Photo Credit: Tyler Rooke

West Side

Today: Occasional showers and possibly a thunderstorm. Some of the storms could produce heavy rainfall. High near 81. South southwest wind around 5 mph becoming calm in the afternoon. Chance of precipitation is 100%. New rainfall amounts between 2 and 3 inches possible.

Tonight: Occasional showers and possibly a thunderstorm. Some of the storms could produce heavy rainfall. Low around 67. East wind 6 to 9 mph. Chance of precipitation is 100%. New rainfall amounts between 1 and 2 inches possible.

Sunday: Showers likely and possibly a thunderstorm before 1pm, then scattered showers. Some of the storms could produce heavy rainfall. Mostly cloudy, with a high near 81. Northeast wind 7 to 9 mph. Chance of precipitation is 60%. New rainfall amounts of less than a tenth of an inch, except higher amounts possible in thunderstorms.

South Side

Today: Occasional showers and possibly a thunderstorm. Some of the storms could produce heavy rainfall. High near 80. South wind around 6 mph becoming calm in the afternoon. Chance of precipitation is 100%. New rainfall amounts between 3 and 4 inches possible.

Tonight: Occasional showers and possibly a thunderstorm. Some of the storms could produce heavy rainfall. Low around 65. Calm wind becoming north northeast 5 to 7 mph after midnight. Chance of precipitation is 100%. New rainfall amounts between 1 and 2 inches possible.

Sunday: Showers likely and possibly a thunderstorm before noon, then scattered showers. Some of the storms could produce heavy rainfall. Mostly cloudy, with a high near 78. North wind 5 to 8 mph becoming calm in the afternoon. Chance of precipitation is 60%. New precipitation amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.

North Shore

Today: Occasional showers and possibly a thunderstorm. Some of the storms could produce heavy rainfall. High near 78. South southwest wind 5 to 7 mph becoming northeast in the afternoon. Chance of precipitation is 100%. New rainfall amounts between 1 and 2 inches possible.

Tonight: Occasional showers and possibly a thunderstorm. Some of the storms could produce heavy rainfall. Low around 66. East northeast wind 9 to 11 mph. Chance of precipitation is 100%. New rainfall amounts between 1 and 2 inches possible.

Sunday: Showers likely and possibly a thunderstorm before 1pm, then scattered showers. Some of the storms could produce heavy rainfall. Mostly cloudy, with a high near 78. Breezy, with a northeast wind 13 to 15 mph, with gusts as high as 21 mph. Chance of precipitation is 60%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.

Central Maui

Today: Occasional showers and possibly a thunderstorm. Some of the storms could produce heavy rainfall. High near 78. South southwest wind around 5 mph becoming calm. Chance of precipitation is 100%. New rainfall amounts between 2 and 3 inches possible.

Tonight: Occasional showers and possibly a thunderstorm. Some of the storms could produce heavy rainfall. Low around 64. Northeast wind 7 to 10 mph. Chance of precipitation is 100%. New rainfall amounts between 1 and 2 inches possible.

Sunday: Showers likely and possibly a thunderstorm before 1pm, then scattered showers. Some of the storms could produce heavy rainfall. Mostly cloudy, with a high near 78. Northeast wind 11 to 14 mph, with gusts as high as 18 mph. Chance of precipitation is 60%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.

Upcountry

Today: Occasional showers and possibly a thunderstorm. Some of the storms could produce heavy rainfall. High near 65. South southwest wind 5 to 8 mph becoming calm. Chance of precipitation is 100%. New rainfall amounts in excess of 4 inches possible.

Tonight: Occasional showers and possibly a thunderstorm. Some of the storms could produce heavy rainfall. Low around 53. North northwest wind around 5 mph becoming calm in the evening. Chance of precipitation is 100%. New rainfall amounts between 1 and 2 inches possible.

Sunday: Showers likely and possibly a thunderstorm before noon, then scattered showers. Some of the storms could produce heavy rainfall. Mostly cloudy, with a high near 64. Light and variable wind becoming north 5 to 9 mph in the morning. Chance of precipitation is 60%. New precipitation amounts between a half and three quarters of an inch possible.

