Photo Credit: Randy Alona Gallegos

West Side

Today: Mostly sunny with isolated showers. Highs 82 to 87. South winds 10 to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Isolated showers early in the evening, then scattered showers in the late evening and overnight. Lows 66 to 73. South winds up to 15 mph. Chance of rain 30 percent.

Tuesday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 82 to 87. Southwest winds up to 10 mph. Chance of rain 30 percent.

South Side

Today: Breezy. Mostly sunny with isolated showers. Highs around 87. Southwest winds 10 to 20 mph. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows around 67. Southwest winds around 10 mph. Chance of rain 20 percent.

Tuesday: Mostly sunny with isolated showers. Highs around 87. Southwest winds 10 to 15 mph decreasing to up to 15 mph in the afternoon. Chance of rain 20 percent.

North Shore

Today: Mostly sunny. Isolated showers in the morning. Highs 79 to 84 near the shore to around 67 near 5000 feet. Southwest winds up to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Isolated showers in the late evening and overnight. Lows 65 to 71 near the shore to around 53 near 5000 feet. South winds up to 15 mph. Chance of rain 20 percent.

Tuesday: Mostly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs 79 to 84 near the shore to around 67 near 5000 feet. Southwest winds up to 10 mph in the morning becoming light. Chance of rain 50 percent.

Central Maui

Today: Mostly sunny. Breezy. Highs around 86. Southwest winds 10 to 20 mph.

Tonight: Partly cloudy. Isolated showers in the late evening and overnight. Lows 65 to 70. South winds 10 to 15 mph. Chance of rain 20 percent.

Tuesday: Mostly sunny with isolated showers. Highs around 86. South winds up to 15 mph shifting to the northeast in the afternoon. Chance of rain 20 percent.

Upcountry

Today: Breezy. Sunny with isolated showers. Highs around 62 at the visitor center to around 59 at the summit. Southwest winds up to 25 mph with gusts to 50 mph. Chance of rain 20 percent.

Tonight: Breezy. Mostly clear with isolated showers. Lows around 48 at the visitor center to around 45 at the summit. Southwest winds up to 25 mph. Chance of rain 20 percent.

Tuesday: Mostly sunny with isolated showers. Highs around 61 at the visitor center to around 58 at the summit. West winds up to 15 mph. Chance of rain 20 percent.

East Maui

Today: Mostly sunny. Isolated showers in the morning. Highs 79 to 84 near the shore to around 67 near 5000 feet. Southwest winds up to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Isolated showers in the late evening and overnight. Lows 65 to 71 near the shore to around 53 near 5000 feet. South winds up to 15 mph. Chance of rain 20 percent.

Tuesday: Mostly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs 79 to 84 near the shore to around 67 near 5000 feet. Southwest winds up to 10 mph in the morning becoming light. Chance of rain 50 percent.

Lanai City

Today: Mostly sunny with isolated showers. Highs 72 to 81. South winds 10 to 15 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy with scattered showers. Lows around 66. South winds around 10 mph. Chance of rain 30 percent.

Tuesday: Partly sunny with scattered showers. Highs 73 to 82. Southwest winds up to 10 mph in the morning becoming light. Chance of rain 50 percent.

Kaunakakai

Today: Mostly sunny with isolated showers. Highs 76 to 87. South winds up to 15 mph shifting to the southwest in the afternoon. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows 60 to 71. South winds 10 to 15 mph. Chance of rain 20 percent.

Tuesday: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 76 to 87. Southwest winds 10 to 15 mph decreasing to up to 10 mph in the afternoon. Chance of rain 50 percent.

Detailed Forecast

Synopsis

A cold front approaching Kauai from the northwest will continue to produce light to moderate south to southwesterly winds across the state through Monday. A prefrontal cloud and shower bands are forecast near Kauai and Oahu through Monday. The forward motion of the cold front will likely stall near Kauai and Oahu from Monday night into Tuesday and then weaken to a trough. Lighter trade winds and afternoon sea breezes will return from Wednesday and Thursday with a weak high pressure ridge building in just north of the state. Another cold front approaches the islands from the northwest on Friday with enhanced showers possible into next Saturday for the northwestern islands.

Discussion

The satellite weather picture this evening shows a weakening cold front approaching Kauai from the northwest. This frontal boundary is roughly 200 miles northwest of Barking Sands. Prefrontal convergence shower bands are developing in the southwesterly flow ahead of the front with moderate to heavy showers moving into Niihau and western Kauai. A few thunderstorms are also forming within these prefrontal bands and chances for thunderstorms remain in the forecast for the Garden Isle through the early morning hours. These southerly winds will interact with the land and sea breeze wind pattern over each island. Small scale wind convergence cloud bands will drive most of the enhanced rainfall in this weather pattern. Flood advisories are possible for Kauai at some point lasting into Tuesday.
A large low pressure system anchored just south of the Aleutian Islands will bring a weakening cold front into the northwestern Hawaiian Islands into Tuesday. This system will continue to break down the ridge north of the islands lasting into next weekend. Lighter large scale winds means that local island scale land and sea breezes will dominate weather conditions through the week. Southerly winds converging with land and sea breezes will enhance some showers over island interior sections and over western and southern slopes. The highest chances for rainfall in this pattern will be over Niihau, Kauai, Oahu and the Ka'u and Puna slopes of the Big Island. That said, pop up showers are possible over all islands at least through Tuesday.
Slightly more stable conditions are forecast across the state from Wednesday through Thursday as an upper level ridge sets up over the island chain. Models are suggesting afternoon to early evening sea breeze showers during this time period. Slight chances remain for a few thunderstorms over the higher slopes on the Big Island each afternoon.
The next cold front may reach Kauai and Niihau by Friday night and then possibly drift into Oahu by Saturday morning. Expect a brief period of enhanced rainfall along the frontal cloud band as it passes through these northwest islands. Moderate north to northeasterly winds behind the front will produce more stable and cooler conditions as the front passes each island.

Aviation

South to southwest winds continue through Monday as the cold front approaches the state. Weak instability aloft and enhanced low level moisture will lead to enhanced shower activity over Kauai, with isolated thunderstorms possible. Otherwise, isolated showers will be possible mainly along south facing slopes and coasts overnight. A surge of deeper moisture will likely bring an increase in showers and the potential for a thunderstorm or two over the Big Island Monday afternoon. Expect periods of MVFR or lower conditions across Kauai tonight and Monday, with predominantly VFR conditions prevailing elsewhere.
AIRMET Sierra is in effect for mountain obscurations across Kauai and will likely continue through the night.

Marine

Expect light southerly winds ahead of an approaching cold front tonight and Monday. The front will stall near Kauai Monday and a slight chance of thunderstorms remains in the forecast along the boundary. The front weakens in place Tuesday and with variable winds through the rest of the work week as another front approaches from the northwest.
A new northwest (320 degree) swell will build in late tonight into Tuesday, then slowly lower through the rest of the week. Surf heights along both west and north facing shores are forecast to peak around the High Surf Advisory threshold on Monday night and Tuesday.
Background surf expected along south facing shores until Monday morning when a long period south swell moves in. Another longer and slightly larger southwest swell will move in Tuesday, peak Wednesday and slowly subside through the rest of the week. Surf heights along east facing shores will remain small through much of next week due to light winds across the Hawaii Region.

HFO Watches/Warnings/Advisories

None.

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Data Courtesy of NOAA.gov