Hilo

Today: Mostly cloudy. Showers in the morning, then scattered showers in the afternoon. Highs around 86 near the shore to 70 to 75 at 4000 feet. North winds up to 15 mph. Chance of rain 90 percent.

Tonight: Cloudy. Showers in the evening, then numerous showers after midnight. Lows around 69 near the shore to around 55 at 4000 feet. Light winds. Chance of rain 90 percent.

Friday: Cloudy. Showers in the morning, then showers and isolated thunderstorms in the afternoon. Highs around 86 near the shore to 70 to 75 at 4000 feet. Northeast winds up to 10 mph. Chance of rain 90 percent.

Kona

Today: Partly sunny. Isolated showers in the morning, then scattered showers and slight chance of thunderstorms in the afternoon. Highs 83 to 88 near the shore to around 70 near 5000 feet. Southeast winds up to 10 mph shifting to the west in the afternoon. Chance of rain 50 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Scattered showers. Lows 70 to 76 near the shore to around 56 near 5000 feet. Light winds. Chance of rain 50 percent.

Friday: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers and isolated thunderstorms in the afternoon. Highs 83 to 88 near the shore to around 70 near 5000 feet. Light winds. Chance of rain 50 percent.

Waimea

Today: Breezy. Partly sunny with scattered showers. Highs around 84 near the shore to 70 to 81 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Showers in the evening, then numerous showers after midnight. Lows around 69 near the shore to 57 to 63 near 3000 feet. East winds around 10 mph. Chance of rain 90 percent.

Friday: Numerous showers in the morning, then showers and isolated thunderstorms in the afternoon. Highs around 84 near the shore to 70 to 81 near 3000 feet. East winds around 10 mph. Chance of rain near 100 percent.

Kohala

Today: Breezy. Partly sunny with scattered showers. Highs around 84 near the shore to 70 to 81 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Showers in the evening, then numerous showers after midnight. Lows around 69 near the shore to 57 to 63 near 3000 feet. East winds around 10 mph. Chance of rain 90 percent.

Friday: Numerous showers in the morning, then showers and isolated thunderstorms in the afternoon. Highs around 84 near the shore to 70 to 81 near 3000 feet. East winds around 10 mph. Chance of rain near 100 percent.

South Big Island

Today: Partly sunny. Scattered showers and slight chance of thunderstorms in the afternoon. Highs around 87 near the shore to around 74 near 5000 feet. Northeast winds up to 15 mph shifting to the east in the afternoon. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows around 71 near the shore to around 54 near 5000 feet. Northeast winds around 10 mph. Chance of rain 40 percent.

Friday: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers and isolated thunderstorms in the afternoon. Highs around 87 near the shore to around 74 near 5000 feet. East winds 10 to 15 mph. Chance of rain 50 percent.

Puna

Today: Mostly cloudy. Showers in the morning, then scattered showers in the afternoon. Highs around 86 near the shore to 70 to 75 at 4000 feet. North winds up to 15 mph. Chance of rain 90 percent.

Tonight: Cloudy. Showers in the evening, then numerous showers after midnight. Lows around 69 near the shore to around 55 at 4000 feet. Light winds. Chance of rain 90 percent.

Friday: Cloudy. Showers in the morning, then showers and isolated thunderstorms in the afternoon. Highs around 86 near the shore to 70 to 75 at 4000 feet. Northeast winds up to 10 mph. Chance of rain 90 percent.

Waikoloa

Today: Partly sunny. Breezy. Isolated showers in the morning, then scattered showers and slight chance of thunderstorms in the afternoon. Highs around 87 near the shore to 71 to 77 above 4000 feet. Southeast winds up to 20 mph shifting to the northeast in the afternoon. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows 71 to 76 near the shore to 52 to 59 above 4000 feet. Light winds. Chance of rain 50 percent.

Friday: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers and isolated thunderstorms in the afternoon. Highs around 87 near the shore to 71 to 77 above 4000 feet. Light winds. Chance of rain 50 percent.

Detailed Forecast

Synopsis

A cold front far north of the islands will move south towards Hawaii today. An upper level disturbance is forming over the region this morning as the front stalls out north of the islands, creating continued unstable weather conditions with periods of enhanced showers for all islands through Saturday night. More stable conditions return for the western half of the state from Sunday into early next week. Windward Maui and the Big Island will continue to see enhanced shower trends through Monday. High pressure building back in north of the region will produce moderate to breezy trade winds from Tuesday onward in a more stable weather pattern.

Discussion

A cold front roughly 800 miles north of Oahu will continue to move south towards the Hawaiian Islands today. Water vapor satellite imagery shows an upper level low forming just north of the islands this morning. This upper low will drift slowly across the state into the weekend. Upper level soundings from 2 AM HST (12Z) at Hilo show this instability in the atmosphere, with trade wind temperature inversion height are hovering around the 13,000 foot level. This means cloud heights will build higher resulting in periods of enhanced shower activity.
The high pressure ridge north of the region will weaken over the next 24 hours as the cold front approaches the region from the north. Trade wind speeds will also decrease in strength for the next few days. Periods of unsettled weather conditions and showers will continue to develop across the state into the upcoming weekend. Periods of moderate to locally heavy showers are expected over all islands through Sunday night. The highest chances for rainfall amounts are forecast over windward and mountain sections of each island. These enhanced showers will also tend to favor the typical overnight to early morning hours. That said, some of the stronger showers that develop will bring brief periods of rainfall to the typically drier leeward areas. Isolated thunderstorms are possible over the Big Island on Friday and Saturday afternoon.
By Sunday the forecast guidance showers this upper low lifting slowly to the northeast as a strong high pressure system builds in north of the state. The combination of these two changes will produce a drying trend for the western half of the state starting on Monday. However, one wrinkle in the forecast remains from Sunday to Monday as a weak low level trough (700mb streamlines) drifts into the eastern islands as it passes just south of the island chain. This weak trough will extend enhanced shower activity over windward and eastern sections of Maui and the Big Island through Monday night.
Trade winds will strengthen back into the moderate to breezy range from next week Tuesday onward as a strong high pressure system builds in north of the region. A high pressure ridge aloft will produce stabilizing trends for all islands with only brief showers lingering over windward and mountain areas, mainly in the overnight to early morning hours.

Aviation

With high pressure persisting far north and northeast of the islands, trade winds will remain moderate to breezy across the area. Showers and accompanying MVFR conditions will mainly affect windward and mauka sections statewide. Also, an upper air disturbance in the region will likely enhance showers overall and marginally back surface winds toward the north and northeast.
AIRMETs are in effect for mountain obscuration over windward areas of the Big Island and Maui, and for low level turbulence downwind of higher elevations statewide.

Marine

Strong high pressure far northeast of the area will continue to produce moderate to locally strong trade winds across the area through this morning. The Small Craft Advisory has been extended for typically windy waters around Maui County and the Big Island through the afternoon today. Trade winds will gradually become a bit lighter throughout the day and remain on the lighter side into the early part of the weekend. Trade winds may begin to pick up on Sunday as the high tracks to our north.
A series of rather small short period northerly swells are expected through Tuesday. A slightly larger and longer period northwest swell may arrive Sunday night and Monday and linger into Tuesday. The current small long period south swell will linger through today with a slightly larger long period south swell expected to fill in later today, peak tomorrow and slowly subside through the weekend. Another similar size south swell may arrive Tuesday and Wednesday next week. Short period choppy surf will remain slightly elevated along east facing shores through today before diminishing a bit over the weekend. Strengthening trade winds early next week will likely boost east facing shores once again.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 PM HST this evening for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

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Data Courtesy of NOAA.gov