Photo Credit: James Grenz

Hilo

Today: Mostly cloudy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 77 to 82 near the shore to around 65 at 4000 feet. East winds up to 10 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy with scattered showers. Lows 63 to 68 near the shore to around 54 at 4000 feet. East winds up to 10 mph. Chance of rain 50 percent.

Memorial Day: Mostly cloudy with scattered showers. Highs 77 to 82 near the shore to around 66 at 4000 feet. East winds up to 10 mph. Chance of rain 50 percent.

Kona

Today: Partly sunny. Scattered showers in the afternoon. Highs around 84 near the shore to around 65 near 5000 feet. Southwest winds up to 10 mph shifting to the northwest in the afternoon. Chance of rain 50 percent.

Tonight: Mostly cloudy. Scattered showers in the evening. Lows around 72 near the shore to around 51 near 5000 feet. Light winds. Chance of rain 40 percent.

Memorial Day: Mostly cloudy. Isolated showers in the morning, then scattered showers in the afternoon. Highs around 84 near the shore to around 66 near 5000 feet. Northwest winds up to 10 mph. Chance of rain 50 percent.

Waimea

Today: Partly sunny with isolated showers. Highs around 78 near the shore to 66 to 76 near 3000 feet. East winds 10 to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows 62 to 69 near the shore to 54 to 61 near 3000 feet. East winds 10 to 15 mph. Chance of rain 20 percent.

Memorial Day: Mostly sunny in the morning then becoming mostly cloudy. Isolated showers. Highs around 77 near the shore to 66 to 75 near 3000 feet. East winds 10 to 15 mph. Chance of rain 20 percent.

Kohala

Today: Partly sunny with isolated showers. Highs around 78 near the shore to 66 to 76 near 3000 feet. East winds 10 to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy with isolated showers. Lows 62 to 69 near the shore to 54 to 61 near 3000 feet. East winds 10 to 15 mph. Chance of rain 20 percent.

Memorial Day: Mostly sunny in the morning then becoming mostly cloudy. Isolated showers. Highs around 77 near the shore to 66 to 75 near 3000 feet. East winds 10 to 15 mph. Chance of rain 20 percent.

South Big Island

Today: Partly sunny. Breezy. Isolated showers in the afternoon. Highs around 83 near the shore to around 65 near 5000 feet. East winds 10 to 20 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Breezy. Isolated showers in the evening. Lows around 72 near the shore to around 52 near 5000 feet. East winds 10 to 20 mph. Chance of rain 20 percent.

Memorial Day: Partly sunny. Breezy. Isolated showers in the morning, then scattered showers in the afternoon. Highs around 84 near the shore to around 66 near 5000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Puna

Today: Mostly cloudy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 77 to 82 near the shore to around 65 at 4000 feet. East winds up to 10 mph. Chance of rain 70 percent.

Tonight: Mostly cloudy with scattered showers. Lows 63 to 68 near the shore to around 54 at 4000 feet. East winds up to 10 mph. Chance of rain 50 percent.

Memorial Day: Mostly cloudy with scattered showers. Highs 77 to 82 near the shore to around 66 at 4000 feet. East winds up to 10 mph. Chance of rain 50 percent.

Waikoloa

Today: Partly sunny. Isolated showers in the afternoon. Highs around 83 near the shore to 62 to 70 above 4000 feet. Northeast winds around 10 mph shifting to the northwest in the afternoon. Gusts up to 30 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Isolated showers in the evening. Lows around 72 near the shore to around 53 above 4000 feet. North winds around 10 mph shifting to the east after midnight. Chance of rain 20 percent.

Memorial Day: Partly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs 80 to 85 near the shore to 63 to 69 above 4000 feet. Northeast winds around 10 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Broad high pressure north and northeast of the state will maintain moderate to locally breezy easterly trade winds through the week. Showers will mainly favor windward slopes, with areas of high clouds passing overhead at times.

Discussion

Moderate to locally breezy easterly trade winds remain in place, with little change expected through the holiday weekend. The trades are being driven by broad surface high pressure sitting nearly 1600 miles north of the state. A surface trough parked about 600 miles west of Kauai is causing the winds to be more easterly than usual, especially over the western end of the island chain. Mid- level ridging over the islands is maintaining somewhat stable conditions with shallow moisture moving along the trade wind flow. This will continue to focus modest rainfall of around a quarter of an inch or less per day across most windward slopes.
An upper-level trough generally collocated with the surface trough continues to produce heavy showers and thunderstorms about 200 miles west of Kauai. Westerly winds aloft are sending high clouds from this area over Kauai and Oahu, while a separate shield of thin high clouds is streaming over the Big Island. Thunderstorm activity is expected to remain west of the state through the holiday weekend. However, the inversion could be weakened at times near Kauai, with the chance for brief periods of enhanced showers. Radar imagery this morning confirms this, showing an area of scattered light to moderate showers over portions of Kauai and waters just to the south. A couple of rain gauges on the eastern slopes and near Wailua have reported 1 to 1.5 inches of rain in the past 6 hours. In addition, expect spotty afternoon and evening showers, some briefly heavy, across leeward Big Island.
Little change is expected from Tuesday onward. The surface high will settle far northeast of the state and hold into Friday, while the surface trough lingers west of the islands, resulting in breezy easterly trade winds. The nearby upper-level trough will weaken around mid-week, leading to greater stability and supporting a more typical trade shower pattern favoring windward slopes.

Aviation

A fairly stable pattern will remain over the state into next week with some passing high clouds overhead. Moisture embedded within the trade flow will allow for SHRA over windward and mauka areas. VFR conds should prevail over most locations, with MVFR conds possible in any SHRA.
AIRMET Sierra is in effect for mtn obsc for windward Big Island and NE through S portions of Kauai.
AIRMET Tango remains in effect for mod low-level turb downwind of island terrain. This AIRMET will likely remain in effect though much of next week.

Marine

Moderate to strong easterly trades will continue through the week as the surface ridge remains positioned north of the state. The strongest winds are expected over the windier waters around Maui County and the Big Island, supporting the Small Craft Advisory. The lightest winds are anticipated over the Kauai waters, fluctuating between east and east-southeast over the next few days due to a persistent surface trough to the west.
Surf along exposed south-facing shores will remain small throughout much of the week, mainly due to a combination of background south-southwest and southeast swell energy. An upward trend is expected from Friday through the first week of June due to an active pattern unfolding within our swell window near New Zealand.
Altimeter and ASCAT passes over the past 24 hours reflected the potential for next weekend, showing a broad swath of gales with seas up to 30 feet focused at the state within the 190-200 degree directional bands. This will mark the beginning of a long-lived event with additional reinforcements expected within the same area over the next several days.
Surf along exposed east-facing shores will remain small and choppy throughout the week as the trades persist.
Surf along exposed north-facing shores may increase slightly later today through Monday due to a small, medium-period northwest swell expected. Otherwise, summertime conditions are anticipated with minimal surf expected this week.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 PM HST Monday for Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

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Data Courtesy of NOAA.gov