West Side

Today: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 76 to 87. Northeast winds up to 15 mph. Chance of rain 40 percent.

Tonight: Mostly clear. Lows 66 to 75. East winds up to 10 mph in the evening becoming light.

Thursday: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 75 to 87. South winds up to 10 mph. Chance of rain 40 percent.

South Side

Today: Mostly sunny. Isolated showers in the morning. Highs 78 to 89. North winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 20 percent.

Tonight: Mostly clear. Lows 68 to 73. North winds up to 15 mph in the evening becoming light.

Thursday: Mostly sunny with isolated showers. Highs 77 to 88. South winds up to 15 mph shifting to the southwest in the afternoon. Chance of rain 20 percent.

North Shore

Today: Partly sunny with scattered showers. Highs 81 to 86 near the shore to around 68 near 5000 feet. Northeast winds up to 15 mph. Chance of rain 50 percent.

Tonight: Partly cloudy. Scattered showers in the evening. Lows around 72 near the shore to around 55 near 5000 feet. Southeast winds up to 10 mph in the evening becoming light. Chance of rain 40 percent.

Thursday: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 81 to 87 near the shore to around 67 near 5000 feet. Light winds. Chance of rain 50 percent.

Central Maui

Today: Mostly sunny. Isolated showers in the morning. Highs 81 to 88. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Tonight: Mostly clear. Lows around 70. Northeast winds up to 15 mph in the evening becoming light.

Thursday: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 83 to 88. Southwest winds up to 15 mph. Chance of rain 40 percent.

Upcountry

Today: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs 55 to 69. Northeast winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly clear. Lows 43 to 54. East winds up to 10 mph in the evening becoming light.

Thursday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs around 61 at the visitor center to around 63 at the summit. South winds up to 10 mph. Chance of rain 50 percent.

East Maui

Today: Partly sunny with scattered showers. Highs 81 to 86 near the shore to around 68 near 5000 feet. Northeast winds up to 15 mph. Chance of rain 50 percent.

Tonight: Partly cloudy. Scattered showers in the evening. Lows around 72 near the shore to around 55 near 5000 feet. Southeast winds up to 10 mph in the evening becoming light. Chance of rain 40 percent.

Thursday: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 81 to 87 near the shore to around 67 near 5000 feet. Light winds. Chance of rain 50 percent.

Lanai City

Today: Mostly sunny. Isolated showers in the afternoon. Highs 71 to 82. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Isolated showers after midnight. Lows 61 to 68. Northeast winds up to 15 mph in the evening becoming light. Chance of rain 20 percent.

Thursday: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 70 to 81. South winds around 10 mph. Chance of rain 40 percent.

Kaunakakai

Today: Mostly sunny with isolated showers. Highs 73 to 90. Northeast winds up to 15 mph. Chance of rain 20 percent.

Tonight: Mostly clear. Lows 57 to 74. Northeast winds up to 15 mph in the evening becoming light.

Thursday: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 72 to 88. Southeast winds up to 10 mph. Chance of rain 40 percent.

Detailed Forecast

Synopsis

A low pressure system north of the Hawaiian Islands will drift south approaching the islands this week. A trailing cold front along the south side of this system will weaken into a surface trough as it stalls out near Kauai from Thursday into Friday. Trade winds will diminish into light and variable winds by tonight with daytime sea breezes and overnight land breezes for all islands through the weekend. The highest chances for showers will develop by Thursday and Friday along the stalled out surface trough near Kauai and Niihau. Additional enhanced rainfall may develop on Friday and Saturday afternoon along the Kona slopes of the Big Island mountains. This low pressure system and surface trough drifts westward away from the state over the weekend allowing trade winds to slowly build back into the islands during the first half of next week.

Discussion

In the big picture satellite imagery this morning we see the subtropical jet stream producing a band of cirrus clouds just south of the Big Island. Fairly stable cumulus clouds just upstream are riding into the islands on the weakening easterly trade winds, producing just a few showers over the windward island mountains this morning. Farther north we see a cut off low pressure system and weakening cold front drifting ever so slowly towards the islands. The cold front will weaken into a surface trough by Thursday and Friday as the southward motion of the trough stalls out near Kauai and Niihau.
For today, a weak mid level ridge over the state will keep stable subsidence over the region through tonight. Subsidence temperature inversion heights will range from 5,000 to 7,000 feet elevation today and tonight limiting cloud growth and shower activity. These stable conditions will begin to change for the western islands of Niihau, Kauai and to a lesser extent over Oahu on Thursday, as a surface trough drifts in from the north. Expect clouds and enhanced shower activity along this surface trough with the potential for brief slow moving heavy rain at times and isolated thunderstorms near the Garden Isle of Kauai from Thursday into Friday. Oahu may see some shower enhancement to a lesser degree as the island will remain farther away from the stalled surface boundary.
Another noticeable change in the weather will occur near the Big Island as the low pressure system north of the state drifts closer it will weaken the ridge over the region and induce a trough to develop just south of the Hawaiian Islands. This induced low level trough will pull up and inject deeper unstable tropical moisture into the sea breeze weather pattern over the Big Island from Friday into Saturday. This deeper unstable moisture will combine forces with elevated daytime surface heating along the slopes of Mauna Kea and Mauna Loa, potentially triggering a brief period of enhanced shower activity each afternoon on Friday and Saturday. There may be enough instability for brief thunderstorm development and heavier shower activity along the Kona slopes of the Big Island. Stay tuned.
The low pressure system north of the island chain will begin to drift westward away from the Hawaiian Islands from Sunday into Monday. This change in the weather pattern will allow the broad ridge north of the region to build in allowing more stable trade wind weather to return to the islands by next week Tuesday and Wednesday. Expect moderate to locally breezy trade winds along with brief passing showers during this time period, favoring the windward mountain areas in the overnight to early morning hours.

Aviation

A low pressure system and weakening cold front will approach the islands. Trade winds will diminish into light and variable land and sea breezes from tonight lasting into the weekend. Clouds and showers may increase along a stalled surface trough near the island of Kauai by Thursday and Friday. Showers may be heavy at times with periods of MVFR conditions. Isolated thunderstorms are possible.
No AIRMETs are currently in effect.

Marine

No changes to the forecast with the morning package. Locally fresh trades are expected to weaken today, and become light out of the south, or variable through the weekend. This is in response to a low pressure system developing northeast of the islands. An upper level trough associated with the surface feature will bring the chance for thunderstorms near Kauai Thursday and Friday. This upper level feature will provide the chance for thunderstorms over various parts of the offshore waters over the next several days.
Low amplitude energy out of the south will maintain surf near seasonal average along south facing shores through the week. A small, long period southerly swell then arrives this weekend bringing a small bump to exposed shorelines.
Strong northwesterlies around low pressure evolving to the NE of the islands will direct a moderate N-NNE fresh swell toward area waters late tonight, that will peak Thursday, and then subside during the remainder of the week. This is followed by a small, medium period NW swell that will maintain elevated surf along N and W facing shores as it peaks Saturday night into Sunday.

Fire weather

Decreasing wind speeds into the light and variable range and increasing humidity trends will combine forces to keep fire weather conditions below critical thresholds for the next seven days. Temperature inversion heights near Maui and the Big Island today will range from 6,000 to 7,000 feet elevation.

HFO Watches/Warnings/Advisories

None.

Data Courtesy of NOAA.gov