Photo Credit: Tyler Rooke

West Side

Today: Mostly sunny with isolated showers. Haze. Highs 72 to 84. Light winds. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Haze. Lows 64 to 72. Light winds. Chance of rain 20 percent.

Washingtons Birthday: Mostly sunny in the morning then becoming partly sunny. Scattered showers. Haze. Highs 72 to 83. Light winds becoming north up to 10 mph in the afternoon. Chance of rain 40 percent.

South Side

Today: Mostly sunny with isolated showers. Haze. Highs 75 to 85. Light winds. Chance of rain 20 percent.

Tonight: Partly cloudy. Haze. Lows around 67. Light winds.

Washingtons Birthday: Mostly sunny with scattered showers. Haze. Highs 73 to 85. Light winds becoming northwest up to 10 mph in the afternoon. Chance of rain 30 percent.

North Shore

Today: Mostly sunny with isolated showers. Haze. Highs 78 to 83 near the shore to around 69 near 5000 feet. East winds up to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Haze. Lows around 67 near the shore to around 53 near 5000 feet. Southeast winds up to 10 mph.

Washingtons Birthday: Mostly sunny with scattered showers. Haze. Highs around 80 near the shore to around 68 near 5000 feet. East winds up to 10 mph. Chance of rain 30 percent.

Central Maui

Today: Mostly sunny with isolated showers. Haze. Highs 81 to 86. Northeast winds up to 10 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Haze. Lows around 66. Light winds.

Washingtons Birthday: Mostly sunny with scattered showers. Haze. Highs 80 to 85. Light winds becoming northeast around 10 mph in the afternoon. Chance of rain 30 percent.

Upcountry

Today: Mostly sunny with scattered showers. Haze. Highs around 62 at the visitor center to around 60 at the summit. Light winds. Chance of rain 40 percent.

Tonight: Partly cloudy. Haze. Lows around 45 at the visitor center to around 42 at the summit. Light winds.

Washingtons Birthday: Mostly sunny with isolated showers. Haze. Highs 52 to 69. Light winds becoming northeast up to 15 mph in the afternoon. Chance of rain 20 percent.

East Maui

Today: Mostly sunny with isolated showers. Haze. Highs 78 to 83 near the shore to around 69 near 5000 feet. East winds up to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Haze. Lows around 67 near the shore to around 53 near 5000 feet. Southeast winds up to 10 mph.

Washingtons Birthday: Mostly sunny with scattered showers. Haze. Highs around 80 near the shore to around 68 near 5000 feet. East winds up to 10 mph. Chance of rain 30 percent.

Lanai City

Today: Mostly sunny in the morning then becoming partly sunny. Scattered showers. Haze. Highs 69 to 79. Light winds. Chance of rain 40 percent.

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Scattered showers. Haze. Lows 59 to 66. Light winds. Chance of rain 30 percent.

Washingtons Birthday: Mostly sunny in the morning then becoming partly sunny. Scattered showers. Haze. Highs 67 to 77. Light winds. Chance of rain 40 percent.

Kaunakakai

Today: Mostly sunny with isolated showers. Haze. Highs 68 to 84. Light winds. Chance of rain 20 percent.

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Isolated showers. Haze. Lows 54 to 71. Light winds. Chance of rain 20 percent.

Washingtons Birthday: Partly sunny with scattered showers. Haze. Highs 67 to 82. Light winds becoming north up to 10 mph in the afternoon. Chance of rain 50 percent.

Detailed Forecast

Synopsis

A cold front and prefrontal cloud band will produce a 24 to 36 hour period of unsettled wet weather over the western Hawaiian Islands. Thunderstorms and localized flooding are possible threats with this next system for Niihau, Kauai and Oahu, from this evening through the Monday time period. The frontal band will stall out and diminish near Oahu from Monday night through Tuesday as more stable easterly trade winds return to the region with periods of windward and mountain showers lasting through Wednesday night. By Thursday, a strong ridge aloft will build in over the state, producing dry and stable trends lasting through next weekend. Lighter winds are forecast from Friday onward as another shallow cold front approaches the state from the northwest direction.

