Hilo

Today: Partly sunny with scattered showers. Highs around 81 near the shore to 66 to 71 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows around 66 near the shore to around 52 at 4000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Saturday: Partly sunny with scattered showers. Highs around 81 near the shore to 66 to 71 at 4000 feet. East winds up to 10 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 50 percent.

Kona

Today: Sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs around 83 near the shore to 65 to 70 near 5000 feet. Light winds. Chance of rain 20 percent.

Tonight: Partly cloudy. Lows 69 to 74 near the shore to around 55 near 5000 feet. Light winds.

Saturday: Sunny in the morning, then partly sunny with isolated showers in the afternoon. Highs around 83 near the shore to around 69 near 5000 feet. Light winds becoming west up to 10 mph in the afternoon. Chance of rain 20 percent.

Waimea

Today: Mostly sunny in the morning then becoming partly sunny. Breezy. Scattered showers. Highs around 80 near the shore to 70 to 76 near 3000 feet. East winds up to 15 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 40 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows around 65 near the shore to 50 to 63 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Saturday: Partly sunny in the morning then becoming mostly sunny. Breezy. Scattered showers. Highs around 80 near the shore to 70 to 76 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Kohala

Today: Mostly sunny in the morning then becoming partly sunny. Breezy. Scattered showers. Highs around 80 near the shore to 70 to 76 near 3000 feet. East winds up to 15 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 40 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows around 65 near the shore to 50 to 63 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

Saturday: Partly sunny in the morning then becoming mostly sunny. Breezy. Scattered showers. Highs around 80 near the shore to 70 to 76 near 3000 feet. East winds 10 to 20 mph. Chance of rain 50 percent.

South Big Island

Today: Mostly sunny. Breezy. Isolated showers in the afternoon. Highs around 82 near the shore to around 68 near 5000 feet. East winds up to 20 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Breezy. Lows around 71 near the shore to around 54 near 5000 feet. Northeast winds 10 to 25 mph.

Saturday: Mostly sunny. Breezy. Isolated showers in the afternoon. Highs around 82 near the shore to around 68 near 5000 feet. Northeast winds up to 25 mph shifting to the east 10 to 20 mph in the afternoon. Chance of rain 20 percent.

Puna

Today: Partly sunny with scattered showers. Highs around 81 near the shore to 66 to 71 at 4000 feet. Northeast winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows around 66 near the shore to around 52 at 4000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Saturday: Partly sunny with scattered showers. Highs around 81 near the shore to 66 to 71 at 4000 feet. East winds up to 10 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 50 percent.

Waikoloa

Today: Sunny. Highs around 84 near the shore to 55 to 72 above 4000 feet. North winds up to 15 mph.

Tonight: Mostly clear. Lows 67 to 74 near the shore to 49 to 59 above 4000 feet. East winds up to 15 mph.

Saturday: Mostly sunny. Highs around 84 near the shore to 65 to 72 above 4000 feet. Northwest winds up to 10 mph.

Detailed Forecast

Synopsis

Mostly dry trade wind weather will persist through early Saturday. The winds will weaken and veer southeasterly starting Saturday night as a front approaches the state from the northwest. The front is expected to reach the western end of the island chain late Monday, before it stalls on Tuesday. Moisture along this front may bring periods of rainfall to windward and north facing slopes. Some showers will also be possible over leeward areas of the western islands. Expect breezy trade winds from Tuesday through the middle of next week.

