Today: Mostly cloudy. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 80 near the shore to 65 to 70 at 4000 feet. Southeast winds up to 15 mph. Chance of rain 50 percent.
Tonight: Mostly cloudy with scattered showers. Lows 64 to 71 near the shore to around 53 at 4000 feet. Southwest winds up to 10 mph. Chance of rain 50 percent.
Monday: Breezy. Mostly cloudy with numerous showers. Highs around 81 near the shore to 66 to 71 at 4000 feet. South winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 70 percent.
Kona
Today: Mostly sunny. Scattered showers in the afternoon. Highs 78 to 83 near the shore to around 65 near 5000 feet. Northwest winds up to 10 mph. Chance of rain 30 percent.
Tonight: Partly cloudy with isolated showers. Lows around 68 near the shore to around 53 near 5000 feet. Light winds becoming southeast up to 10 mph after midnight. Chance of rain 20 percent.
ARTICLE CONTINUES BELOW AD
ARTICLE CONTINUES BELOW AD
Monday: Breezy. Partly sunny with scattered showers. Highs 79 to 84 near the shore to around 66 near 5000 feet. Southeast winds up to 20 mph shifting to the south 10 to 20 mph in the afternoon. Chance of rain 50 percent.
Waimea
Today: Mostly sunny in the morning then becoming partly sunny. Isolated showers. Highs around 78 near the shore to 65 to 75 near 3000 feet. Northwest winds up to 10 mph shifting to the northeast in the afternoon. Chance of rain 20 percent.
Tonight: Partly cloudy. Lows around 67 near the shore to 53 to 61 near 3000 feet. Light winds.
Monday: Partly sunny with scattered showers. Highs around 79 near the shore to 66 to 76 near 3000 feet. Southeast winds up to 10 mph shifting to the northwest in the afternoon. Chance of rain 30 percent.
Kohala
Today: Mostly sunny in the morning then becoming partly sunny. Isolated showers. Highs around 78 near the shore to 65 to 75 near 3000 feet. Northwest winds up to 10 mph shifting to the northeast in the afternoon. Chance of rain 20 percent.
ARTICLE CONTINUES BELOW AD
Tonight: Partly cloudy. Lows around 67 near the shore to 53 to 61 near 3000 feet. Light winds.
Monday: Partly sunny with scattered showers. Highs around 79 near the shore to 66 to 76 near 3000 feet. Southeast winds up to 10 mph shifting to the northwest in the afternoon. Chance of rain 30 percent.
South Big Island
Today: Breezy. Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs around 82 near the shore to around 69 near 5000 feet. East winds up to 20 mph. Chance of rain 30 percent.
Tonight: Mostly cloudy with scattered showers. Lows around 69 near the shore to around 53 near 5000 feet. East winds up to 15 mph. Chance of rain 50 percent.
Monday: Mostly cloudy with numerous showers. Highs around 83 near the shore to around 70 near 5000 feet. East winds up to 15 mph shifting to the southeast in the afternoon. Chance of rain 70 percent.
Puna
ARTICLE CONTINUES BELOW AD
Today: Mostly cloudy. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 80 near the shore to 65 to 70 at 4000 feet. Southeast winds up to 15 mph. Chance of rain 50 percent.
Tonight: Mostly cloudy with scattered showers. Lows 64 to 71 near the shore to around 53 at 4000 feet. Southwest winds up to 10 mph. Chance of rain 50 percent.
Monday: Breezy. Mostly cloudy with numerous showers. Highs around 81 near the shore to 66 to 71 at 4000 feet. South winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 70 percent.
Waikoloa
Today: Mostly sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs around 82 near the shore to 66 to 72 above 4000 feet. Northwest winds up to 10 mph. Chance of rain 20 percent.
Tonight: Partly cloudy with isolated showers. Lows 66 to 72 near the shore to 48 to 58 above 4000 feet. Light winds becoming southeast up to 15 mph after midnight. Chance of rain 20 percent.
Monday: Partly sunny with scattered showers. Highs around 83 near the shore to 67 to 73 above 4000 feet. Southwest winds up to 15 mph shifting to the west in the afternoon. Chance of rain 40 percent.
Detailed Forecast
Synopsis
Deep tropical moisture being drawn northward ahead of an approaching cold front and an upper disturbance will lead to an increasing threat of heavy rainfall tonight through the first half of the week. Strengthening southerly winds, periods of heavy rainfall, and thunderstorms will accompany this front as it moves through from west to east. The active pattern will continue through the second half of the week as another system approaches and moves into the area.
