Hilo

Tonight: Mostly clear. Isolated showers in the evening. Haze through the night. Lows 58 to 67 near the shore to 49 to 55 at 4000 feet. Light winds. Chance of rain 20 percent.

Monday: Sunny in the morning, then partly sunny with scattered showers in the afternoon. Haze through the day. Highs around 79 near the shore to around 66 at 4000 feet. Southeast winds up to 10 mph. Chance of rain 50 percent.

Monday Night: Mostly cloudy with scattered showers. Haze. Lows 57 to 67 near the shore to 50 to 57 at 4000 feet. Light winds becoming north up to 15 mph after midnight. Chance of rain 50 percent.

Kona

Tonight: Partly cloudy with isolated showers. Haze. Lows around 69 near the shore to 44 to 51 near 5000 feet. Light winds. Chance of rain 20 percent.

Monday: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Haze through the day. Highs 79 to 84 near the shore to around 65 near 5000 feet. Southwest winds up to 10 mph. 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 67 to 72 near the shore to 46 to 51 near 5000 feet. Light winds. Chance of rain 20 percent.

Waimea

Tonight: Partly cloudy with isolated showers. Haze. Lows 59 to 69 near the shore to 52 to 60 near 3000 feet. Southwest winds up to 10 mph. Chance of rain 20 percent.

Monday: Mostly sunny with isolated showers in the morning, then mostly cloudy with numerous showers in the afternoon. Haze through the day. Highs around 79 near the shore to 69 to 75 near 3000 feet. Southwest winds up to 10 mph shifting to the northwest in the afternoon. Chance of rain 70 percent.

Monday Night: Mostly cloudy. Breezy. Occasional showers in the evening, then numerous showers after midnight. Haze through the night. Lows 59 to 68 near the shore to 52 to 60 near 3000 feet. North winds up to 15 mph shifting to the northeast after midnight. Chance of rain 90 percent.

Kohala

Tonight: Partly cloudy with isolated showers. Haze. Lows 59 to 69 near the shore to 52 to 60 near 3000 feet. Southwest winds up to 10 mph. Chance of rain 20 percent.

Monday: Mostly sunny with isolated showers in the morning, then mostly cloudy with numerous showers in the afternoon. Haze through the day. Highs around 79 near the shore to 69 to 75 near 3000 feet. Southwest winds up to 10 mph shifting to the northwest in the afternoon. Chance of rain 70 percent.

Monday Night: Mostly cloudy. Breezy. Occasional showers in the evening, then numerous showers after midnight. Haze through the night. Lows 59 to 68 near the shore to 52 to 60 near 3000 feet. North winds up to 15 mph shifting to the northeast after midnight. Chance of rain 90 percent.

South Big Island

Tonight: Partly cloudy with isolated showers. Haze. Lows around 71 near the shore to around 51 near 5000 feet. East winds up to 10 mph in the evening becoming light. Chance of rain 20 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 80 near the shore to around 63 near 5000 feet. Southeast winds up to 10 mph. Chance of rain 50 percent.

Monday Night: Partly cloudy. Isolated showers in the evening. Haze through the night. Lows around 72 near the shore to around 53 near 5000 feet. Light winds. Chance of rain 20 percent.

Puna

Tonight: Mostly clear. Isolated showers in the evening. Haze through the night. Lows 58 to 67 near the shore to 49 to 55 at 4000 feet. Light winds. Chance of rain 20 percent.

Monday: Sunny in the morning, then partly sunny with scattered showers in the afternoon. Haze through the day. Highs around 79 near the shore to around 66 at 4000 feet. Southeast winds up to 10 mph. Chance of rain 50 percent.

Monday Night: Mostly cloudy with scattered showers. Haze. Lows 57 to 67 near the shore to 50 to 57 at 4000 feet. Light winds becoming north up to 15 mph after midnight. Chance of rain 50 percent.

Waikoloa

Tonight: Partly cloudy. Isolated showers in the evening, then scattered showers after midnight. Haze through the night. Lows 67 to 73 near the shore to 46 to 52 above 4000 feet. Light winds becoming south up to 10 mph after midnight. Chance of rain 40 percent.

Monday: Mostly sunny with isolated showers in the morning, then mostly cloudy with scattered showers in the afternoon. Haze through the day. Highs 79 to 84 near the shore to 63 to 70 above 4000 feet. Southwest winds up to 10 mph shifting to the northwest in the afternoon. Chance of rain 50 percent.

