Photo Credit: Tyler Rooke

West Side

Today: Breezy. Mostly cloudy with scattered showers and slight chance of thunderstorms in the morning, then mostly sunny with scattered showers in the afternoon. Highs 79 to 86. Northeast winds 15 to 25 mph. Chance of rain 50 percent.

Tonight: Partly cloudy with scattered showers. Lows 65 to 71. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Monday: Mostly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 79 to 86. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

South Side

Today: Breezy. Mostly cloudy with slight chance of thunderstorms and isolated showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs around 85. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Tonight: Mostly clear. Breezy. Lows 63 to 71. North winds 10 to 20 mph.

Monday: Sunny and breezy. Highs around 85. North winds 10 to 20 mph.

North Shore

Today: Breezy. Frequent showers and slight chance of thunderstorms in the morning, then frequent showers in the afternoon. Highs 76 to 82 near the shore to around 62 near 5000 feet. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain near 100 percent.

Tonight: Frequent showers. Lows around 67 near the shore to 46 to 53 near 5000 feet. East winds 10 to 15 mph. Chance of rain near 100 percent.

Monday: Frequent showers in the morning, then scattered showers in the afternoon. Highs 76 to 82 near the shore to around 62 near 5000 feet. East winds 10 to 15 mph. Chance of rain near 100 percent.

Central Maui

Today: Breezy. Mostly cloudy with slight chance of thunderstorms and isolated showers in the morning, then mostly sunny with scattered showers in the afternoon. Highs 81 to 86. Northeast winds 10 to 20 mph. Chance of rain 40 percent.

Tonight: Partly cloudy with isolated showers. Lows 63 to 69. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Monday: Mostly sunny. Isolated showers in the morning. Highs 81 to 86. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Upcountry

Today: Cloudy with scattered showers and slight chance of thunderstorms in the morning, then partly sunny with scattered showers in the afternoon. Highs around 56 at the visitor center to around 53 at the summit. East winds up to 10 mph. Chance of rain 50 percent.

Tonight: Partly cloudy with scattered showers. Lows around 45 at the visitor center to around 41 at the summit. East winds 10 to 15 mph. Chance of rain 50 percent.

Monday: Mostly sunny in the morning then becoming partly sunny. Scattered showers. Highs around 56 at the visitor center to around 53 at the summit. East winds around 10 mph. Chance of rain 50 percent.

East Maui

Today: Breezy. Frequent showers and slight chance of thunderstorms in the morning, then frequent showers in the afternoon. Highs 76 to 82 near the shore to around 62 near 5000 feet. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain near 100 percent.

Tonight: Frequent showers. Lows around 67 near the shore to 46 to 53 near 5000 feet. East winds 10 to 15 mph. Chance of rain near 100 percent.

Monday: Frequent showers in the morning, then scattered showers in the afternoon. Highs 76 to 82 near the shore to around 62 near 5000 feet. East winds 10 to 15 mph. Chance of rain near 100 percent.

Lanai City

Today: Mostly cloudy. Breezy. Scattered showers and slight chance of thunderstorms in the morning, then scattered showers in the afternoon. Highs 71 to 78. Northeast winds 15 to 25 mph. Chance of rain 50 percent.

Tonight: Breezy. Mostly cloudy with isolated showers in the evening, then partly cloudy with scattered showers after midnight. Lows around 62. Northeast winds 15 to 20 mph. Chance of rain 30 percent.

Monday: Mostly sunny in the morning then becoming mostly cloudy. Breezy. Scattered showers. Highs 71 to 78. Northeast winds 15 to 20 mph. Chance of rain 40 percent.

Kaunakakai

Today: Partly sunny. Breezy. Slight chance of thunderstorms and isolated showers in the morning, then scattered showers in the afternoon. Highs 77 to 85. Northeast winds 15 to 25 mph. Chance of rain 50 percent.

Tonight: Partly cloudy with isolated showers. Lows 63 to 73. Northeast winds around 15 mph. Chance of rain 20 percent.

Monday: Mostly sunny in the morning then becoming partly sunny. Isolated showers. Highs 77 to 85. Northeast winds around 15 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Unstable and wet trade winds will continue into Monday morning for most areas as a combination of low level shower bands combine forces with an upper level trough over the islands. However, the threat for heavy rain and flash flooding over the islands has diminished this morning. Drier trends will spread from north to south across the state through Monday under a building upper level ridge. Increasing shower trends are possible mainly over windward and mountain areas from Tuesday night through Thursday.

