Photo Credit: James Grenz

Hilo

Today: Mostly cloudy. Showers likely in the morning, then scattered showers in the afternoon. Highs around 79 near the shore to 64 to 69 at 4000 feet. North winds up to 15 mph shifting to the northeast in the afternoon. Chance of rain 70 percent.

Tonight: Mostly cloudy. Scattered showers early in the evening, then occasional showers in the late evening and overnight. Lows around 65 near the shore to around 51 at 4000 feet. Light winds. Chance of rain 80 percent.

Saturday: Mostly cloudy with showers likely. Highs around 80 near the shore to 65 to 70 at 4000 feet. Light winds. Chance of rain 70 percent.

Kona

Today: Mostly sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs 79 to 84 near the shore to around 70 near 5000 feet. Northwest winds up to 10 mph shifting to the west in the afternoon. Chance of rain 40 percent.

Tonight: Partly cloudy. Scattered showers early in the evening, then isolated showers in the late evening and overnight. Lows 65 to 70 near the shore to around 52 near 5000 feet. Light winds. Chance of rain 40 percent.

Saturday: Mostly sunny in the morning, then partly sunny with scattered showers in the afternoon. Highs 80 to 85 near the shore to around 71 near 5000 feet. Light winds. Chance of rain 40 percent.

Waimea

Today: Partly sunny with scattered showers. Highs around 78 near the shore to 70 to 77 near 3000 feet. Northeast winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows around 64 near the shore to 50 to 58 near 3000 feet. East winds around 10 mph. Chance of rain 50 percent.

Saturday: Partly sunny with scattered showers. Highs 64 to 80. Light winds. Chance of rain 50 percent.

Kohala

Today: Partly sunny with scattered showers. Highs around 78 near the shore to 70 to 77 near 3000 feet. Northeast winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows around 64 near the shore to 50 to 58 near 3000 feet. East winds around 10 mph. Chance of rain 50 percent.

Saturday: Partly sunny with scattered showers. Highs 64 to 80. Light winds. Chance of rain 50 percent.

South Big Island

Today: Mostly sunny. Isolated showers in the afternoon. Highs around 82 near the shore to around 71 near 5000 feet. Southwest winds up to 10 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Isolated showers early in the evening. Lows around 67 near the shore to around 51 near 5000 feet. Northeast winds around 10 mph in the evening becoming light. Chance of rain 20 percent.

Saturday: Mostly sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs around 83 near the shore to around 72 near 5000 feet. Light winds. Chance of rain 20 percent.

Puna

Today: Mostly cloudy. Showers likely in the morning, then scattered showers in the afternoon. Highs around 79 near the shore to 64 to 69 at 4000 feet. North winds up to 15 mph shifting to the northeast in the afternoon. Chance of rain 70 percent.

Tonight: Mostly cloudy. Scattered showers early in the evening, then occasional showers in the late evening and overnight. Lows around 65 near the shore to around 51 at 4000 feet. Light winds. Chance of rain 80 percent.

Saturday: Mostly cloudy with showers likely. Highs around 80 near the shore to 65 to 70 at 4000 feet. Light winds. Chance of rain 70 percent.

Waikoloa

Today: Mostly sunny. Isolated showers in the afternoon. Highs around 81 near the shore to 65 to 72 above 4000 feet. East winds up to 15 mph shifting to the north in the afternoon. Chance of rain 20 percent.

Tonight: Partly cloudy. Isolated showers early in the evening. Lows around 69 near the shore to 47 to 55 above 4000 feet. Light winds. Chance of rain 20 percent.

Saturday: Mostly sunny. Isolated showers in the afternoon. Highs around 82 near the shore to 66 to 73 above 4000 feet. Light winds. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Light to moderate trade winds will continue today, along with clouds and showers favoring the windward and mauka areas. Increased shower activity will continue over the Big Island overnight due to a nearby upper level feature. Winds will shift out of the north-northeast over the weekend, with the best rainfall chances remaining over and around the Big Island.

