Hilo

Today: Cloudy with showers likely in the morning, then partly sunny with scattered showers in the afternoon. Highs 77 to 84 near the shore to 63 to 70 at 4000 feet. North winds up to 15 mph shifting to the northeast in the afternoon. Chance of rain 70 percent.

Tonight: Mostly cloudy with showers likely. Lows 63 to 70 near the shore to 53 to 58 at 4000 feet. North winds up to 15 mph. Chance of rain 70 percent.

Tuesday: Partly sunny. Showers likely in the morning, then scattered showers in the afternoon. Highs 79 to 84 near the shore to 64 to 70 at 4000 feet. Northeast winds 10 to 15 mph shifting to the east in the afternoon. Chance of rain 70 percent.

Kona

Today: Sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs 83 to 89 near the shore to around 70 near 5000 feet. West winds up to 10 mph. Chance of rain 40 percent.

Tonight: Partly cloudy. Isolated showers in the evening. Lows 69 to 74 near the shore to 51 to 57 near 5000 feet. Light winds. Chance of rain 20 percent.

Tuesday: Mostly sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs around 85 near the shore to around 68 near 5000 feet. Light winds becoming northwest up to 10 mph in the afternoon. Chance of rain 20 percent.

Waimea

Today: Breezy. Partly sunny with scattered showers. Highs 64 to 85. East winds 10 to 25 mph. Chance of rain 50 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 63 to 70 near the shore to 54 to 63 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Tuesday: Partly sunny with scattered showers. Highs 65 to 84. East winds 10 to 15 mph. Chance of rain 50 percent.

Kohala

Today: Breezy. Partly sunny with scattered showers. Highs 64 to 85. East winds 10 to 25 mph. Chance of rain 50 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 63 to 70 near the shore to 54 to 63 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Tuesday: Partly sunny with scattered showers. Highs 65 to 84. East winds 10 to 15 mph. Chance of rain 50 percent.

South Big Island

Today: Breezy. Sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs around 84 near the shore to around 67 near 5000 feet. East winds up to 25 mph. Chance of rain 30 percent.

Tonight: Partly cloudy. Breezy. Lows around 72 near the shore to around 53 near 5000 feet. Northeast winds 10 to 20 mph.

Tuesday: Breezy. Mostly sunny in the morning, then partly sunny with isolated 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 20 percent.

Puna

Today: Cloudy with showers likely in the morning, then partly sunny with scattered showers in the afternoon. Highs 77 to 84 near the shore to 63 to 70 at 4000 feet. North winds up to 15 mph shifting to the northeast in the afternoon. Chance of rain 70 percent.

Tonight: Mostly cloudy with showers likely. Lows 63 to 70 near the shore to 53 to 58 at 4000 feet. North winds up to 15 mph. Chance of rain 70 percent.

Tuesday: Partly sunny. Showers likely in the morning, then scattered showers in the afternoon. Highs 79 to 84 near the shore to 64 to 70 at 4000 feet. Northeast winds 10 to 15 mph shifting to the east in the afternoon. Chance of rain 70 percent.

Waikoloa

Today: Sunny and breezy. Highs 83 to 91 near the shore to 69 to 75 above 4000 feet. Northeast winds up to 25 mph.

Tonight: Mostly clear. Lows 70 to 75 near the shore to 50 to 56 above 4000 feet. East winds up to 15 mph.

Tuesday: Mostly sunny. Isolated showers in the afternoon. Highs 83 to 89 near the shore to 65 to 72 above 4000 feet. Northeast winds up to 10 mph in the morning becoming light. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Breezy trades will weaken to moderate from Wednesday onward and will remain on the drier side throughout this time. The best opportunities for rain will be over windward and mauka areas during the overnight and early morning hours.

Discussion

A compact upper-level shortwave evident on water vapor imagery is approaching the islands from the north this morning and is modeled to become increasingly closed off from the westerlies as it approaches the state during the next 18 hours or so. A noticeable reduction of trade winds into the moderate category is then expected from Wednesday onward as the upper low eases the local pressure gradient and spends the remainder of the forecast period advancing from east to west over the area. Although the inversion will remain slightly elevated or weaker than normal at times during this period, indications from upstream satellite and the latest model solutions are that limited moisture availability will still support relatively dry trades for at least the next several days. Some increase in cirrus coverage is probable by the end of the week as the strengthening southwesterly upper jet funnels convective debris from the ITCZ over area skies.

Aviation

Surface high pressure N of the islands will produce breezy to locally strong ENE trade winds, and AIRMET Tango for low level turbulence over and downwind of terrain on all islands will remain posted.
Moisture immediately upstream is relatively sparse, but still contains a sufficient amount of low clouds to deliver a few showers to windward coasts and slopes, producing isolated MVFR VIS/CIG in SHRA. VFR conditions will prevail over most leeward areas, but afternoon clouds on the leeward slopes of the Big Island will likely produce isolated MVFR conditions. An area of increased low-level moisture further upstream may arrive later today, bringing the potential for increased windward shower coverage.

Marine

A fairly tight pressure gradient, generated by high pressure far north of the area in combination with a surface trough moving west to the south of the island chain, is helping to produce trade winds in the moderate to breezy range over coastal waters. This will persist into Tuesday. Wind speeds may slow a bit late Tuesday through Thursday as high pressure north of the islands weakens. The Small Craft Advisory (SCA), that had been covering most of the Hawaiian coastal waters, has been reduced in area to the typically windier waters around Maui County and the Big Island as the surface trough passes slowly west of the area. The SCA will likely be dropped everywhere Tuesday into Thursday as winds ease further.
The north-northwest swell will continue to slowly lower, with north shore surf dropping through the day. A small north swell will build in Tuesday into Wednesday with a small bump in surf heights expected along north facing shores. The south swell will fade to background level surf heights through at least Wednesday. The trade wind swell will gradually decrease today and Tuesday. East shore surf will increase back to near average heights on Thursday or Friday as the trades increase once more.

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

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Data Courtesy of NOAA.gov