Discussion
Guidance remains in good agreement and shows a strong pulse aloft approaching the region today, then closing off into an upper low a few hundred miles north-northwest of the islands tonight through Monday night. Strong surface cyclogenesis with a gale low forming along the attendant cold front is shown as the system advances toward the islands today. The low-level flow will gradually respond locally and begin to strengthen as it veers out of the south.
Deep tropical moisture being drawn northward ahead of the approaching system combined with lowering upper heights and increasing instability will lead to a period of widespread rainfall with embedded thunderstorms later today through the first half of the week. In addition to the increasing threat of flash flooding where the heavy rainfall becomes focused during this period, embedded thunderstorms and gusty south-southwest winds (damaging downsloping winds possible Monday through Tuesday) are anticipated. For timing, these threats will be most likely over the western end of the state this evening into Monday, then over the rest of the state Monday through Tuesday.
The front will gradually dissipate near Maui County Tuesday night into Wednesday. Winds will continue to veer out of the west- southwest, but ease slightly during this time. Lingering shower activity will continue into Wednesday, but rainfall intensity should trend down during the day as the front dissipates and the upper support lifts northward and opens up.
Models remain consistent in that the front during the first half of the week will be quickly followed by another system beginning on Thursday. Although it remains too early to discern many details regarding this second system, indications are that another round of heavy showers, thunderstorms and stronger winds will return to the islands from Thursday onward.
Aviation
A nearby surface ridge is supporting light to moderate SE-S winds, with limited cloud/shower coverage seen near Kauai and Oahu. Increased clouds and showers are noted over windward portions of the Big Island and E Maui, where persistent MVFR VIS/CIG in SHRA have led to the issuance of AIRMET SIERRA for mountain obscuration.
Some decrease in shower coverage is anticipated over windward Maui/Big Island later today, as the low-level flow becomes increasingly southerly and gradually strengthens. Daytime heating will lead to increased clouds over interior areas statewide this afternoon with ISOL MVFR CIG, while an approaching front will bring increasing rain chances later in the day to Kauai. The front will likely bring increased rain chances to Oahu by tonight, and potentially Maui County by early Tuesday. The front will bring widespread MVFR VIS/CIG in SHRA and ISOL IFR VIS/CIG in +SHRA, with leeward areas likely seeing the greatest coverage.
Marine
The southwest edge of the high pressure ridge is moving over the Hawaiian Islands today as a low pressure system and cold front approaches the region from the northwest. The Small Craft Advisory near some of the Big Island waters was cancelled today as wind speeds diminish. Unstable showers will likely develop ahead of the frontal band potentially affecting waters surrounding Kauai later this afternoon and Oahu waters by tonight.
A surface low will deepen along the frontal boundary just northwest to north of Kauai today, causing winds to veer from a southerly to southwesterly direction over the western islands. These southerly winds spreading statewide by Monday along with increasing shower activity and possible thunderstorms as the cold front marches down the island chain. The front is expected to weaken and stall near Maui on Wednesday, with winds easing and shifting westerly. Uncertainty increases Thursday and Friday, but a surface low may develop near the islands, raising chances for gusty winds and thunderstorms.
The current north-northwest (330 degree) swell will continue to slowly decline today. The next moderate northwest (310-320 degree) swell is due to arrive Monday, and may push north shore surf to the advisory levels from Tuesday into Wednesday. Forecast confidence decreases later in the week due to uncertainty in the location and intensity of a surface low developing near Hawaii.
East shore surf will decline today with small surf through the first half of the week as the local winds veer from a more southerly to southwesterly direction. Small surf will also continue on south shores this week, and conditions may become rough as southerly to southwesterly winds increase on Monday and Tuesday.
HFO Watches/Warnings/Advisories
Flood Watch from this evening through Tuesday afternoon for Niihau, Kauai Leeward, Kauai Mountains, Waianae Coast, Oahu North Shore, Olomana, Central Oahu, Waianae Mountains, Lanai Mauka, Kahoolawe, Maui Windward West, Maui Leeward West, Haleakala Summit, Kona, Kohala, Big Island Interior, Kauai North, Kauai East, Kauai South, East Honolulu, Honolulu Metro, Ewa Plain, Koolau Windward, Koolau Leeward, Molokai, Lanai Windward, Lanai Leeward, Lanai South, Maui Central Valley North, Maui Central Valley South, Windward Haleakala, Kipahulu, South Maui/Upcountry, South Haleakala, Big Island South, Big Island Southeast, Big Island East, Big Island North.
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