Discussion

The satellite loop this morning continues to show an upper level trough over the islands with a subtropical jet stream lingering over the Big Island. Unstable low level clouds and showers will begin to decrease in coverage today as we slowly transition to a more stable environment. Local radar continues to show a few areas of heavy rainfall and thunderstorms this evening, mainly in the coastal and offshore waters south and west of the Big Island. The threat for heavy rain and flash flooding has diminished this morning as the upper trough continues to weaken over the islands. Therefore, the Flash Flood Watch was cancelled this morning. Cold air aloft associated with the upper level trough will keep periods of snow showers in the forecast for the highest summits of the Big Island above 12,000 feet elevation, and a Winter Weather Advisory was issued for up to 2 inches of additional snowfall.
The short range forecast guidance continues to suggest wet trade wind weather will continue into early Monday morning for some areas as the upper trough slowly drifts south. Isolated thunderstorms remain in the forecast over the central and eastern islands.The northwest islands of Kauai and Oahu will begin to see drying trends by this afternoon as more stable conditions move in from the north. These drier trends are caused by a building upper level ridge producing stronger subsidence over the region, leading to a stronger trade wind temperature inversion and more stable clouds across the area. Otherwise the surface ridge will remain locked in place north of the islands allowing continued moderate to breezy trade winds.
Tuesday through Thursday, a high pressure system will drift eastward across the Central Pacific basin passing by just north of the island chain on Wednesday and Thursday. This system will push unsettled clouds associated with a dissipated frontal cloud band into windward and mountain areas of each island. Expect a slight increase in rainfall trends from Tuesday night into Thursday mainly over windward and mountain areas, favoring the overnight to early morning hours.
Friday and Saturday, more typical fair weather trade winds are forecast from Friday into Saturday with a high pressure ridge remaining north of the state. Long range guidance is hinting at a low level trough moving through the easterly trade winds possibly enhancing rainfall over the eastern slopes of the Big Island by Saturday night and then spreading periods of rainfall westward across the rest of the state into next Sunday. As expected the current long range model solutions differ a bit on the strength and instability associated with this low level trough. More island by island precipitation details later as the forecast time period grows closer.

Aviation

High pressure ridge anchored northwest of the state will continue to maintain breezy trade winds that will focus showers along windward slopes of the islands through tonight. An upper trough lingering over the eastern portions of the state will enhance shower coverage and intensity over Maui and the Big Island, along will enhancing the chance for isolated thunderstorms. Tempo mtn obsc potential, due to MVFR cigs and vsby, will continue across portions of the windward zones again today. These conditions are expected to continue along some windward zones through tonight as moist trade wind flow continues.
AIRMET Tango continues for low lvl mechanical leeward turbulence while moderate upper level turb conditions have diminished over the islands. The treat of light icing continues to diminish across the islands, but lingers in a narrowing area over the eastern portions of the state in a layer above 150kft.

Marine

Surface high pressure centered northwest of the islands will maintain a tight enough pressure gradient down across the region to hold ongoing moderate to strong trade winds in place the next several days. Except for the windward Oahu and windward Big island waters, a Small Craft Advisory (SCA) is in effect for the remaining nearshore waters east of Oahu through today. An SCA is in effect for the notoriously windier waters surrounding Maui County and those waters south of Big Island through Monday night.
Very small northwest to north swells are traveling around the islands. These have and will continue to generate small surf along many north and west facing shorelines through Tuesday. A larger medium period northwest swell associated with former Typhoon Malakas is timed to arrive late Tuesday and Wednesday. This approximate five foot, 10 to 14 second period northwest swell will boost north and west facing shore surf up to near head high to slightly above head high along more northern exposures going into mid week. These heights will persist through the end of the week. East shore surf will remain elevated and choppy in the short term before subtly falling off in the coming days as the relatively longer period east swell diminishes in response to weakening upstream trades. Recent seasonal south shore surf from the passage of a slightly larger south swell will retain these weekend heights through Monday.

HFO Watches/Warnings/Advisories

Winter Weather Advisory until 6 PM HST this evening for Big Island Summits above 12000 feet.
Small Craft Advisory until 6 AM HST Tuesday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.
Small Craft Advisory until 6 PM HST this evening for Oahu Leeward Waters, Kaiwi Channel, Maui County Windward Waters, Maui County Leeward Waters.

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Data Courtesy of NOAA.gov