Hilo

Today: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 82 to 87 near the shore to 69 to 75 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 67 to 73 near the shore to around 58 at 4000 feet. Northwest winds up to 15 mph. Chance of rain 50 percent.

Saturday: Partly sunny in the morning then becoming mostly sunny. Scattered showers. Highs 82 to 87 near the shore to 69 to 75 at 4000 feet. Northeast winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 50 percent.

Kona

Today: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 87 near the shore to around 71 near 5000 feet. Light winds. Chance of rain 40 percent.

Tonight: Partly cloudy. Isolated showers after midnight. Lows around 74 near the shore to around 55 near 5000 feet. Light winds. Chance of rain 20 percent.

Saturday: Mostly sunny. Isolated showers in the afternoon. Highs 85 to 90 near the shore to around 71 near 5000 feet. Light winds. Chance of rain 20 percent.

Waimea

Today: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs around 82 near the shore to 72 to 80 near 3000 feet. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 50 percent.

Tonight: Breezy. Partly cloudy with isolated showers. Lows 67 to 72 near the shore to 58 to 65 near 3000 feet. East winds 10 to 20 mph. Chance of rain 20 percent.

Saturday: Breezy. Mostly sunny with isolated showers. Highs around 82 near the shore to 73 to 80 near 3000 feet. East winds 10 to 25 mph. Chance of rain 20 percent.

Kohala

Today: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs around 82 near the shore to 72 to 80 near 3000 feet. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 50 percent.

Tonight: Breezy. Partly cloudy with isolated showers. Lows 67 to 72 near the shore to 58 to 65 near 3000 feet. East winds 10 to 20 mph. Chance of rain 20 percent.

Saturday: Breezy. Mostly sunny with isolated showers. Highs around 82 near the shore to 73 to 80 near 3000 feet. East winds 10 to 25 mph. Chance of rain 20 percent.

South Big Island

Today: Mostly sunny. Breezy. Isolated showers in the morning. Highs around 87 near the shore to around 73 near 5000 feet. East winds up to 25 mph. Chance of rain 20 percent.

Tonight: Mostly clear. Breezy. Lows around 74 near the shore to around 55 near 5000 feet. Northeast winds up to 20 mph.

Saturday: Sunny. Isolated showers in the afternoon. Highs around 88 near the shore to around 72 near 5000 feet. East winds up to 15 mph. Chance of rain 20 percent.

Puna

Today: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 82 to 87 near the shore to 69 to 75 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 67 to 73 near the shore to around 58 at 4000 feet. Northwest winds up to 15 mph. Chance of rain 50 percent.

Saturday: Partly sunny in the morning then becoming mostly sunny. Scattered showers. Highs 82 to 87 near the shore to 69 to 75 at 4000 feet. Northeast winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 50 percent.

Waikoloa

Today: Mostly sunny. Isolated showers in the morning. Highs around 89 near the shore to 70 to 76 above 4000 feet. Northeast winds up to 15 mph. Chance of rain 20 percent.

Tonight: Mostly clear. Breezy. Lows around 75 near the shore to 54 to 59 above 4000 feet. Southeast winds up to 20 mph.

Saturday: Sunny and breezy. Isolated showers in the afternoon. Highs around 89 near the shore to 71 to 76 above 4000 feet. Northeast winds up to 25 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

A high pressure center far north to northeast of the Hawaii Region will continue to produce moderate to locally breezy trade winds today with slight decreasing trends through Saturday. A passing weak low level trough will enhance showers during the overnight hours through Saturday morning. Two upper level lows moving into position north of the Hawaii region will significantly decrease the wind speeds over the islands from Sunday through Tuesday. Light large scale winds on Monday and Tuesday will allow local scale land and sea breezes to expand in coverage to include most leeward areas. Brief shower trends may increase for the first half of next week due to upper level troughing and island heating.

