Today: Partly sunny. Showers likely in the morning, then scattered showers in the afternoon. Highs 78 to 84 near the shore to 63 to 71 at 4000 feet. Northwest winds around 10 mph shifting to the east in the afternoon. Chance of rain 60 percent.
Tonight: Mostly cloudy with scattered showers. Lows 65 to 72 near the shore to 55 to 60 at 4000 feet. East winds around 10 mph in the evening becoming light. Chance of rain 50 percent.
Friday: Partly sunny with scattered showers. Highs 79 to 84 near the shore to 64 to 72 at 4000 feet. East winds around 10 mph. Chance of rain 50 percent.
Kona
Today: Sunny in the morning, then mostly cloudy with isolated showers in the afternoon. Highs 80 to 88 near the shore to around 71 near 5000 feet. Light winds becoming west around 10 mph in the afternoon. Chance of rain 20 percent.
Tonight: Mostly cloudy in the evening then becoming mostly clear. Isolated showers. Lows around 73 near the shore to 49 to 56 near 5000 feet. Light winds. Chance of rain 20 percent.
ARTICLE CONTINUES BELOW AD
ARTICLE CONTINUES BELOW AD
Friday: Sunny in the morning, then mostly cloudy with scattered showers in the afternoon. Highs 81 to 88 near the shore to around 71 near 5000 feet. Light winds becoming west around 10 mph in the afternoon. Chance of rain 30 percent.
Waimea
Today: Breezy. Partly sunny with scattered showers. Highs 66 to 88. East winds 10 to 20 mph. Chance of rain 50 percent.
Tonight: Mostly cloudy with scattered showers. Lows 64 to 71 near the shore to 55 to 63 near 3000 feet. East winds 10 to 15 mph shifting to the south after midnight. Chance of rain 50 percent.
Friday: Partly sunny in the morning then becoming mostly sunny. Scattered showers. Highs 67 to 88. East winds 10 to 15 mph. Chance of rain 50 percent.
Kohala
Today: Breezy. Partly sunny with scattered showers. Highs 66 to 88. East winds 10 to 20 mph. Chance of rain 50 percent.
ARTICLE CONTINUES BELOW AD
Tonight: Mostly cloudy with scattered showers. Lows 64 to 71 near the shore to 55 to 63 near 3000 feet. East winds 10 to 15 mph shifting to the south after midnight. Chance of rain 50 percent.
Friday: Partly sunny in the morning then becoming mostly sunny. Scattered showers. Highs 67 to 88. East winds 10 to 15 mph. Chance of rain 50 percent.
South Big Island
Today: Breezy. Sunny in the morning, then cloudy with isolated showers in the afternoon. Highs 81 to 87 near the shore to around 68 near 5000 feet. Northeast winds 10 to 15 mph shifting to the east 10 to 20 mph in the afternoon. Chance of rain 20 percent.
Tonight: Mostly cloudy with isolated showers in the evening, then mostly clear after midnight. Lows around 73 near the shore to around 52 near 5000 feet. Northeast winds 10 to 15 mph. Chance of rain 20 percent.
Friday: Sunny in the morning then becoming mostly cloudy. Highs 82 to 87 near the shore to around 68 near 5000 feet. East winds 10 to 15 mph.
Puna
ARTICLE CONTINUES BELOW AD
Today: Partly sunny. Showers likely in the morning, then scattered showers in the afternoon. Highs 78 to 84 near the shore to 63 to 71 at 4000 feet. Northwest winds around 10 mph shifting to the east in the afternoon. Chance of rain 60 percent.
Tonight: Mostly cloudy with scattered showers. Lows 65 to 72 near the shore to 55 to 60 at 4000 feet. East winds around 10 mph in the evening becoming light. Chance of rain 50 percent.
Friday: Partly sunny with scattered showers. Highs 79 to 84 near the shore to 64 to 72 at 4000 feet. East winds around 10 mph. Chance of rain 50 percent.
Waikoloa
Today: Mostly sunny. Isolated showers in the afternoon. Highs 79 to 90 near the shore to 67 to 74 above 4000 feet. Southeast winds 10 to 15 mph shifting to the north in the afternoon. Chance of rain 20 percent.