East Maui

Today: Occasional showers and possibly a thunderstorm. Some of the storms could produce heavy rainfall. High near 77. Southwest wind around 6 mph becoming calm in the morning. Chance of precipitation is 100%. New rainfall amounts in excess of 4 inches possible.

Tonight: Occasional showers and possibly a thunderstorm. Some of the storms could produce heavy rainfall. Low around 62. North northeast wind 3 to 6 mph. Chance of precipitation is 100%. New rainfall amounts between 1 and 2 inches possible.

Sunday: Occasional showers and possibly a thunderstorm before 1pm, then scattered showers. Some of the storms could produce heavy rainfall. High near 77. Northeast wind 8 to 13 mph. Chance of precipitation is 90%. New rainfall amounts between a quarter and half of an inch possible.

Lanai City

Today: Occasional showers and possibly a thunderstorm. Some of the storms could produce heavy rainfall. High near 72. Southwest wind 5 to 9 mph becoming calm in the afternoon. Chance of precipitation is 100%. New rainfall amounts between 2 and 3 inches possible.

Tonight: Occasional showers and possibly a thunderstorm before 9pm, then scattered showers. Some of the storms could produce heavy rainfall. Low around 62. Breezy, with a northeast wind 9 to 16 mph, with gusts as high as 22 mph. Chance of precipitation is 90%. New precipitation amounts between 1 and 2 inches possible.

Sunday: Scattered showers. Partly sunny, with a high near 71. Breezy, with a northeast wind 15 to 18 mph, with gusts as high as 25 mph. Chance of precipitation is 30%. New precipitation amounts between a quarter and half of an inch possible.

Kaunakakai

Today: Occasional showers and possibly a thunderstorm. Some of the storms could produce heavy rainfall. High near 79. Calm wind becoming east northeast 5 to 9 mph in the afternoon. Chance of precipitation is 90%. New rainfall amounts between 1 and 2 inches possible.

Tonight: Showers likely and possibly a thunderstorm before 8pm, then scattered showers. Some of the storms could produce heavy rainfall. Mostly cloudy, with a low around 67. Breezy, with an east northeast wind 9 to 15 mph, with gusts as high as 20 mph. Chance of precipitation is 70%. New precipitation amounts between a quarter and half of an inch possible.

Sunday: Scattered showers. Partly sunny, with a high near 79. Breezy, with a northeast wind 11 to 16 mph becoming light and variable in the afternoon. Winds could gust as high as 22 mph. Chance of precipitation is 40%. New precipitation amounts of less than a tenth of an inch possible.

Detailed Forecast

Synopsis

The wet pattern will continue as a cold front moving through stalls over the eastern end of the state this weekend. Heavy showers and a few storms along and ahead of the front combined with saturated grounds will keep the threat for flash flooding in place. Gusty north to northeast winds following the front will focus clouds and showers over windward and mountain locations for Kauai and Oahu. The wet pattern will remain possible through the first half of the upcoming week as low pressure tracks westward across the state.

Discussion

Heavy showers and a few thunderstorms will continue to belt the eastern end of the state as a cold front advances down the island chain this morning and stalls by tonight. This additional rainfall will only aggravate the ongoing flooding issues due to the inundated soils and swollen streams from the week’s heavy rainfall. Although the rainfall will be more widespread over the eastern end of the state, strong north to northeast winds following the front has shifted the rainfall coverage to windward and northern slopes for Kauai and Oahu this morning (rainfall rates ranging from a quarter to half of an inch per hour). In addition to the rainfall, the gusty northerly winds combined with the saturated soils could translate to downed trees today, which could further delay or impact restoration efforts. As a result, the Flash Flood Watch remains in effect statewide and a Wind Advisory is now in effect for Kauai and Niihau today.
For the Big Island Summits, gusty winds along with a wintry mix can be anticipated as a potent shortwave trough dives southeastward into the area. The Winter Weather Advisory for the summits may need to be extended through tonight.
Despite the model inconsistencies this week that have lowered forecast confidence for later this weekend and next week, the last few model cycles between the various solutions have been more consistent and in decent agreement. They depict low pressure positioned northeast of the state along the front beginning to track back toward the islands Sunday, then through the islands as a trough early next week. If this solution evolves as projected, expect gusty northerly winds to hold over the western end of the state and potentially remaining light over the eastern end. This surface feature combined with broad upper troughing over the region will keep the rainfall chances in the forecast. They indicate the low opening and dampening out as it slips west- southwest of the area with trades returning statewide Wednesday through the second half of the week.