Discussion

The infra-red satellite imagery this morning over the Hawaii Region shows a weak low level trough moving from east to west across the island chain. Expect Periods of showers along the typical windward, north through east, slopes of each island into the early morning hours. Trade wind inversion heights remain elevated in the 6,000 to 8,000 foot range as shown in this mornings 12Z upper air balloon soundings from Hilo and Lihue. Local radar imagery shows numerous trade wind showers drifting into windward areas (north through east slopes) this morning. These enhanced windward and mountain showers will diminish by late morning and then redevelop later tonight. Leeward areas (south through west slopes) will remain on the dry side with just a few of the stronger windward showers possibly bringing a brief passing shower or two during the early morning hours.
A high pressure system far north to northeast of the Hawaii Region will continue to produce moderate to locally breezy trade winds with slight decreasing wind speed trends through Saturday. A cold air mass moving down the eastern side of this high center will approach Hawaii from Sunday to Monday. This cold air will deepen an upper level low just north of the state, significantly weakening the surface pressure gradient over the islands and producing light and variable winds over the region. In the absence of large scale trade winds, local scale land and sea breezes will expand in coverage from Sunday through Tuesday, producing onshore/upslope winds each afternoon with offshore/downslope winds at night, especially over leeward areas.
Passing windward shower activity will continue for all islands during the overnight to early morning hours through Saturday morning as the low level trough slowly drifts westward through the state. Starting on Sunday, a combination of upper level troughing with island heating and converging sea breeze winds may increase shower potential over the typically drier leeward areas each afternoon from Sunday through Tuesday. Downslope land breeze winds will start after sunset and last through the early morning hours, producing more stable conditions over all island slopes. This land and sea breeze weather pattern will continue at least through Tuesday. Isolated thunderstorms may develop over the upper slopes of the Big Island on Sunday afternoon.
Long range model guidance continue to hint at a slight strengthening of the trade wind speeds on Wednesday. However, we are less certain that the trade winds will come back on time as two surface troughs will linger just north of the islands and once the land and sea breeze pattern is established stronger trade winds are typically needed to break this local scale wind cycle. Model solutions differ on how strong the ridge builds back in north of the island chain for the second half of next week. Returning trade winds on Wednesday will slowly decrease the coverage of leeward afternoon sea breezes, with a gradual increase in trade wind speeds forecast through next week Friday.

Aviation

Moderate to locally breezy trade winds will persist through this evening and then trend weaker for the weekend. A slight uptick in low level moisture is allowing for increased low level clouds and showers early this morning, mainly across windward and mountain areas, but brief spillovers into leeward areas will remain possible. Overall, VFR conditions will prevail with brief periods of MVFR conditions during the overnight and early morning hours.
AIRMET Tango remains in effect for low level turbulence over and downwind of the terrain across all islands. This AIRMET will likely be needed through most of today, but low level turbulence will begin to trend downward as the pressure gradient weakens into the weekend.

Marine

A robust 1029 mb surface high resides well north of the Hawaiian islands and continues to produce fresh to locally strong trade winds across the local waters, though slightly weaker than the previous 24-hours. Thus, the Small Craft Advisory has been reduced to typical windy zones around Maui County and the Big Island. The aforementioned surface high will remain stagnant through Saturday with very little change expected across local waters. Sunday into Monday, a weak trough approaching from the east will pass north of the area and weaken trade flow. Sea breeze development appear likely near the coast during the afternoons on Monday and Tuesday as flow remains light to gentle.
Rough choppy surf along east facing shores will persist for the next several days as the trades remain breezy. Additionally, expect some swell mixed in from former Tropical Cyclone (TC) Irwin through the weekend. Mokapu Point buoy continues to show this energy in the 10 to 12 second bands. Surf heights should stay below the 10 ft (faces) High Surf Advisory (HSA) criteria during the peak of this event today through Saturday. A downward trend is expected Sunday into early next week as the trades weaken.
Surf along south facing shores will remain small through the weekend as overlapping background level long-period southerly pulses move through. A moderate south to south-southwest swell is expected to slowly fill in Monday and peak from Tuesday through Wednesday near HSA levels for south facing shores, then slowly decline through rest of the week.
Surf along exposed north and west facing shores will trend up slightly late Saturday through early next week as a small west- northwest (300-310 degree) swell arrives. This will be in response to a storm-force low (former TC Damrey) racing eastward toward the Date Line from Japan over the past couple of days.

Fire weather

Traditional leeward areas, south through west of island mountains, will see the lowest afternoon minimum RH values in the middle to low 40 percent range lasting through the weekend. Sustained wind speeds will likely approach, yet not exceed Red Flag Warning thresholds in these leeward areas each afternoon through Saturday. Wind speeds will decrease significantly from Sunday through Tuesday with lighter large scale trade winds allowing an expansion of afternoon onshore/upslope sea breezes across most leeward areas. Isolated to scattered slow moving showers may develop each afternoon from Sunday through Tuesday.
Long range model guidance continues to hint at increasing trade wind speed trends starting next week Wednesday. However, there are still two surface troughs lingering just north of the islands that may limit trade wind speeds towards the light to moderate range on Wednesday, with increasing wind speed trends through next week Friday.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 AM HST Saturday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

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Data Courtesy of NOAA.gov