Photo Credit: Pamela Goguen Lynch

West Side

Today: Mostly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 72 to 80. Northeast winds 20 to 25 mph. Chance of rain 40 percent.

Tonight: Breezy. Partly cloudy with scattered showers. Lows 63 to 70. East winds 15 to 25 mph. Chance of rain 50 percent.

Friday: Mostly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 72 to 80. Northeast winds 15 to 25 mph. Chance of rain 30 percent.

South Side

Today: Mostly sunny. Breezy. Highs around 82. Northeast winds 10 to 25 mph.

Tonight: Partly cloudy. Breezy. Isolated showers after midnight. Lows 61 to 69. Northeast winds up to 25 mph becoming 10 to 20 mph after midnight. Chance of rain 20 percent.

Friday: Mostly sunny. Breezy. Highs around 82. Northeast winds 10 to 25 mph.

North Shore

Today: Mostly cloudy. Breezy. Showers likely in the morning, then scattered showers in the afternoon. Highs 71 to 78 near the shore to around 59 near 5000 feet. East winds 10 to 25 mph. Chance of rain 70 percent.

Tonight: Breezy. Mostly cloudy with showers likely. Lows around 66 near the shore to 45 to 50 near 5000 feet. East winds 10 to 20 mph. Chance of rain 70 percent.

Friday: Partly sunny. Breezy. Showers likely in the morning, then scattered showers in the afternoon. Highs 71 to 78 near the shore to around 60 near 5000 feet. East winds 10 to 20 mph. Chance of rain 70 percent.

Central Maui

Today: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 76 to 81. Northeast winds 10 to 25 mph. Chance of rain 50 percent.

Tonight: Breezy. Partly cloudy with isolated showers. Lows 62 to 67. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Friday: Breezy. Mostly sunny with isolated showers. Highs 76 to 82. Northeast winds 10 to 25 mph. Chance of rain 20 percent.

Upcountry

Today: Breezy. Mostly sunny with scattered showers. Highs around 55 at the visitor center to around 51 at the summit. East winds 10 to 20 mph. Chance of rain 50 percent.

Tonight: Breezy. Partly cloudy with scattered showers. Lows around 43 at the visitor center to around 40 at the summit. East winds up to 15 mph increasing to 10 to 20 mph after midnight. Chance of rain 50 percent.

Friday: Mostly sunny. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 56 at the visitor center to around 51 at the summit. East winds 10 to 15 mph. Chance of rain 50 percent.

East Maui

Today: Mostly cloudy. Breezy. Showers likely in the morning, then scattered showers in the afternoon. Highs 71 to 78 near the shore to around 59 near 5000 feet. East winds 10 to 25 mph. Chance of rain 70 percent.

Tonight: Breezy. Mostly cloudy with showers likely. Lows around 66 near the shore to 45 to 50 near 5000 feet. East winds 10 to 20 mph. Chance of rain 70 percent.

Friday: Partly sunny. Breezy. Showers likely in the morning, then scattered showers in the afternoon. Highs 71 to 78 near the shore to around 60 near 5000 feet. East winds 10 to 20 mph. Chance of rain 70 percent.

Lanai City

Today: Mostly sunny. Breezy. Isolated showers in the afternoon. Highs 69 to 77. Northeast winds 15 to 25 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Breezy. Lows 58 to 63. Northeast winds 10 to 20 mph.

Friday: Mostly sunny. Breezy. Isolated showers in the afternoon. Highs 69 to 77. Northeast winds 10 to 25 mph. Chance of rain 20 percent.

Kaunakakai

Today: Breezy. Mostly sunny with isolated showers. Highs 62 to 82. East winds 20 to 25 mph. Chance of rain 20 percent.

Tonight: Breezy. Partly cloudy with isolated showers. Lows 54 to 70. East winds 15 to 20 mph. Chance of rain 20 percent.

Friday: Mostly sunny. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 63 to 83. East winds 15 to 25 mph. Chance of rain 40 percent.

Detailed Forecast

Synopsis

Breezy trade winds will weaken somewhat by Christmas Day, then strengthen again from Sunday into next week. The trade winds will deliver passing low clouds and a few brief showers to windward areas, occasionally spreading leeward. A kona low developing well west of the islands this weekend may bring the potential for increased showers from Sunday into next week, and may turn winds to the southeast for a day or two.

Discussion

Strong high pressure far N of the islands will change little through the period, supporting locally breezy trade winds, but some weakening of the local pressure gradient on Christmas Day is expected to lead to a modest decrease in trade wind speeds. A kona low developing about 500-700 miles NW of the islands over the weekend will likely lead to a tightening of the gradient from Sunday into next week, with E to SE winds becoming locally strong in response. The island atmosphere will remain relatively unstable through the weekend as a mid-level trough lingers N of the islands, but with limited low-level moisture arriving on the trades, only brief windward showers are anticipated through Saturday, with some afternoon showers over the Kona slopes. Increased low-level convergence E of the kona low may bring an increase in shower coverage to Kauai on Sunday, potentially spreading to the other islands through the middle part of next week. With E to SE winds blowing, any increased rainfall will be most likely to affect windward areas.

Aviation

Moderate to breezy trade winds continue today as a high pressure system remains locked in place far north of the Hawaii region. An upper level disturbance will keep periods of showers in the forecast through the rest of the week. MVFR conditions are possible over north through east sections of the eastern islands, mainly in the early morning hours. Wind speeds show decreasing trends and AIRMET Tango for moderate low level turbulence was cancelled this morning.
AIRMET Sierra for mountain obscuration remains in effect over Maui and the Big Island this morning. These low cloud ceilings will likely continue into the morning hours.

Marine

A broad 1040 mb surface high located far north of the islands will maintain fresh to strong trade winds through today where a Small Craft Advisory (SCA) remains posted for all Hawaiian waters. With the slightly lighter trades, the SCA is likely to be extended into Friday, but the marine zones affected will be scaled down to the typically windy areas of Maui County and waters south of the Big Island. Between Sunday and Monday, the trade winds will be shifting to the east and southeast while strengthening to moderate to strong area-wide, leading to a possible expansion of the SCA covering most Hawaiian waters.
The combination of an elevated north-northeast swell and locally generated trade wind swell has resulted in rough seas and elevated surf. A High Surf Advisory (HSA) remains in effect for the east facing shores through late this afternoon, with the possibility of an extension through tonight. The latest PacIOOS buoy reports from Hilo and Hanalei indicate that a declining trend has begun, down a foot each in both the swell and combined seas, and period shorter at 11 to 12 seconds. Both swells are expected to lower a little more then hold at moderate levels into early next week. This moderate swell translate to moderate surf along north and east facing shores. There could be a slight rise in the surf along the east facing shores on Monday, due to the boost in the east to southeast winds. This boost may bring surf to near advisory level once again along the east facing shores. Between Monday and Thursday, the west facing shores can expect some small to moderate surf from a series of west- northwest pulses.
Instability from an upper level trough will maintain thunderstorms across the southern offshore waters through tonight. After a lull on Saturday, the threat of thunderstorms returns to the western offshore and near-shore waters of Kauai County Sunday through Monday.

HFO Watches/Warnings/Advisories

High Surf Advisory until 6 PM HST this evening for East facing shores of Kauai Oahu Molokai Maui and the Big Island.
Small Craft Advisory until 6 PM HST this evening for all Hawaiian waters.

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Data Courtesy of NOAA.gov