Photo Credit: James Grenz

Hilo

Today: Mostly cloudy. Occasional showers in the morning, then numerous showers in the afternoon. Highs 78 to 84 near the shore to 62 to 69 at 4000 feet. Northeast winds 10 to 15 mph. Chance of rain 90 percent.

Tonight: Occasional showers. Lows 63 to 70 near the shore to 53 to 58 at 4000 feet. East winds up to 10 mph. Chance of rain near 100 percent.

Sunday: Mostly cloudy with numerous showers. Highs 79 to 84 near the shore to 64 to 71 at 4000 feet. East winds 10 to 15 mph. Chance of rain 70 percent.

Kona

Today: Mostly sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs around 86 near the shore to around 68 near 5000 feet. South winds up to 10 mph shifting to the west around 10 mph in the afternoon. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers in the evening, then partly cloudy after midnight. Lows around 72 near the shore to 46 to 53 near 5000 feet. Southeast winds up to 10 mph. Chance of rain 50 percent.

Sunday: Mostly sunny. Scattered showers in the afternoon. Highs around 87 near the shore to around 69 near 5000 feet. Southwest winds up to 10 mph. Chance of rain 50 percent.

Waimea

Today: Breezy. Partly sunny with scattered showers. Highs around 79 near the shore to 67 to 77 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 62 to 71 near the shore to 52 to 61 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Sunday: Breezy. Partly sunny with scattered showers. Highs around 80 near the shore to 69 to 78 near 3000 feet. East winds 10 to 25 mph with gusts to 45 mph. Chance of rain 50 percent.

Kohala

Today: Breezy. Partly sunny with scattered showers. Highs around 79 near the shore to 67 to 77 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 62 to 71 near the shore to 52 to 61 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Sunday: Breezy. Partly sunny with scattered showers. Highs around 80 near the shore to 69 to 78 near 3000 feet. East winds 10 to 25 mph with gusts to 45 mph. Chance of rain 50 percent.

South Big Island

Today: Breezy. Mostly sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs around 86 near the shore to around 67 near 5000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Tonight: Partly cloudy. Breezy. Lows around 73 near the shore to around 49 near 5000 feet. East winds 10 to 20 mph.

Sunday: Sunny and breezy. Isolated showers in the afternoon. Highs around 86 near the shore to around 69 near 5000 feet. East winds 10 to 25 mph. Chance of rain 20 percent.

Puna

Today: Mostly cloudy. Occasional showers in the morning, then numerous showers in the afternoon. Highs 78 to 84 near the shore to 62 to 69 at 4000 feet. Northeast winds 10 to 15 mph. Chance of rain 90 percent.

Tonight: Occasional showers. Lows 63 to 70 near the shore to 53 to 58 at 4000 feet. East winds up to 10 mph. Chance of rain near 100 percent.

Sunday: Mostly cloudy with numerous showers. Highs 79 to 84 near the shore to 64 to 71 at 4000 feet. East winds 10 to 15 mph. Chance of rain 70 percent.

Waikoloa

Today: Mostly sunny. Breezy. Isolated showers in the afternoon. Highs around 85 near the shore to 64 to 71 above 4000 feet. East winds 10 to 20 mph shifting to the northeast in the afternoon. Chance of rain 20 percent.

Tonight: Mostly clear. Breezy. Lows 70 to 75 near the shore to 48 to 54 above 4000 feet. East winds 10 to 20 mph.

Sunday: Sunny. Highs 83 to 88 near the shore to 64 to 73 above 4000 feet. Northeast winds 10 to 15 mph.

Detailed Forecast

Synopsis

Breezy trade winds will continue through the weekend, with some areas seeing stronger winds late Sunday. Showers will remain focused over the windward and mountain areas, mostly overnight and during the morning hours. Strong northeasterly trade winds are expected Monday night and Tuesday as a cold front brings another period of mainly windward showers. A cool and somewhat drier air mass will move over the islands after the front passes, with lighter winds and a warming trend expected later in the week.

Discussion

Have made some changes to the forecast but the over all forecast is generally the same. The PoP/Wx/Sky grids were nudged to the National Blend of Models which trended the forecast a bit wetter this weekend. Based on satellite data showing showery low clouds upstream of the islands, felt trending towards the NBM was warranted. With trade winds continuing, most of these showers will remain focused over windward and mountain areas.
Otherwise, the forecast philosophy remains the same. The high pressure system far to the northwest of the islands will track to the southeast and position itself north of the islands. A deep-layer low developing to the northeast of the islands will bring a shallow front to the islands which will increase rainfall particularly over the windward and mountain areas, however a few leeward showers will be possible.
Behind the front, winds will get another boost and a relatively dry air mass will settle in over the islands for a day or two. We can expect lower dewpoints that will make it feel seasonably cool. Wind gusts approaching 50 mph will likely prompt a Wind Advisory for many locations. With leeward areas not expected to get much in the way of rainfall between now and then, the strong winds and dry air mass will bring the potential for an increased risk of fire danger.
Wind speeds will gradually ease during the second half of next week as the high moves further to the southeast and weakens. Long range guidance indicates the potential for trade winds to break down in just over a week.

Aviation

Moderate to locally breezy trade winds will carry bands of cumulus and weak showers towards the Islands. Windward sides of the islands will be primarily impacted, with occasional spill-over showers blowing over to leeward sides of the smaller islands.
AIRMET Tango is posted for occasional moderate turbulence over and to the lee of mountains for all islands due to the breezy winds.
AIRMET Sierra is in effect for mountain obscuration along windward slopes of Oahu and Kauai. Conditions are expected to develop by morning and persist through midday. Elsewhere, VFR conditions will prevail.

Marine

A high pressure ridge north of the Hawaii region will keep fresh to strong trade winds in place across the area. A strong high center building into the northern Central Pacific basin will strengthen the trades into the strong to near gale range by Sunday. Further strengthening of the trades and rising seas are expected following the passage of a cold front Monday night into Tuesday. Seas are forecast to build to 10 feet or greater across all marine zones and gale force winds are likely across at least the windier areas around Maui and the Big Island from Tuesday through Wednesday. A Small Craft Advisory (SCA) remains in effect for most eastern coastal waters and channels through the weekend. This SCA will likely expand to most coastal waters and channels from Monday through Wednesday.
A series of small, medium period north and northwest swells will keep some modest surf in place along north and west facing shores through Sunday. The northwest swell energy will decline Monday, with little to no northwest swell expected Tuesday through Thursday with a small medium period northwest swell arriving late Friday.
Surf along east facing shores will remain choppy through Monday. Strengthening trades in combination with the arrival of a large northeast swell will give east shore surf a sizable boost, likely to advisory levels, from Monday night through Thursday. The trade wind swell will also wrap into exposed north facing shores.
Small mainly background south swell energy is expected through middle of next week. A small long period south swell could boost south shore surf up from Thursday night through Friday.

HFO Watches/Warnings/Advisories

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

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Data Courtesy of NOAA.gov