Photo Credit: Jason Weingardt

West Kaua’i

Today: Mostly sunny with a 20 percent chance of showers. Highs around 84 near the shore to around 73 above 3000 feet. Light winds.

Tonight: Mostly clear. Lows around 67 near the shore to around 57 above 3000 feet. Light winds.

Sunday: Mostly sunny. A 20 percent chance of showers in the afternoon. Highs 82 to 87 near the shore to around 73 above 3000 feet. East winds up to 10 mph shifting to the south in the afternoon.

South Kaua’i

Today: Mostly sunny. Chance of showers in the morning, then slight chance of showers in the afternoon. Highs 77 to 85. Northeast winds around 10 mph. Chance of rain 30 percent.

Tonight: Mostly clear. Lows around 69. Northeast winds up to 10 mph.

Sunday: Sunny. Highs 78 to 85. Light winds.

Kaua’i Mountains

Today: Mostly sunny with a 40 percent chance of showers. Highs 70 to 80 in the valleys to around 63 above 4000 feet. Light winds.

Tonight: Partly cloudy. A 20 percent chance of showers in the evening. Lows 59 to 66 in the valleys to around 55 above 4000 feet. Light winds.

Sunday: Mostly sunny with a 20 percent chance of showers. Highs 72 to 81 in the valleys to around 64 above 4000 feet. Light winds.

North Kaua’i

Today: Mostly sunny with a 20 percent chance of showers. Highs 73 to 84. Southeast winds up to 10 mph shifting to the northeast in the afternoon.

Tonight: Mostly clear. Lows 61 to 69. Light winds.

Sunday: Mostly sunny. A 20 percent chance of showers in the afternoon. Highs 74 to 84. Light winds.

East Kaua’i

Today: Mostly sunny. Chance of showers in the morning, then slight chance of showers in the afternoon. Highs 70 to 83. Northeast winds up to 10 mph. Chance of rain 40 percent.

Tonight: Mostly clear. A 20 percent chance of showers after midnight. Lows 61 to 72. Light winds.

Sunday: Mostly sunny with a 20 percent chance of showers. Highs 71 to 83. 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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