Monday Night: Mostly cloudy in the evening then becoming partly cloudy. Scattered showers. Haze. Lows around 70 near the shore to 48 to 53 above 4000 feet. Northeast winds up to 15 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Changes are on the way as two fronts will move through the state this week. The first will bring showers and northerly winds tonight into early Monday. Showers should linger Tuesday as the remains of the front move back west over the state. The second front arrives Wednesday night into Thursday, bringing another round of showers and even stronger winds. Pre-frontal winds Wednesday afternoon could be quite gusty. The week should end cool and fairly dry with trades re-established.

Discussion

A few showers have popped up this afternoon on Oahu, but rainfall amounts have been limited to just a few hundredths as the atmosphere remains relatively stable. Otherwise, skies were partly cloudy on most islands and winds were light and out of the south through southwest at most locations.
A cold front is moving toward Kauai County this afternoon, and will move through much the state overnight and early Monday before stalling out near the Big Island late Monday. Moderate to occasionally heavy showers will accompany the front, and winds will become northerly after passage. Tuesday morning low temperatures will be around 5 degrees below normal due to the dry air coming in with the front. By Tuesday afternoon, winds will swing rapidly around to easterly and then southeasterly as the front begins to move back west over the state. Additional showers will form as this occurs.
Wednesday, a new front will approach from the northwest. As the mass field adjusts to an incoming upper level trough, we will have a period of strong south to southwest surface winds over the smaller islands. Gusts of 25 to 35 mph are expected Wednesday afternoon, especially over higher terrain and just downwind (what is normally windward will briefly become leeward during this period of southwest surface winds). Headlines for wind may be needed as we get closer in time. The front is forecast to get to Kauai County around sunset, Oahu in the evening, Maui County before sunrise, and Big Island by noon Thursday. This will bring another round of showers, some possibly strong. Fast movement through the state should limit the risk of flooding.
Friday and Saturday will be cool as relatively dry air moves in behind this second front. Trades will build back in, pushing the remnants of the front south of the state. Showers should be limited as this prevents the moisture from passing back over the state as with the first front earlier in the week.

Aviation

Light background winds have resulted in daytime sea breezes across the island chain again today, increasing cloud cover and producing a few showers over the islands (especially Oahu).
A cold front that is currently to our northwest will arrive across the western end of the state tonight and then progress down the island chain through Monday. Showers are expected along the frontal boundary, with prevailing MVFR conditions as the front moves through. Behind the front, breezy northerly winds will fill in, along with drier conditions.
There are no AIRMETs currently in effect. However, AIRMET Sierra for mountain obscuration will likely be needed this evening and tonight due to increasing clouds and showers, starting on Kauai.

Marine

A strong cold front moves down the island chain from west to east, stalling out near the Big Island by Monday night. By Wednesday an even stronger cold front will quickly move through the islands, spreading strong to near gale force winds across the northwestern coastal waters late next week into Thursday. A Small Craft Advisory remains in effect for coastal waters exposed to the large northwest swell, these elevated combined seas around 10 feet are forecast to linger over waters and channels exposed to this northwest swell energy.
A High Surf Advisory (HSA) is in effect through Monday morning for north and west facing shores exposed to the large northwest swell energy. This swell will hold above HSA thresholds into Monday as yet another much larger overlapping northwest (320-330 degree) swell swiftly builds surf to High Surf Warning (HSW) levels from Monday through Tuesday. We will likely issue an HSW on Monday to cover this next warning level surf event. Yet another XL northwest (320-330 degree) swell will build into the region by Thursday, potentially producing another round of warning level surf along north and west facing shores lasting through Friday. This northwest swell energy will diminish into next weekend.
Surf along east facing shores will remain small through the first half of this week due to a continued disruption in the trade wind flow. Surf heights will remain very small along south facing shores through the forecast period.

HFO Watches/Warnings/Advisories

High Surf Advisory until 6 AM HST Monday for Niihau, Waianae Coast, Oahu North Shore, Maui Windward West, Kauai North, Kauai East, Molokai Windward, Molokai North, Molokai West, Maui Central Valley North, Windward Haleakala.
Small Craft Advisory until 6 PM HST this evening for Kauai Northwest Waters, Kauai Windward Waters, Kauai Leeward Waters, Kauai Channel, Oahu Windward Waters, Kaiwi Channel, Maui County Windward Waters, Alenuihaha Channel, Big Island Windward Waters.

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Data Courtesy of NOAA.gov