Discussion

The satellite imagery this morning continues to show a cold front on approach to the Hawaiian Islands, currently located 600 miles northwest of Kauai. A band of low level clouds, in the warm sector ahead of the approaching front, is producing showers over Kauai this morning. Weather conditions near Kauai will grow more unstable today as strengthening southerly surface winds converge, advecting additional unstable moisture up from the south, and enhancing shower activity over the Garden Isle. Radar imagery currently shows numerous showers moving into Kauai from the south, these showers will slowly intensify through the day. Cloud bands with scattered showers are also shown on local radar and satellite imagery moving into the east and southeast slopes of the Big Island this morning.
The short range weather forecast trends towards the wet side for the western half of the state as the prefrontal convergence cloud band near Kauai and the approaching cold front combine forces over the western islands from tonight into Monday. This frontal system will weaken on approach, stalling and dissipating near Oahu by Monday. Expect a 24 to 36 hour period of wet weather through Monday over the western Hawaiian Islands. Shower bands moving up from the south have potential to produce localized flooding in some areas where they can line up and train over island mountains, with possible threats for Kauai and Oahu starting later this evening through Monday. The eastern most extent of thunderstorm coverage is limited to the western half of the state. By Monday afternoon, the main band of moisture should be centered around Oahu along the stalled out front. Enhanced shower activity will rapidly diminish from Monday night to Tuesday.
Molokai will see increasing shower trends into the scattered to numerous range from Monday afternoon through the Monday overnight hours, as the frontal band stalls out near Oahu. Maui and Lanai will likely see less shower activity into the scattered range as the front will stall too far west of these islands for much enhanced rainfall. Big Island showers will favor east and southeast slopes in this pattern through Monday night, then back to typical easterly trade wind weather from Tuesday morning onward.
By Tuesday, easterly trade winds will sweep more stable conditions back into the islands with periods of our typical windward and mountain showers, favoring the overnight to early morning hours. An upper level ridge will move over the state and strengthen from Wednesday night into next weekend, limiting shower activity statewide. Another shallow cold front will approach the islands from the northwest direction from Friday into next weekend, weakening the surface ridge, and producing lighter southeast winds across the region.

Aviation

A band of clouds and showers moving into the western half of the state will continue to bring periods of MVFR or lower conditions to Kauai and Oahu this morning. Meanwhile, drier air will briefly move into the eastern half of the state keeping conditions mainly VFR. A cold front will approach the region from the northwest today. Southerly winds ahead of the front will bring additional bands of moisture to Kauai this afternoon and eventually Oahu tonight resulting in increased chances of MVFR or lower across Kauai and Oahu. Otherwise, conditions should remain mainly VFR.
AIRMET Sierra remains in effect for mountain obscuration across Kauai and Oahu this morning with conditions likely continuing through the day. AIRMET Sierra is also in effect for Molokai and windward and SE portions of the Big Island, but expect conditions to continue to improve through the morning.

Marine

Moderate southeast flow will prevail across the waters today, slowly veering more southerly late today into tonight as a frontal system approaches the region from the northwest. Behind the front expect moderate northerly winds. Enough instability will exist along and ahead of the front to bring a slight chance of thunderstorms over waters surrounding Kauai and Oahu late tonight through Monday. However, the front is expected to dissipate near Oahu Monday night into Tuesday. Moderate easterly or southeasterly background winds will be in place through at least mid-week.
Northwest swell will continue to slowly lower today and maintain surf heights well below High Surf Advisory (HSA) Criteria. Deep low pressure presently situated just south southeast of Russia's Kamchatka Peninsula will deliver a large, long period northwest (310-320) swell early this week with long period forerunners arriving by tonight. The distant source region of this swell compared to previous swell will focus energy in the longer period bands increasing confidence that surf will rise to well within the HSA range Monday and perhaps approach warning criteria for N and W facing shores as it peaks Monday night through Tuesday. A Small Craft Advisory for seas may become necessary for the northern waters during this time. The swell will then gradually subsides through mid- to late week.
Moderate SE flow maintains small chop along E facing shores while background energy out of the southerly quadrant maintains small surf for S facing shores.

HFO Watches/Warnings/Advisories

None.

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Data Courtesy of NOAA.gov