Discussion

Some minor changes to the forecast with the morning package, although the forecast philosophy remains the same. Have boosted PoPs in several areas to nudge to higher numbers based on the latest blend of models and high resolution models. Have also boosted QPF for the first 36 hours or so to reflect the higher amounts anticipated versus typical trade wind showers.
The trailing end of a surface trough remains near the Big Island and Maui this morning, and an upper level trough remains over the islands. The forecast does not include thunderstorms today near the Big Island, as there is good model agreement with the instability axis moving just far enough to the east. The surface trough is expected to move to the east and weaken over the next couple of days, while the upper level feature lingers.
Expect moderate trade winds to continue today, particularly for Kauai and Oahu. Slightly lighter trades are expected for Maui County and the Big Island due to their proximity to the surface trough. Clouds and showers will favor the windward and mauka areas of the islands, however with the upper level trough, there is little in the way of a trade wind inversion, so showers may bring some higher rainfall totals than normal trade wind showers.
Most of the instability with the upper level feature will remain to the east of the islands. However the southern end of the feature will be close enough to the Big Island which could initiate some more shower activity there over the next couple of days versus the other islands.
Behind the surface trough, a new ridge will push in over the weekend and early next week. This will likely turn the winds a bit more northerly, so expect more north-northeast trade wind flow. For Oahu and Kauai, as the ridge builds in, expect a trade wind inversion to set up, which will help to limit rainfall totals. Limited moisture moving in will also limit shower activity. The upper trough lingering over the eastern end of the state will likely mean lingering shower activity.

Aviation

Current satellite trends show the areal extent of the dense upper lvl cloud deck, which has been in place across the eastern portions of the state, slowly beginning to erode as the upper trough moves slightly eastward. Otherwise, east to northeast trades will concentrate a majority of clouds and showers across windward areas of the islands through the TAF period. The best chance for persistent showers, along with any MVRF or possible IFR conditions, remains over the eastern portions of the state stretching from Maui to the Big Island, in response to the lingering plume of deeper layer moisture in that region.
AIRMET Tango for moderate upper turb between FL220 and FL360 remains in effect from Molokai to the Big Island. Turbulent conditions are expected to continue in this region into this afternoon.
AIRMET Sierra for MTN TEMPO OBSC abv 025kft due to CLD and SHRA, continues for the north through southeast sections of the Big Island. These conditions are expected to continue into this afternoon, and possibly need to be expanded to include other windward locations later this morning.

Marine

A surface trough lingers near the Big Island and Maui this morning with an upper level disturbance producing scattered thunderstorms east of the trough axis over the eastern offshore waters. Strong winds in the far eastern waters are decreasing this morning. Expect elevated seas over the Big Island windward waters this morning and a Small Craft Advisory (SCA) was extended through this evening for 10 foot significant wave heights. These elevated seas will likely decrease below SCA thresholds later this afternoon. Elsewhere, light to moderate easterly trade winds continue as the surface trough lingers over the islands through the weekend. Expect continued periods of unsettled weather in the coastal and offshore waters for the next few days.
The current west-northwest swell continues to slowly decrease today. A pair of moderate northwest swells are expected to move into the region from tonight through the weekend. The first swell will begin to arrive near Kauai by early evening and will spread eastward across the state. A second slightly larger northwest swell will arrive on Saturday, briefly approaching High Surf Advisory levels along north and west facing shores of Niihau, Kauai, Oahu and Molokai. This northwest swell decreases on Sunday, as a small north swell with a wave period of around 10 seconds arrives, which may produce a slight boost in surf heights along north facing shores by early next week.
Surf heights along select east facing shores of the Big Island remain elevated and will slowly decrease today as upstream winds over the eastern off-shore waters decrease. Surf heights along east facing shores of all islands will hold at moderate levels through the weekend. Surf along south facing shores has returned to background levels and will remain small through next week.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 PM HST this evening for Big Island Windward Waters.

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Data Courtesy of NOAA.gov