West Side

Today: Breezy. Mostly cloudy with scattered showers. Highs 80 to 85. Northeast winds 10 to 20 mph. Chance of rain 40 percent.

Tonight: Mostly cloudy. Breezy. Isolated showers in the evening, then scattered showers after midnight. Lows 69 to 76. Northeast winds 15 to 20 mph. Chance of rain 50 percent.

Saturday: Breezy. Mostly sunny with isolated showers. Highs 80 to 86. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

South Side

Today: Breezy. Mostly cloudy with isolated showers. Highs around 88. Northeast winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 20 percent.

Tonight: Mostly cloudy. Isolated showers after midnight. Lows 69 to 77. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Saturday: Mostly sunny. Breezy. Isolated showers in the morning. Highs around 89. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

North Shore

Today: Mostly cloudy. Breezy. Showers likely in the morning, then scattered showers in the afternoon. Highs around 83 near the shore to around 66 near 5000 feet. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 70 percent.

Tonight: Mostly cloudy. Showers likely in the evening, then occasional showers after midnight. Lows around 72 near the shore to around 53 near 5000 feet. East winds 10 to 15 mph. Chance of rain 90 percent.

Saturday: Mostly cloudy. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs around 83 near the shore to around 66 near 5000 feet. East winds 10 to 20 mph. Chance of rain 70 percent.

Central Maui

Today: Mostly cloudy. Breezy. Scattered showers in the morning, then isolated showers in the afternoon. Highs 82 to 89. Northeast winds 10 to 25 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy. Breezy. Isolated showers in the evening, then scattered showers after midnight. Lows around 72. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Saturday: Breezy. Mostly sunny with isolated showers. Highs 82 to 89. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Upcountry

Today: Mostly cloudy. Windy. Scattered showers in the morning, then isolated showers in the afternoon. Highs around 62 at the visitor center to around 68 at the summit. East winds up to 30 mph. Chance of rain 50 percent.

Tonight: Windy. Mostly cloudy with scattered showers. Lows around 49 at the visitor center to around 46 at the summit. East winds 10 to 30 mph. Chance of rain 50 percent.

Saturday: Partly sunny in the morning then becoming mostly sunny. Breezy. Scattered showers. Highs around 62 at the visitor center to around 68 at the summit. East winds up to 25 mph. Chance of rain 50 percent.

East Maui

Today: Mostly cloudy. Breezy. Showers likely in the morning, then scattered showers in the afternoon. Highs around 83 near the shore to around 66 near 5000 feet. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 70 percent.

Tonight: Mostly cloudy. Showers likely in the evening, then occasional showers after midnight. Lows around 72 near the shore to around 53 near 5000 feet. East winds 10 to 15 mph. Chance of rain 90 percent.

Saturday: Mostly cloudy. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs around 83 near the shore to around 66 near 5000 feet. East winds 10 to 20 mph. Chance of rain 70 percent.

Lanai City

Today: Breezy. Mostly cloudy with scattered showers. Highs 74 to 82. Northeast winds 10 to 20 mph. Chance of rain 40 percent.

Tonight: Breezy. Partly cloudy in the evening, then mostly cloudy with isolated showers after midnight. Lows around 67. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Saturday: Mostly sunny with isolated showers. Highs 74 to 82. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Kaunakakai

Today: Breezy. Cloudy with scattered showers in the morning, then partly sunny with isolated showers in the afternoon. Highs 73 to 88. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Tonight: Breezy. Partly cloudy with isolated showers. Lows 60 to 75. Northeast winds 15 to 20 mph. Chance of rain 20 percent.

Saturday: Mostly sunny. Breezy. Isolated showers in the morning. Highs 73 to 89. Northeast winds 15 to 20 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

An upper level low pressure system, currently situated a few hundred miles west of Kauai, will slowly drift to the west southwest for the next several days. Moderate to locally strong trade winds, coupled with moisture and instability associated with the low, will continue to bring enhanced showers and isolated thunderstorms to much of the state through at least Saturday. Another upper level low is forecast to drop southward towards the islands early next week and maintain an unsettled weather pattern.

