Hilo

Tonight: Mostly cloudy with numerous showers. Lows 65 to 71 near the shore to 54 to 59 at 4000 feet. Southeast winds up to 10 mph shifting to the north after midnight. Chance of rain 70 percent.

Tuesday: Cloudy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 79 to 85 near the shore to 65 to 70 at 4000 feet. East winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 70 percent.

Tuesday Night: Cloudy. Numerous showers in the evening, then showers after midnight. Lows 62 to 70 near the shore to 52 to 57 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 80 percent.

Kona

Tonight: Partly cloudy with isolated showers. Lows around 74 near the shore to 49 to 54 near 5000 feet. Light winds. Chance of rain 20 percent.

Tuesday: Mostly sunny in the morning, then mostly cloudy with scattered showers in the afternoon. Highs 85 to 90 near the shore to around 69 near 5000 feet. West winds up to 10 mph. Chance of rain 40 percent.

Tuesday Night: Mostly cloudy in the evening then becoming partly cloudy. Isolated showers. Lows 70 to 75 near the shore to 47 to 52 near 5000 feet. North winds up to 10 mph. Chance of rain 20 percent.

Waimea

Tonight: Mostly cloudy. Breezy. Scattered showers in the evening, then numerous showers after midnight. Lows 65 to 72 near the shore to 57 to 63 near 3000 feet. East winds up to 20 mph. Chance of rain 70 percent.

Tuesday: Breezy. Mostly cloudy with scattered showers. Highs 65 to 86. East winds up to 25 mph increasing to 10 to 25 mph in the afternoon. Chance of rain 50 percent.

Tuesday Night: Breezy. Mostly cloudy with scattered showers. Lows 63 to 71 near the shore to 55 to 62 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Kohala

Tonight: Mostly cloudy. Breezy. Scattered showers in the evening, then numerous showers after midnight. Lows 65 to 72 near the shore to 57 to 63 near 3000 feet. East winds up to 20 mph. Chance of rain 70 percent.

Tuesday: Breezy. Mostly cloudy with scattered showers. Highs 65 to 86. East winds up to 25 mph increasing to 10 to 25 mph in the afternoon. Chance of rain 50 percent.

Tuesday Night: Breezy. Mostly cloudy with scattered showers. Lows 63 to 71 near the shore to 55 to 62 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

South Big Island

Tonight: Partly cloudy. Breezy. Isolated showers in the evening. Lows around 75 near the shore to around 52 near 5000 feet. East winds 10 to 20 mph. Chance of rain 20 percent.

Tuesday: Breezy. Mostly sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs around 86 near the shore to around 69 near 5000 feet. East winds 10 to 25 mph. Chance of rain 20 percent.

Tuesday Night: Partly cloudy. Breezy. Isolated showers in the evening. Lows around 74 near the shore to around 51 near 5000 feet. East winds 15 to 25 mph. Chance of rain 20 percent.

Puna

Tonight: Mostly cloudy with numerous showers. Lows 65 to 71 near the shore to 54 to 59 at 4000 feet. Southeast winds up to 10 mph shifting to the north after midnight. Chance of rain 70 percent.

Tuesday: Cloudy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 79 to 85 near the shore to 65 to 70 at 4000 feet. East winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 70 percent.

Tuesday Night: Cloudy. Numerous showers in the evening, then showers after midnight. Lows 62 to 70 near the shore to 52 to 57 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 80 percent.

Waikoloa

Tonight: Partly cloudy with isolated showers. Lows around 75 near the shore to 51 to 56 above 4000 feet. Light winds becoming east up to 10 mph after midnight. Chance of rain 20 percent.

Tuesday: Sunny in the morning then becoming partly sunny. Breezy. Highs 84 to 91 near the shore to 67 to 74 above 4000 feet. Northeast winds up to 20 mph.

Tuesday Night: Partly cloudy. Isolated showers in the evening. Lows around 73 near the shore to 50 to 55 above 4000 feet. East winds up to 10 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

A weak low level trough moving westward across the region will bring enhanced trade wind showers to parts of the state through this evening. In its wake, trades will strengthen slightly to become moderate to breezy with drier conditions expected through Wednesday. An uptick in showers will be possible from Thursday into Saturday as another weak disturbance moves through the island chain.

Discussion

Satellite imagery and radar continue to show bands of unstable cumulus and showers moving across the island chain this afternoon in association with a low level trough moving westward across the state. While these showers are primarily focusing over windward and mauka areas, some showers are still circumnavigating the terrain into leeward areas as well. This is particularly true for leeward Oahu this afternoon as showers stream into the area along a convergent line extending from Molokai. Looking upstream of the island chain, drier air should filter in sometime this evening from east to west across the state in the wake of the trough and the surface ridge to the northwest of the state will strengthen slightly. This pattern will help to limit shower activity and strengthen the trades to become moderate to breezy through mid week.
Another plume of tropical moisture and a weak low level trough will move into the eastern end of the state on Thursday and bring another band of tropical moisture across the area. Shower chances will increase as this low level disturbance moves through, with current model guidance concentrating most of the shower activity across windward Big Island for that period. At the same time, an upper level low will approach from the east and bring some added instability to the trades, but model guidance suggests that the low itself will not reach the state. Expect a slight decrease in trade winds heading into the weekend as the trough weakens the ridge. This slightly weaker wind pattern may allow for the development of daytime sea breezes along western terrain sheltered slopes from Friday into the weekend.

Aviation

A plume of moisture moving through the state will enhance the trade wind showers with brief MVFR conditions possible with any showers through tonight. A drier air mass should move in late tonight with breezy and dry trade wind weather expected for Tuesday.
AIRMET Sierra remains in effect for Kauai, Oahu and windward Big Island due to low clouds and showers. A decrease of showers is expected later tonight.

Marine

Fresh trade winds will continue through Thursday before weakening on Friday. A Small Craft Advisory (SCA) is in effect for the windier waters and channels around Maui County and the Big Island through Tuesday. Some or all of these zones will likely continue into Thursday as winds remain breezy.
The current moderate to large, medium to long period north swell will peak this evening and slowly decline through the end of the week. A High Surf Advisory (HSA) is in effect through Tuesday for all north facing shores across the state. Surf along west facing shores will remain slightly elevated with the influence of the north swell through Tuesday. East facing shore wind waves will gradually pick up Tuesday in response to strengthening trades and remain rough and choppy through the rest of the week. Areas exposed to the north swell on the east shores will also see a wrap with this swell. Surf along south facing shores looks to remain small with background southerly swells.

HFO Watches/Warnings/Advisories

High Surf Advisory until 6 PM HST Tuesday for Niihau, Oahu North Shore, Olomana, Maui Windward West, Kauai North, Kauai East, Koolau Windward, Molokai Windward, Molokai North, Maui Central Valley North, Windward Haleakala, Big Island East, Big Island North.
Small Craft Advisory until 6 PM HST Tuesday for Maui County Windward Waters, Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Windward Waters, Big Island Leeward Waters, Big Island Southeast Waters.

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Data Courtesy of NOAA.gov