Hilo

Tonight: Partly cloudy with isolated showers. Lows 56 to 65 near the shore to 44 to 52 at 4000 feet. North winds up to 15 mph. Chance of rain 20 percent.

Martin Luther King Jr Day: Mostly sunny with isolated showers. Highs 73 to 79 near the shore to 60 to 66 at 4000 feet. North winds up to 15 mph. Chance of rain 20 percent.

Monday Night: Partly cloudy with scattered showers. Lows 56 to 65 near the shore to 46 to 53 at 4000 feet. North winds up to 10 mph. Chance of rain 40 percent.

Kona

Tonight: Partly cloudy. Lows around 68 near the shore to 41 to 48 near 5000 feet. Light winds.

Martin Luther King Jr Day: Mostly sunny with isolated showers. Highs 78 to 83 near the shore to around 64 near 5000 feet. Southeast winds up to 10 mph shifting to the west in the afternoon. Chance of rain 20 percent.

Monday Night: Partly cloudy with isolated showers. Lows around 68 near the shore to 41 to 47 near 5000 feet. Light winds. Chance of rain 20 percent.

Waimea

Tonight: Breezy. Partly cloudy with isolated showers. Lows 56 to 67 near the shore to 48 to 56 near 3000 feet. East winds 10 to 20 mph decreasing to up to 15 mph after midnight. Chance of rain 20 percent.

Martin Luther King Jr Day: Breezy. Mostly sunny with isolated showers. Highs around 75 near the shore to 65 to 74 near 3000 feet. East winds up to 20 mph. Chance of rain 20 percent.

Monday Night: Partly cloudy with isolated showers. Lows 56 to 67 near the shore to 49 to 56 near 3000 feet. East winds up to 10 mph. Chance of rain 20 percent.

Kohala

Tonight: Breezy. Partly cloudy with isolated showers. Lows 56 to 67 near the shore to 48 to 56 near 3000 feet. East winds 10 to 20 mph decreasing to up to 15 mph after midnight. Chance of rain 20 percent.

Martin Luther King Jr Day: Breezy. Mostly sunny with isolated showers. Highs around 75 near the shore to 65 to 74 near 3000 feet. East winds up to 20 mph. Chance of rain 20 percent.

Monday Night: Partly cloudy with isolated showers. Lows 56 to 67 near the shore to 49 to 56 near 3000 feet. East winds up to 10 mph. Chance of rain 20 percent.

South Big Island

Tonight: Partly cloudy. Lows around 69 near the shore to around 48 near 5000 feet. Northeast winds up to 15 mph in the evening becoming light.

Martin Luther King Jr Day: Mostly sunny. Isolated showers in the afternoon. Highs around 80 near the shore to around 64 near 5000 feet. Northeast winds up to 10 mph shifting to the south in the afternoon. Chance of rain 20 percent.

Monday Night: Partly cloudy. Isolated showers in the evening. Lows around 69 near the shore to around 48 near 5000 feet. Light winds. Chance of rain 20 percent.

Puna

Tonight: Partly cloudy with isolated showers. Lows 56 to 65 near the shore to 44 to 52 at 4000 feet. North winds up to 15 mph. Chance of rain 20 percent.

Martin Luther King Jr Day: Mostly sunny with isolated showers. Highs 73 to 79 near the shore to 60 to 66 at 4000 feet. North winds up to 15 mph. Chance of rain 20 percent.

Monday Night: Partly cloudy with scattered showers. Lows 56 to 65 near the shore to 46 to 53 at 4000 feet. North winds up to 10 mph. Chance of rain 40 percent.

Waikoloa

Tonight: Mostly clear. Breezy. Lows 65 to 71 near the shore to 44 to 50 above 4000 feet. East winds up to 20 mph.

Martin Luther King Jr Day: Sunny and breezy. Highs 79 to 84 near the shore to 63 to 68 above 4000 feet. East winds up to 20 mph shifting to the north in the afternoon.

Monday Night: Mostly clear. Lows 65 to 70 near the shore to 44 to 50 above 4000 feet. Light winds.

Detailed Forecast

Synopsis

Mostly dry and stable conditions will continue to persist through Tuesday across the state. A change in weather pattern is expected mid week as a front moves through the state. Although there is still a fair amount of uncertainty regarding the strength of the front, the threat for gusty southwest winds with moderate to locally heavy rain will begin to increase Wednesday into Thursday.

Discussion

Hilo and Lihue soundings show a stable and dry airmass with precipitable water values of less an 1.0 inch and a strong inversion at roughly 4500-5000 ft this afternoon. Rainfall totals over the past 24 hours have been nearly nonexistent due to the post-frontal dry airmass. We should continue to see stable and dry conditions through Tuesday. The one exception is around mid day Monday into Monday evening, when a band of cumulus clouds is expected to move in from the north and could produce a few light sprinkles over windward and mauka areas. This band of cumulus clouds is seen on satellite and is currently located near 25N. Starting Tuesday, trade winds will weaken due to a developing area of low pressure northwest of the state.
Both the GFS and ECMWF models are in good agreement with the synoptic pattern of an upper level trough moving through the state Wednesday and eventually becoming a cut off low centered north of the state Thursday through rest of the week. The general pattern is for a front to move west to east across the state Wednesday into Thursday with gusty southwest winds and showers and possibly thunderstorms ahead of the front. There is still quite a bit of uncertainty regarding the strength of the front with the ECMWF showing stronger solution with more instability, which will increase the threat for thunderstorms and flash flooding. With the ensemble members showing a solution closer to the ECMWF, the forecast has been nudged toward the ECMWF solution.
Starting Friday, weather conditions should generally improve across the state as the upper level low lifts further north and away from the state. Winds will likely be light or remain out of the westerly direction with some scattered showers still possible.

Aviation

Moderate to locally breezy northeast trades will continue through tonight, then slowly ease through Monday night. VFR conditions will prevail, with scattered low clouds and isolated light showers over windward areas. No AIRMETs are in effect nor expected through Monday.

Marine

A high pressure system passing just north of the Hawaiian Islands will keep moderate trade winds in the forecast into Monday. A shallow cold front approaching and then moving into the islands on Tuesday and Wednesday will produce more variable winds along and ahead of the frontal band. Northwesterly winds will build in behind the front as it passes through each island.
The current long period northwest swell will decline tonight. Surf heights along north and west facing shores will steadily decrease in line with this decreasing swell energy. The High Surf Advisory along exposed north and west facing shores remains in effect through tonight. Surf heights are expected to fall below advisory thresholds by morning. The next northwest swell may produce advisory level surf along exposed north and west facing shores from Tuesday into Wednesday, then slowly fade through the end of the week.
East facing shore surf will remain choppy the next few days as the trades build, and background south swell will keep surf small on south facing shores through the coming week.
The Small Craft Advisory (SCA) remains in effect for waters windier waters around Maui and the Big Island.

Fire weather

Dry conditions will continue to persist through Tuesday, but the trade winds should remain at moderate to locally breezy at best then weaken Tuesday into Wednesday. Starting Wednesday, a front should move down the island chain through Thursday, which could produce some much needed rainfall for some leeward areas. Critical fire weather conditions are not expected this week.

HFO Watches/Warnings/Advisories

High Surf Advisory until 6 AM HST Monday for Niihau, Kauai Leeward, Waianae Coast, Oahu North Shore, Maui Windward West, Kauai North, Molokai Windward, Molokai North, Molokai West, Maui Central Valley North, Windward Haleakala.
Small Craft Advisory until 6 AM HST Monday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Southeast Waters.

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Data Courtesy of NOAA.gov