Hilo

Tonight: Mostly cloudy with numerous showers. Lows 58 to 66 near the shore to 46 to 53 at 4000 feet. Northwest winds up to 10 mph. Chance of rain 70 percent.

Saturday: Mostly cloudy with numerous showers. Highs 75 to 80 near the shore to 60 to 65 at 4000 feet. North winds up to 15 mph shifting to the northeast in the afternoon. Chance of rain 70 percent.

Saturday Night: Mostly cloudy with numerous showers. Lows 58 to 66 near the shore to 46 to 53 at 4000 feet. North winds up to 10 mph. Chance of rain 60 percent.

Kona

Tonight: Mostly clear. Haze. Lows around 68 near the shore to 41 to 47 near 5000 feet. Light winds.

Saturday: Sunny in the morning, then partly sunny with scattered showers and isolated thunderstorms in the afternoon. Haze through the day. Highs 80 to 85 near the shore to around 64 near 5000 feet. Southeast winds up to 10 mph shifting to the north in the afternoon. Chance of rain 50 percent.

Saturday Night: Mostly clear. Haze. Lows around 68 near the shore to 40 to 47 near 5000 feet. Light winds.

Waimea

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 59 to 68 near the shore to 51 to 58 near 3000 feet. East winds 10 to 20 mph decreasing to up to 20 mph after midnight. Gusts up to 40 mph. Chance of rain 50 percent.

Saturday: Partly sunny in the morning then becoming mostly sunny. Breezy. Scattered showers. Highs around 76 near the shore to 66 to 75 near 3000 feet. East winds 10 to 25 mph. Chance of rain 50 percent.

Saturday Night: Breezy. Partly cloudy with isolated showers. Lows 58 to 68 near the shore to 50 to 58 near 3000 feet. East winds 10 to 20 mph. Chance of rain 20 percent.

Kohala

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 59 to 68 near the shore to 51 to 58 near 3000 feet. East winds 10 to 20 mph decreasing to up to 20 mph after midnight. Gusts up to 40 mph. Chance of rain 50 percent.

Saturday: Partly sunny in the morning then becoming mostly sunny. Breezy. Scattered showers. Highs around 76 near the shore to 66 to 75 near 3000 feet. East winds 10 to 25 mph. Chance of rain 50 percent.

Saturday Night: Breezy. Partly cloudy with isolated showers. Lows 58 to 68 near the shore to 50 to 58 near 3000 feet. East winds 10 to 20 mph. Chance of rain 20 percent.

South Big Island

Tonight: Mostly clear. Breezy and haze. Lows around 70 near the shore to around 48 near 5000 feet. Northeast winds 10 to 20 mph.

Saturday: Mostly sunny. Breezy. Haze through the day. Scattered showers and isolated thunderstorms in the afternoon. Highs around 82 near the shore to around 65 near 5000 feet. Northeast winds 10 to 25 mph shifting to the east up to 25 mph in the afternoon. Chance of rain 50 percent.

Saturday Night: Mostly clear. Haze. Lows around 70 near the shore to around 48 near 5000 feet. Northeast winds 10 to 15 mph.

Puna

Tonight: Mostly cloudy with numerous showers. Lows 58 to 66 near the shore to 46 to 53 at 4000 feet. Northwest winds up to 10 mph. Chance of rain 70 percent.

Saturday: Mostly cloudy with numerous showers. Highs 75 to 80 near the shore to 60 to 65 at 4000 feet. North winds up to 15 mph shifting to the northeast in the afternoon. Chance of rain 70 percent.

Saturday Night: Mostly cloudy with numerous showers. Lows 58 to 66 near the shore to 46 to 53 at 4000 feet. North winds up to 10 mph. Chance of rain 60 percent.

Waikoloa

Tonight: Mostly clear. Breezy. Lows 66 to 72 near the shore to 45 to 50 above 4000 feet. Southeast winds up to 25 mph.

Saturday: Sunny and breezy. Isolated showers in the afternoon. Highs 80 to 86 near the shore to 62 to 68 above 4000 feet. East winds up to 25 mph. Chance of rain 20 percent.

Saturday Night: Mostly clear. Lows 66 to 72 near the shore to 43 to 49 above 4000 feet. East winds up to 10 mph.

