Today: Partly sunny with scattered showers. Highs 76 to 82 near the shore to 63 to 70 at 4000 feet. North winds up to 15 mph. Chance of rain 40 percent.
Tonight: Breezy. Mostly cloudy with showers. Lows 60 to 69 near the shore to 51 to 56 at 4000 feet. North winds up to 20 mph. Chance of rain 80 percent.
Monday: Showers and isolated thunderstorms. Locally heavy rainfall possible. Highs 73 to 80 near the shore to 60 to 67 at 4000 feet. North winds 10 to 15 mph. Chance of rain near 100 percent.
Kona
Today: Mostly sunny. Scattered showers in the afternoon. Highs 81 to 86 near the shore to around 67 near 5000 feet. Light winds. Chance of rain 30 percent.
Tonight: Partly cloudy. Isolated showers in the evening. Lows 67 to 72 near the shore to 45 to 53 near 5000 feet. Light winds. Chance of rain 20 percent.
ARTICLE CONTINUES BELOW AD
ARTICLE CONTINUES BELOW AD
Monday: Sunny in the morning, then partly sunny with scattered showers and isolated thunderstorms in the afternoon. Locally heavy rainfall possible in the afternoon. Highs 79 to 85 near the shore to around 65 near 5000 feet. Light winds. Chance of rain 50 percent.
Waimea
Today: Mostly sunny in the morning then becoming partly sunny. Breezy. Scattered showers. Highs 63 to 82. East winds 10 to 25 mph. Chance of rain 40 percent.
Tonight: Windy. Mostly cloudy with showers. Lows 59 to 66 near the shore to 52 to 60 near 3000 feet. East winds 10 to 20 mph. Chance of rain 80 percent.
Monday: Mostly cloudy. Breezy. Numerous showers and isolated thunderstorms in the morning, then scattered showers and isolated thunderstorms in the afternoon. Locally heavy rainfall possible. Highs 60 to 80. Northeast winds 10 to 20 mph. Chance of rain 70 percent.
Kohala
Today: Mostly sunny in the morning then becoming partly sunny. Breezy. Scattered showers. Highs 63 to 82. East winds 10 to 25 mph. Chance of rain 40 percent.
ARTICLE CONTINUES BELOW AD
Tonight: Windy. Mostly cloudy with showers. Lows 59 to 66 near the shore to 52 to 60 near 3000 feet. East winds 10 to 20 mph. Chance of rain 80 percent.
Monday: Mostly cloudy. Breezy. Numerous showers and isolated thunderstorms in the morning, then scattered showers and isolated thunderstorms in the afternoon. Locally heavy rainfall possible. Highs 60 to 80. Northeast winds 10 to 20 mph. Chance of rain 70 percent.
South Big Island
Today: Mostly sunny. Scattered showers in the afternoon. Highs around 82 near the shore to around 67 near 5000 feet. East winds up to 15 mph. Chance of rain 30 percent.
Tonight: Partly cloudy. Isolated showers in the evening. Lows around 70 near the shore to around 50 near 5000 feet. Northeast winds up to 10 mph in the evening becoming light. Chance of rain 20 percent.
Monday: Sunny in the morning, then partly sunny with scattered showers and isolated thunderstorms in the afternoon. Locally heavy rainfall possible in the afternoon. Highs around 81 near the shore to around 65 near 5000 feet. Light winds. Chance of rain 40 percent.
Puna
ARTICLE CONTINUES BELOW AD
Today: Partly sunny with scattered showers. Highs 76 to 82 near the shore to 63 to 70 at 4000 feet. North winds up to 15 mph. Chance of rain 40 percent.
Tonight: Breezy. Mostly cloudy with showers. Lows 60 to 69 near the shore to 51 to 56 at 4000 feet. North winds up to 20 mph. Chance of rain 80 percent.
Monday: Showers and isolated thunderstorms. Locally heavy rainfall possible. Highs 73 to 80 near the shore to 60 to 67 at 4000 feet. North winds 10 to 15 mph. Chance of rain near 100 percent.
Waikoloa
Today: Sunny and breezy. Highs 81 to 87 near the shore to 65 to 71 above 4000 feet. Northeast winds up to 25 mph.
Tonight: Mostly clear. Breezy. Lows around 70 near the shore to 45 to 53 above 4000 feet. East winds up to 25 mph with gusts to 45 mph.
Monday: Mostly sunny. Isolated thunderstorms in the morning, then isolated showers and thunderstorms in the afternoon. Locally heavy rainfall possible in the afternoon. Highs 79 to 86 near the shore to 64 to 69 above 4000 feet. North winds 15 TO 25 mph. Chance of rain 20 percent.
Detailed Forecast
Synopsis
A weakening cold front just north of the islands will stall north of Kauai as the high pressure ridge builds in over the region today. Trade wind speeds will increase across the state through Monday. Bands of low clouds northeast of the island chain will enhance shower activity today, favoring windward and mountain areas. An unstable upper low developing northeast of Oahu will drift into the eastern islands from Sunday night through Tuesday. Periods of heavy showers and isolated thunderstorms are forecast over Maui and Hawaii Counties. Enhanced shower trends will spread westward over all islands from Monday night through Wednesday. Another stronger cold front moves into the islands by Friday with another round of wet unstable weather forecast statewide, increasing the potential for periods of heavy rainfall lasting into next weekend.