Discussion

Radar continues to indicate enhanced shower activity over mainly northeast and eastern portions of all islands and adjacent coastal waters. Overnight rainfall accumulation totals, however, have not been overly impressive with less than an inch recorded for the wettest standout locations. Unstable conditions aloft, as noted on the 12Z Lihue RAOB sounding, along with low level convergent boundaries, have aided in the development of thunderstorms just south of Oahu and north of Kauai early this morning. A Flood Watch has been issued for Kauai through noon to account for a cluster of thunderstorms north of Kauai slowly sagging to the southward. This Watch may need to be extended in time depending on the evolution of complex later today.
An upper level low, centered roughly 200 miles west of Kauai, has been responsible for the unsettled weather experienced over the past 24 hours. Both the GFS and ECMWF prog the low to drift slowly westward through Saturday. Thus, with the associated instability still in place, moderate to locally strong trades will continue to drive rounds of enhanced showers and isolated thunderstorms over the state through early this weekend. Most heavy rain and thunderstorm activity remain over Oahu, Kauai, and their surrounding coastal waters, closest to the aforementioned low. Shower activity may wane slightly Saturday morning into Sunday as the upper level feature moves further west, away from the state.
The first upper low will be replaced by a second one late Monday. This next one will stall to the northeast of the state and weaken through mid week. However, an upper trough connecting the remnants of the first low to our SW and the second one to the NE will remain over the area. This feature should help to maintain enhanced showers in a moderate to breezy trade wind pattern.

Aviation

An upper level low pressure system just west of the state will continue to bring an unstable airmass with enhanced showers to the entire area today. However, these showers will be mainly focused along northeast and east portions of the islands. There will isolated thunderstorms across the affect airports on Kauai and Oahu along with areas over their adjacent coastal waters. Expect periods MVFR conditions, along with isolated IFR ceilings and visibility in some of the more robust showers and storms.
AIRMET SIERRA remains in effect for Big Island, Oahu, Kauai, Molokai, and Maui above 2000 feet for tempo mountain obscuration due to clouds and showers. SIERRA will likely continue through the remainder of the day.
AIRMET TANGO is in effect for across the island chain for tempo moderate turbulence between FL300 and FL350. This is expected to through the remainder of the day.

Marine

Moderate to locally strong trades will remain in place over the Hawaiian coastal waters through Saturday. Trade winds will weaken hold in the fresh to moderate range through early next week. An upper low north of Kauai continues to drifting southwestward into the northern coastal waters today and will keep isolated thunderstorms in the forecast over the waters into the weekend. A Small Craft Advisory (SCA) remains in effect for windier waters and channels surrounding Maui and the Big Island. The SCA was expanded to include northern coastal waters near Kauai and Oahu.
Two moderate, long period NW and NNW swells moving through the Hawaii region will keep surf heights elevated along N and W facing shores through the end of the week. Surf along N and W facing shores slowly trends down on Sunday. A hurricane force low E of Japan will bring another round of moderate, long period NW (330 deg) swell into the islands building surf heights along N and W facing shores from next Wednesday onward. This next long period swell may possibly reach low end High Surf Advisory levels from Wednesday into Thursday if we add a one to two foot upward adjustment to swell heights as compared to the ECMWF Wave model.
A series of small, medium to long period S to SW swells filter into the area into the weekend, keeping S shores from going flat. Short period surf along E shores picks up through the weekend as trade winds strengthen.

Fire weather

Wind speeds and afternoon minimum humidity levels will remain below critical fire weather thresholds through the forecast period. Locally heavy rain and thunderstorms are possible through early Saturday. Unstable conditions will continue to produce wet weather across the state through early next week. Temperature inversion heights near Maui and the Big Island will range from the 7,000 to 8,000 feet MSL today.

HFO Watches/Warnings/Advisories

Flood Watch until noon HST today for Niihau, Kauai,
Small Craft Advisory until 6 PM HST this evening for Kauai Northwest Waters, Kauai Windward Waters, Kauai Channel, Oahu Windward Waters.
Small Craft Advisory until 6 PM HST Saturday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

Data Courtesy of NOAA.gov