Tonight: Mostly clear. Isolated showers in the evening. Lows around 74 near the shore to 50 to 57 above 4000 feet. Southeast winds around 10 mph. Chance of rain 20 percent.
Friday: Sunny. Highs 81 to 90 near the shore to 67 to 75 above 4000 feet. Light winds becoming north around 10 mph in the afternoon.
Detailed Forecast
Synopsis
Light to moderate trade winds will deliver low clouds and a few showers to windward areas through Friday, while leeward areas remain mostly dry. Lighter winds on Saturday may allow a few afternoon showers to develop over leeward and interior areas. Moisture associated with a dissipating front could bring more widespread windward showers on Sunday and Monday, especially to Kauai and Oahu, with trade winds increasing slightly.
Discussion
Mostly dry trade wind weather remained in place most of the night, but a slight increase in low-level moisture associated with a weak low-level trough has brought a few showers to windward portions of Maui and the Big Island. A mid-level ridge centered NW of the islands will continue to support a relatively low and strong subsidence inversion, so this increased moisture will likely only lead to a modest increase in primarily windward showers over the next 24 hours or so. Light to moderate trade winds will prevail through Friday, supported by a surface high pressure cell centered far NE of the islands.
A cut-off deep-layer low will develop far to the NE on Friday, then move S along 150W this weekend, sending an associated front toward the islands from the N. This will substantially weaken the local pressure gradient Friday night into Saturday, with some uncertainty with the forecast thereafter. The light winds will briefly allow land and sea breezes to influence weather over land, with clouds and showers over interior areas during the afternoon, becoming mostly clear night and morning.
Reduced forecast confidence thereafter is due to somewhat inconsistent model guidance regarding the southward progression of the front on Sunday and Monday, but a consensus appears to be developing. A weakening E-W oriented band of showery low clouds is now anticipated to move S over Kauai and Oahu Sunday and Monday, with a slight increase in NE winds over Kauai, before the boundary stalls and dissipates over the islands through Tuesday. This is somewhat early in the season for a frontal boundary to make it to the latitude of the islands, so a significant air mass change is not expected. It does appear increasingly likely that a band of clouds and showers will move over Kauai and Oahu, bringing mainly windward showers, Sunday into Monday.
Aviation
High pressure far northeast of the state will maintain light to moderate trade winds through the forecast period. The relatively dry air mass will continue to limit cloud and shower activity for most areas today. Expect mainly VFR conditions, but the old front near Kauai may bring a few isolated showers this morning. Will see an increase in clouds and showers across windward areas tonight as moisture arrives from the east. Conditions will remain mainly VFR, but could see occasional MVFR conditions under passing showers.
No AIRMETs are currently in effect. However, AIRMET Sierra for mountain obscuration over windward areas may be needed tonight.
Marine
A weak high pressure ridge north of the state will continue to produce moderate to fresh trade winds into Friday morning. Wind speeds will weaken by Friday afternoon as a cold front dropping in out of the north will weaken the ridge. Expect light to moderate trade winds from Friday onward as this weakening frontal boundary slows down and then stalls out near Kauai and Oahu on Sunday. Moderate to locally fresh trade winds move into the region just north of the front, these stronger trades will spread across the region by Tuesday as the frontal boundary fades away.
A series of small north and northwest swells are expected along north facing exposures through Friday. Forerunners from a slightly larger north-northwest swell will fill in Friday and peak over the weekend. A cut off low will develop far north of the state on today through Friday, sending a north swell towards the islands arriving by Sunday. A decent fetch area will point towards Hawaii with 20 to 35 knots of wind developing around the west side of the low center. Depending on how the storm develops over the next 48 hours, we could see surf heights approaching High Surf Advisory thresholds along north facing shores on Monday.
Surf will remain small along south facing shores over the next few days with mainly background energy from the south and southeast. Another small, a more noticeable long-period south swell is expected to fill in Sunday into Monday then decline through the middle of next week.
East facing shores will remain small during the next several days due to the lack of strong trade winds upstream of the state. Areas exposed to the north should see an increase Sunday into Monday as a moderate north-northeast swell wraps into select eastern exposures.
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