to fill in on Wednesday, peak Thursday, then slowly subside on Friday. Surf may once again approach warning levels.
East shore surf will remain small through the weekend due to weak winds. Some south facing shores experienced a small amount of westerly wrap from this weekend's large northwest swell on Sunday, but this will ease by Monday and south shore surf will remain small throughout the next few days.

Fire weather

Rather dry conditions are expected to persist through Tuesday. Winds will be light and variable under a stable land and sea breeze pattern, preventing critical fire weather thresholds from being approached. With the inversion holding around 6,500 ft, very dry conditions will persist on the upper elevations of the Big Island and Maui.

HFO Watches/Warnings/Advisories

High Surf Warning until noon HST Monday for Niihau, Kauai Leeward, Waianae Coast, Oahu North Shore, Maui Windward West, Kona, Kohala, Kauai North, Molokai Windward, Molokai North, Molokai West, Maui Central Valley North, Windward Haleakala.
Small Craft Advisory until noon HST Monday for Kauai Northwest Waters, Kauai Windward Waters, Kauai Leeward Waters, Kauai Channel, Oahu Windward Waters, Oahu Leeward Waters, Kaiwi Channel, Maui County Windward Waters, Alenuihaha Channel, Big Island Windward Waters.

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Data Courtesy of NOAA.gov