Detailed Forecast

Synopsis

Moderate to locally breezy trades will prevail through the weekend before weakening early next week as a decaying cold front approaches the area. Showers will mainly focus over windward and mauka areas during this time.

Discussion

Convective cloud debris from this morning's activity over Windward Big Island delayed the onset of destabilization this afternoon with little more than a couple of isolated heavy showers through 2pm HST. Save for cloud cover, the thermodynamic environment has only become more conducive to deep convection since this morning with 500mb temps presently around -14C and steep mid-level lapse rates well in excess of 7C/km parked over the eastern end of the state. As clouds have thinned late this afternoon, convection is finally increasing in coverage along the convergent sea breeze boundary which is anchored over downslope portions of the Kona Districts. Expect a nuisance flooding threat to persist for the remainder of the day along with isolated thunderstorms capable of producing wind gusts in the 40-50 mph range. The threat for flash flooding is non-zero, but downslope convection remains poorly organized and relatively shallow at this time with any thunderstorm activity still confined to upslope portions of the North Kona District where cloud cover has been comparatively less. It appears likely that this will remain the case for the next couple of hours before convective activity diminishes.
Active subsidence associated with building mid-level ridging will spread across the area from west to east tonight into early next week gradually bringing a return to stable trades. As it stands, the existing moisture field does not appear deep enough to capitalize on resident instability anyway, so nothing more than an isolated heavy shower is expected. The potential exception is Leeward Big Island where instability is unlikely to be hindered by cloud cover on Saturday. For this reason, added thunder to Leeward Big Island zones tomorrow afternoon as the cold pool aloft lingers over the eastern end of the state and undergoes little in the way of modification. Trades weaken early next week as the tail end of a mid-latitude trough digs toward the islands ushering a weakening cold front into the forecast area.

Aviation

The potential for localized heavy showers and thunderstorms will continue over the eastern end of the state through Saturday. The most likely location for this activity will be over the Big Island leeward slopes through this evening and again Saturday afternoon. Otherwise, moderate to locally breezy trades will continue, with scattered showers moving into windward areas and a shower or two pushed over to leeward sides at times.
AIRMET Sierra for mountain obscuration has been cancelled for windward areas of the Big Island.
AIRMET Tango remains in effect for low level turbulence associated with the breezy trade winds.

Marine

Surface high pressure to the north will drive moderate to locally strong trades through the weekend. The trades may ease up slightly early next week as the ridge weakens. An upper level trough will enhance some of the incoming showers from the east. A Small Craft Advisory (SCA) is in effect for the typically windy waters around Maui and the Big island through 6 pm HST Saturday.
The current northwest swell will gradually decline tonight. The High Surf Advisory (HSA) for exposed north and west facing shores has been cancelled, however, near advisory level will continue through the late afternoon and early evening before falling overnight.
A new long-period northwest swell will arrive late Saturday and Saturday night, peak Sunday into Sunday night, then lower on Monday. This swell will give another boost to surf along north and west facing shores, but will likely remain below advisory levels. A pair of overlapping northwest swells will then move through early next week, with the first arriving early Monday, peaking late Monday and Monday night. The second will build Monday night, peak Tuesday then gradually decline through next Thursday. These overlapping swells may bring another round of advisory level surf to most north and west facing shores Monday afternoon through Tuesday night.
East shore surf not exposed to the series of northwest swells will gradually rise through Saturday as the trades return over and upstream of the islands. Surf along east facing shores will then hold relatively steady Sunday, then lower a bit Monday through Wednesday as the trades ease slightly. East shore surf could trend lower again late next week as an approaching front disrupts the trades over the islands.
South shore surf will remain very small through the middle of next week. An out of season long-period south swell may move through the islands late next week, bringing a sizable boost to south shore surf.

Fire weather

No critical fire weather conditions expected through the forecast period.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 PM HST this evening for Kauai Northwest Waters, Kauai Windward Waters, Kauai Leeward Waters, Kauai Channel, Oahu Windward Waters, Kaiwi Channel, Maui County Windward Waters, Big Island Windward Waters.
Small Craft Advisory until 6 PM 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