Discussion

A 1027 mb surface high pressure system is centered near 38N 159W, or slightly more than 1100 miles north of Honolulu. The tightening pressure gradient south of this feature is producing locally breezy trade winds across most of the island chain early this morning.
Loops of water vapor imagery show an upper-level low centered about 275 miles southwest of Lihue. This feature seems to be having minimal impact on the local weather, since the atmosphere is rather dry across the region. In addition, stable conditions prevail due to a mid-level ridge dominating the atmosphere directly above the islands. The result is that most of the state is experiencing a dry trade wind weather pattern. Satellite imagery shows an area of cirrus clouds mainly over the eastern end of the state. There are also some low clouds with a few light showers along windward facing slopes and coasts, while leeward sections of the smaller islands have mostly clear skies.
The forecast guidance shows the surface high far north of the state moving toward the east-southeast this morning, and then toward the east from this afternoon into this weekend. The stable mid-level ridge and dry atmosphere conditions will also continue. Therefore, expect the dry trade wind weather pattern to persist through early Saturday. There may be a few brief showers over some windward and mauka sections. Some showers are also possible along the upslope sections of the leeward Big Island each afternoon, but most leeward areas of the smaller island should remain rather dry.
Both the GFS and ECMWF models show a cold front approaching the islands by Sunday. At the same time, the surface high will have moved far east-northeast of the state. This will cause the low- level flow to weaken and shift out of the southeast late Saturday through Sunday. These winds may bring some slight increase in moisture to the islands ahead of the front, but there does not appear to be a significant surge of moisture out of the tropical regions to our south. The front still appears to reach Kauai by late Monday, but the forecast models differ on how far this front will eventually push down across the rest of the island chain. The GFS model brings it down near the central islands Tuesday, while the ECMWF model appears to show it stalling just west of Oahu. For now, we are indicating there will be increased clouds and rainfall over the western end of the island chain early next week, especially over windward and north facing sections of Kauai and Oahu. Then depending on how strong the front is, and how far down the island chain it pushes, there may be increased rainfall over portions of Maui County. The models also suggest some rainfall may occur over leeward sections of Kauai, and possibly Oahu.
The output from both of the global models show breezy trade winds developing over the state as the front stalls. These breezy trades may also be relatively wet, especially if significant moisture associated with the front is available. This breezy, and potentially wet, trade wind weather pattern will likely persist from Tuesday through the middle of next week based on the latest guidance.

Aviation

Radar trends continue to show a few light showers drifting across mainly the central and eastern islands this morning, while satellite data shows an area of low/mid clouds spreading westward across the islands. The 12z sounding data continued to show shallow inversion heights at both PHTO and PHLI, with limited low level moisture at both locations hindering the chances for shower development early this morning. Otherwise, moderate to breezy easterly trade winds will continue across the islands through tonight as a ridge of high pressure remains centered north of the state. The weaker wind pattern across leeward Big Island will continue diurnal circulations, with sea breeze clouds and showers expected later this afternoon. VFR conditions are expected at most locations throughout the forecast period, however MVFR cigs are expected within showers.
AIRMET Tango for low level mechanical turbulence downstream of higher terrain continues across all islands through today. Additionally, AIRMET Sierra for tempo mountain obscuration, may become necessary across windward sections of the islands later this morning or afternoon in persistent trade wind flow.

Marine

Moderate to locally breezy trade winds will continue as a ridge of high pressure moves farther north of the state. The Small Craft Advisory for the typically windy zones around Maui County and the Big Island is in effect through Friday night, but may need to be extended through Saturday. Winds are then forecast to weaken and veer southeast through the rest of the weekend as a front approaches from the northwest. The front will likely move through the state beginning Monday, with moderate northwest and north winds filling in behind it. The winds will quickly increase to fresh to locally strong and become northeast Monday night as the front advances farther down the island chain.
Surf along north and west facing shores will remain elevated, but below advisory levels, through Saturday as a series of small northwest swells move through the coastal waters. A larger northwest swell will fill in Sunday night into Monday, with surf likely reaching advisory levels Tuesday and Wednesday, then slowly subsiding through the rest of the week. As this swell moves down the island chain the direction will become more northerly, most likely sometime Tuesday.
East facing shores will have small, choppy surf through Friday, then slowly trend down through the weekend. Rough surf will return along east shores early next week due to the combination of north-northwest swell wrap and increasing northeasterly wind swell. Surf along south facing shores will remain small into early next week. A small south swell is possible towards the middle of next week.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 AM HST Saturday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

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Data Courtesy of NOAA.gov