Photo Credit: Tyler Rooke

West Side

Today: Partly sunny with a 20 percent chance of showers in the morning, then mostly sunny in the afternoon. Highs 76 to 82. Northeast winds up to 15 mph.

Tonight: Mostly clear. Lows 64 to 71. East winds up to 10 mph.

Sunday: Sunny. A 20 percent chance of showers in the afternoon. Highs 76 to 82. Light winds.

South Side

Today: Partly sunny in the morning then becoming mostly sunny. Highs around 84. North winds up to 10 mph.

Tonight: Mostly clear. Lows 63 to 72. North winds up to 10 mph.

Sunday: Sunny. Highs around 85. Light winds.

North Shore

Today: Partly sunny. Chance of showers in the morning, then slight chance of showers in the afternoon. Highs 76 to 81 near the shore to around 64 near 5000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Partly cloudy with a 20 percent chance of showers. Lows around 68 near the shore to around 49 near 5000 feet. Southeast winds up to 10 mph.

Sunday: Sunny. A 20 percent chance of showers in the morning. Highs 76 to 81 near the shore to around 65 near 5000 feet. East winds up to 10 mph.

Central Maui

Today: Partly sunny in the morning then becoming mostly sunny. Highs 79 to 85. Northeast winds up to 15 mph.

Tonight: Mostly clear. Lows 63 to 68. Northeast winds up to 10 mph in the evening becoming light.

Sunday: Sunny. Highs 80 to 86. Light winds.

Upcountry

Today: Partly sunny. A 50 percent chance of showers in the morning. Highs around 60 at the visitor center to around 62 at the summit. East winds up to 10 mph in the morning becoming light.

Tonight: Mostly clear. Lows around 44 at the visitor center to around 49 at the summit. Light winds.

Sunday: Sunny. A 20 percent chance of showers in the afternoon. Highs around 62 at the visitor center to around 70 at the summit. Light winds.

East Maui

Today: Partly sunny. Chance of showers in the morning, then slight chance of showers in the afternoon. Highs 76 to 81 near the shore to around 64 near 5000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Partly cloudy with a 20 percent chance of showers. Lows around 68 near the shore to around 49 near 5000 feet. Southeast winds up to 10 mph.

Sunday: Sunny. A 20 percent chance of showers in the morning. Highs 76 to 81 near the shore to around 65 near 5000 feet. East winds up to 10 mph.

Lanai City

Today: Partly sunny in the morning then becoming mostly sunny. Highs 70 to 78. Northeast winds up to 15 mph.

Tonight: Mostly clear. Lows around 62. Northeast winds up to 10 mph.

Sunday: Sunny. A 20 percent chance of showers in the afternoon. Highs 70 to 79. Light winds.

Kaunakakai

Today: Partly sunny in the morning then becoming mostly sunny. Highs 66 to 85. East winds up to 10 mph.

Tonight: Mostly clear. Lows 55 to 71. East winds up to 10 mph.

Sunday: Sunny. Highs 67 to 86. Light winds.

Detailed Forecast

Synopsis

Trade winds will weaken today, becoming light and variable winds from Sunday into the first half next week. Weather conditions in this light wind pattern will remain fairly stable with passing low clouds and light showers especially during the afternoon. Rain chances increase from Thursday into Friday as a weak cold front moves into and stalls out over the islands.

Discussion

High level cirrus clouds are streaming in from west to east across the island chain due to a subtropical jet stream in the upper atmosphere. The low level clouds look fairly stable in this morning satellite imagery and stable conditions aloft will tend to limit shower activity favoring island mountains and interior sections each afternoon through the weekend. Upper air weather balloon soundings from Lihue, Kauai and Hilo, Hawaii show subsidence temperature inversion heights around the 6,000 feet elevation level. These stable temperature inversion heights will tend to limit cloud growth and generally produce brief periods of isolated to scattered shower activity.
The subtropical ridge axis currently over the islands keeping fairly stable conditions in the forecast will drift south of the state from Sunday onward. Expect a slight increase in shower trends during the first half of next week in a light wind afternoon onshore sea breeze weather regime. Clouds and a few showers will develop by late morning to afternoon over island mountain and interior sections through Wednesday. Rainfall amounts will be light due to the large scale atmospheric stability.
By Thursday, long range model guidance continues to show a shallow cold front creeping into the western islands from the northwest direction. Widespread showers and breezy trade winds will develop along the weakening frontal band as it passes through each island, stalling out near Maui by Friday morning. All islands will benefit from a period of enhanced showers along the frontal band, especially along the windward and mountain slopes of each island. The frontal band will then break apart by Friday afternoon, with remnant unstable cloud bands drifting into each island on the strengthening easterly trade winds.

Aviation

Light to moderate trades weaken through the weekend, allowing for localized land/sea breeze development. Another band of moisture riding the trades should move in overnight increasing SHRA and low cigs mostly along windward and mauka locations. MVFR conds can be expected in any SHRA but otherwise VFR should prevail.
AIRMET Tango is in effect for mod turb between FL250 and FL450 across the state.
SIGMET Papa for severe upper level turb is in effect for an area just west of the main Hawaiian Islands this evening. This area of severe turb is expected to move over the islands late tonight into Saturday morning.

Marine

A front approaching from the northwest will stall and weaken northwest of the coastal waters this weekend. Light background flow will shift to southeasterlies by Sunday. Another front will approach from the northwest early next week will keep gentle south to southeast winds in place.
An extra-large northwest (310-320) swell peaked overnight and is starting to decline. However, this swell will continue to generate surf heights in excess of warning threshold along affected north and west facing shorelines through today. A High Surf Warning (HSW) remains in effect through 6pm HST this evening for most north and west-facing shores of the smaller islands and for west facing shores of the Big Island. Expect periodic overtopping of vulnerable coastal roadways and wave runup to coastal properties. A gradual downward trend will continue through this weekend and surf should decrease below advisory threshold during the day Sunday. In addition, a Small Craft Advisory (SCA) remains in effect for most coastal waters for seas greater than 10 ft. This SCA is expected to hold through today.
Looking ahead into next week, a stretch of elevated north and west shore surf is expected, produced by overlapping northwest pulses ranging from large to potentially extra-large, particularly from Wednesday onward. Surf along east facing shores will remain slightly elevated through the weekend due to the lingering short- period north- northeast swell. Early next week, east facing shore surf will remain small. Surf along south facing shores will see an uptick heading into next week from a series of consecutive southwest pulses. This will result in small to moderate surf, peaking Monday and Tuesday.

Fire weather

Critical fire weather conditions are not expected through early next week as winds remain below warning thresholds. Daytime relative humidity may briefly touch critical levels over drier leeward zones into next week.

HFO Watches/Warnings/Advisories

High Surf Warning until 6 PM HST this evening for Niihau, Kauai Leeward, Waianae Coast, Oahu North Shore, Maui Windward West, Kona, Kohala, Kauai North, Koolau Windward, Molokai Windward, Molokai North, Molokai West, Windward Haleakala.
Small Craft Advisory until 6 PM HST this evening for all Hawaiian waters except Maalaea Bay,

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Data Courtesy of NOAA.gov