Discussion
The satellite image this morning shows a weak cold front stalling out roughly 150 miles north of Kauai. Several bands of clouds northeast of the state will keep showers in the forecast this morning, favoring windward and mountain areas. Local radar imagery shows scattered to numerous showers drifting into each island on the strengthening trade winds. Water vapor satellite imagery shows an upper level low deepening just north of the Big Island. This upper low will enhance showers statewide on Monday and Tuesday.
The persistent dry weather pattern will end this week with opportunities for enhanced rainfall and possible thunderstorms across the islands. A weakening cold front will stall just north of Kauai today as the high pressure ridge builds into the region. Increasing trade winds into the moderate to locally breezy range are expected starting today and lasting through Monday. Trade winds will decrease to moderate levels on Tuesday and Wednesday, becoming a light wind pattern from Thursday through early Friday. A pocket of cold air north of the Big Island will produce an unstable upper low later today. This low will then drift into the Big Island and Maui from late Sunday into Monday increasing rainfall activity with the periods of heavy rain and isolated thunderstorms across the eastern half of the state. Thunderstorm coverage was expanded this morning to include Maui and Hawaii Counties from Monday to Tuesday.
Strong winds associated with this approaching upper low will move into highest mountain peaks of the Big Island later tonight through Monday afternoon. Wind speeds from 50 to 60 MPH with higher gusts are expected. A High Wind Watch was issued for these strong winds over the summits of Mauna Kea and Mauna Loa on the Big Island. Colder air near the center of this upper low will also bring unstable showers with snow levels dropping to around 12,000 feet elevation over the eastern half of the state. Expect periods of snow showers over the peaks of Mauna Kea and Mauna Loa into Wednesday.
The medium range forecast guidance shows this upper low weakening and drifting westward on Tuesday and Wednesday, spreading enhanced rainfall to all islands. Rainfall amounts in this trade wind pattern will tend to favor windward and mountain areas, however the instability with this upper low will lift the trade wind inversion heights just enough for some showers to drift into typically drier leeward areas. The upper low will lift northward on Thursday with a brief decrease in the shower activity.
Trade wind speeds will decrease from Wednesday to Thursday as the high pressure ridge north of the islands weakens in response to another cold front approaching the islands from the northwest. Long range weather models continue to show a strong upper low in the far North Pacific diving southward towards Hawaii. If this low tracks as predicted, the upper level system will merge with the surface cold front increasing the potential for another round of heavy rain across the state from Friday into next weekend. However, island by island rainfall impacts are highly dependent on the track of this upper level cold core low. Even slight deviations on the path of the low center as it moves towards the Hawaiian Islands will create large changes to the expected weather conditions. Stay tuned as the forecast and rainfall impacts for Friday into next weekend will likely evolve over time.
Aviation
A ridge of high pressure to the north and west of the State will orient low level flow to be out of the north. A weak front dissipating well north of the islands will serve as a low level moisture source. Bands of clouds and weak showers will favor north and northeast facing slopes and coasts. A weak eddy to the lee of the Big Island will keep south and west facing coasts of the Big Island in and out of cloud cover.
AIRMET Sierra for Mountain obscuration is in effect for Oahu. Conditions are expected to end by late morning. Elsewhere, MVFR conditions should remain localized. VFR conditions will prevail most areas of the state through late afternoon.
Beginning this evening, a sharp upper level trough will move in from west. This is expected to enhance shower activity statewide. Mountain obscuration will likely become a concern once again, starting late this evening or early Monday.
AIRMET Tango for moderate upper level turbulence has been reissued due to the approach of the upper level trough. Conditions are expected to persist through at least late afternoon.
Marine
Northeasterly trade winds will be trending stronger today, as high pressure passes far N of the area, and a surface trough sharpens several hundred miles NE of the islands. Guidance indicates a further sharpening of the trough leading to a bit of a surge in NE winds tonight, especially over the W end of the island chain. A Small Craft Advisory (SCA) now posted for the windier zones around Maui and the Big Island will expand to include nearly all other zones by tonight, and may need to be extended in time beyond Monday afternoon.
The high will move far NE of the area late Monday and Tuesday as the surface trough moves over the islands from the E, and then moves W of the islands. This will shift winds to an E to SE direction, and may lead to some weakening as well, dependent on the evolution of the trough. The trough will likely bring an increase in showers, some locally heavy, with what appears to be an increasing potential for thunderstorms, especially over the eastern waters, as the atmosphere destabilizes in response to a nearby low aloft. General expectation is that the trough will either dissipate, or be W of the area, by mid-week, with E to SE winds over the entire area. The weakening low aloft will linger over the state, continuing to fuel the potential for increased showers, some potentially heavy.
Surf will be below advisory levels along all shores for at least the next couple of days. Long-period forerunners (17-21 seconds) associated with a new NW swell have been gradually increasing in magnitude at buoys 51001/51101 NW of Kauai over the past couple of hours, thus an upward trend in surf along exposed N and W shores can be expected later today into tonight as this swell moves through island waters. A peak is expected early Monday, with a mix of relatively small N and NW swells then prevailing until the end of the week, when the potential for a very large NNW swell increases. Although confidence in this outcome is low, forecast models have been showing some run-to-run consistency over the last couple of days. An increase in trade wind swell is expected the next couple of days as trades increase near and upstream of the islands.
HFO Watches/Warnings/Advisories
High Wind Watch from this evening through Monday afternoon for Big Island Summits.
Small Craft Advisory until 6 PM HST Monday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.
Small Craft Advisory from 6 PM this evening to 6 PM 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, Maui County Leeward Waters.
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