Aviation

A frontal system, currently located over Oahu, is forecast to push southeast across the state today. Ahead of this feature, abundant moisture and lift will generate numerous showers and isolated thunderstorms over Molokai, Maui, Lanai, and the Big Island. The heavier showers and storms will likely produce periods of MVFR and IFR ceilings and visibility.
Expect breezy northeast winds behind the front. Thus, most shower activity on Kauai and Oahu will be concentrated along the windward coasts and slopes.
AIRMET SIERRA remains in effect for Kauai, Oahu, Molokai, Lanai, and Maui above 2000 feet due to tempo mountain obscuration from clouds and showers.
AIRMET ZULU remains in effect over Oahu, Molokai, Maui and adjacent waters between 13000 and 24000 feet for tempo light icing.

Marine

A cold front will stall out in this vicinity of the central islands through the remainder of the weekend. An area of low pressure will develop along the stalled out front a couple hundred miles northeast of the islands on Sunday, then slowly open up into a trough as it moves southwestward and through the central islands Monday night and Tuesday. High pressure will then build to the north of the islands Wednesday through late next week. The winds will remain strongest across the western end of the state where the gradient will be tightest through Tuesday, with a more uniform trade wind pattern becoming re-established around the middle of next week. A Small Craft Advisory (SCA) is now in effect for the windward Maui waters and Kaiwi Channel westward through Sunday. This SCA will likely need to be expanded to include most coastal waters tonight as a large north swell moves into the area. SCA conditions will then likely hold in place across much of the marine area through early next week.
A new large north to north-northeast swell will rapidly fill in from northwest to southeast down the island chain today and tonight, hold through the remainder of the weekend, then slowly lower early next week. A High Surf Advisory is now in effect for north facing shores of the smaller islands through Sunday, and has been expanded to include east facing shores of Kauai, Oahu, Molokai, and west facing shores of Maui. This HSA will likely need to be expanded to include east facing shores of Maui, and north and east facing shores of the Big Island tonight. Surf should fall below advisory levels along north facing shores Sunday night, but could hold above the advisory threshold for east facing shores through Tuesday. Additionally due to the northerly swell direction, surges may occur at the entrances to the Kahului and Hilo harbors over the weekend.
A moderate northwest swell will move through the islands Wednesday through late next week. An east swell will gradually lower through the weekend as trade winds upstream of the islands diminish. A more typical short-period trade wind swell will return during the middle to latter part of next week as trade winds over and upstream of the islands increase. Surf along south facing shores will receive a small boost today as a small southwest swell moves through the islands. South shore surf will then fall back to background levels Sunday through late next week.

HFO Watches/Warnings/Advisories

Flash Flood Watch through this afternoon for all Hawaii islands.
Wind Advisory through this afternoon for Niihau, Kauai.
High Surf Advisory through 6 PM HST Sunday for Niihau, Kauai Windward, Kauai Leeward, Oahu North Shore, Oahu Koolau, Olomana, Molokai, Maui Windward West, Maui Leeward West, Maui Central Valley, Windward Haleakala.
Winter Weather Advisory until 6 PM HST this evening for Big Island Summits.
Small Craft Advisory until 6 PM HST Sunday for Kauai Northwest Waters, Kauai Windward Waters, Kauai Leeward Waters, Kauai Channel, Oahu Windward Waters, Oahu Leeward Waters, Kaiwi Channel, Maui County Windward Waters.

Data Courtesy of NOAA.gov