Hilo

Today: Partly sunny with scattered showers. Highs 81 to 86 near the shore to around 71 at 4000 feet. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Showers likely in the evening, then scattered showers after midnight. Lows 66 to 71 near the shore to around 55 at 4000 feet. North winds 10 to 15 mph shifting to the northeast after midnight. Chance of rain 60 percent.

Tuesday: Partly sunny with scattered showers. Highs 80 to 85 near the shore to around 70 at 4000 feet. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Kona

Today: Sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs around 85 near the shore to around 73 near 5000 feet. West winds up to 10 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy in the evening then becoming mostly clear. Isolated showers. Lows around 72 near the shore to 51 to 57 near 5000 feet. Light winds becoming east up to 10 mph after midnight. Chance of rain 20 percent.

Tuesday: Sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs 82 to 87 near the shore to around 73 near 5000 feet. Light winds. Chance of rain 20 percent.

Waimea

Today: Breezy. Partly sunny with scattered showers. Highs 66 to 85. East winds 10 to 20 mph. Chance of rain 50 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 63 to 69 near the shore to 55 to 62 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Tuesday: Mostly sunny in the morning then becoming partly sunny. 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 66 to 85. East winds 10 to 20 mph. Chance of rain 50 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 63 to 69 near the shore to 55 to 62 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Tuesday: Mostly sunny in the morning then becoming partly sunny. Scattered showers. Highs 65 to 84. East winds 10 to 15 mph. Chance of rain 50 percent.

South Big Island

Today: Sunny in the morning then becoming partly sunny. Breezy. Highs around 84 near the shore to around 69 near 5000 feet. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon.

Tonight: Breezy. Mostly cloudy with isolated showers in the evening, then mostly clear after midnight. Lows around 72 near the shore to around 52 near 5000 feet. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Tuesday: Sunny in the morning then becoming partly sunny. Highs around 84 near the shore to around 68 near 5000 feet. East winds 10 to 15 mph.

Puna

Today: Partly sunny with scattered showers. Highs 81 to 86 near the shore to around 71 at 4000 feet. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Showers likely in the evening, then scattered showers after midnight. Lows 66 to 71 near the shore to around 55 at 4000 feet. North winds 10 to 15 mph shifting to the northeast after midnight. Chance of rain 60 percent.

Tuesday: Partly sunny with scattered showers. Highs 80 to 85 near the shore to around 70 at 4000 feet. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Waikoloa

Today: Sunny. Highs 82 to 89 near the shore to 68 to 74 above 4000 feet. North winds up to 15 mph increasing to 10 to 15 mph in the afternoon.

Tonight: Mostly clear. Breezy. Lows around 73 near the shore to 50 to 59 above 4000 feet. East winds 10 to 20 mph.

Tuesday: Sunny. Highs 81 to 88 near the shore to 68 to 74 above 4000 feet. North winds around 10 mph.

Detailed Forecast

Synopsis

Moderate to locally breezy trade winds will focus brief showers mainly over windward and mauka areas into early Wednesday. The greatest coverage of trade showers will be during the overnight and early morning hours. Increasing moisture is expected to enhance trade showers over windward facing sections from late Wednesday through the end of the new work week. Locally strong trade winds may transport brief trade showers over to the leeward sections of some of the smaller islands starting Thursday.

Discussion

A 1036 mb surface high pressure system is located near 44N 157W, or about 1600 miles north of Honolulu. The pressure gradient south of this feature is producing moderate trade winds across the region early this morning. Loops of satellite imagery and radar reflectivity data show scattered low clouds and spotty showers moving into the windward sides of some of the islands.
The forecast guidance shows the surface high pressure system will build as it moves rapidly toward the south-southeast during the next few days. This will tighten the pressure gradient across the state from later today and tonight into mid-week. This will cause the trade winds to become locally breezy during the next day or two. In addition, expect a general drying trend with a windward and mauka shower pattern. In this regime, the greatest coverage of trade showers will likely be during the overnight and early morning hours into early Wednesday. Also, expect clouds and isolated showers to develop over some of the upslope sections of the Leeward Big Island each afternoon, followed by gradually clearing during the evening hours.
Starting late Wednesday, increasing moisture may result in greater windward and mauka shower coverage. In addition, locally strong trade winds starting Thursday may transport brief trade showers over to the leeward sections of some of the smaller islands, especially at night. The forecast models continua to show some differences in moisture availability heading into next weekend. However, based on recent trends, it appears that the surface and upper-level features that are expected to organize to the northwest of the region might allow increased moisture, and some enhancement of trade showers next weekend.

Aviation

Moderate trade winds and a typical pattern of rainfall will persist today, though some increase in winds are expected into Tuesday. Brief MVFR conditions will be confined to windward slopes of all islands, as well as over the Kona slopes of the Big Island during the afternoon and evening hours. Otherwise, VFR will prevail. No SIGMETs are in place, and none are expected through the afternoon. Conditions will be border line for AIRMET Tango due to some turbulence over and downwind of terrain today, and an AIRMET may be needed tonight or Tuesday.

Marine

Expect moderate to fresh trade winds to continue today across all Hawaiian waters. A high pressure system will build in from the north tomorrow, producing moderate to strong trade winds from Tuesday onward. Wind speeds will approach Small Craft Advisory (SCA) thresholds tonight, and we will monitor closely for the passably of a SCA issuance. Otherwise wind speeds will reach SCA thresholds for the typical windier waters around Maui and the Big Island starting on Tuesday. The coverage of SCA conditions may expand by Thursday to cover additional coastal water zones.
We will continue to see small surf along north facing shores during the next few days. Another small pulse from the north- northwest is possible later today into Tuesday followed by a slightly larger swell from the northwest late Thursday into Friday.
A series of small long-period south swells will continue to keep fun size surf along south facing shores through the week. Surf should trend down this weekend with mainly background energy by early next week. Surf heights along west facing shores will remain small through the week with a bit of south and northwest swell wrap keeping west side surf heights above flat levels.
Surf along east facing shores will remain near seasonal averages for the next several days. East facing surf heights should see an increase of size and chop along eastern exposures from Wednesday to Friday as trade wind speeds increase.

HFO Watches/Warnings/Advisories

None.

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Data Courtesy of NOAA.gov