West Kaua’i

Today: Sunny and breezy. Highs 85 to 91 near the shore to around 77 above 3000 feet. Northeast winds up to 20 mph.

Tonight: Partly cloudy with isolated showers. Lows 70 to 75 near the shore to around 62 above 3000 feet. Northeast winds up to 15 mph. Chance of rain 20 percent.

Friday: Mostly sunny. Isolated showers in the morning. Highs 85 to 90 near the shore to around 77 above 3000 feet. East winds up to 15 mph. Chance of rain 20 percent.

South Kaua’i

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

Tonight: Mostly cloudy with scattered showers. Lows around 74. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Friday: Breezy. Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 81 to 89. Northeast winds 10 to 20 mph. Chance of rain 40 percent.

Kaua’i Mountains

Today: Partly sunny with scattered showers. Highs 75 to 84 in the valleys to around 67 above 4000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 64 to 70 in the valleys to around 60 above 4000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Friday: Partly sunny in the morning then becoming mostly sunny. Scattered showers. Highs 74 to 84 in the valleys to around 66 above 4000 feet. East winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 50 percent.

North Kaua’i

Today: Mostly sunny with scattered showers. Highs 78 to 88. East winds up to 15 mph. Chance of rain 30 percent.

Tonight: Mostly cloudy with scattered showers. Lows 65 to 74. Southeast winds up to 10 mph. Chance of rain 50 percent.

Friday: Partly sunny in the morning then becoming mostly sunny. Scattered showers. Highs 77 to 88. East winds up to 15 mph. Chance of rain 50 percent.

East Kaua’i

Today: Partly sunny in the morning then becoming mostly sunny. Scattered showers. Highs 75 to 86. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers. Lows 65 to 77. Northeast winds up to 10 mph. Chance of rain 50 percent.

Friday: Partly sunny with scattered showers in the morning, then mostly sunny with isolated showers in the afternoon. Highs 74 to 86. Northeast winds 10 to 15 mph. Chance of rain 50 percent.

Detailed Forecast

Synopsis

Light to moderate trades prevail across the Hawaiian Islands will produce isolated to scattered showers along windward and mauka areas through Halloween Night. By the weekend, a frontal boundary will propagate southward into the western islands, bringing wetter and cloudier conditions through much of next week.

Discussion

Light to moderate trades prevail across the Hawaiian Islands as upper-level ridges continue to claim dominance well north of the state, meandering eastward over the next couple days. This will help maintain more stability over the state, limiting shower activity, with exception to the periodic isolated showers across typical windward and mauka areas.
Those participating in Trick-or-Treating can expect much of the same on Halloween Night. Light trades persist and may result in funneling showers across windward and mauka areas throughout the island chain, especially for Big Island and Maui. Skies will be mostly clear along leeward and interior aspects of all islands with a fine gradient into partly to mostly cloudy across windward exposures, in association with trade showers. Otherwise, anticipate a spooky, yet pleasant night with overnight temperatures in the low- to mid-70s for most locations across the state.
Trades will gradually weaken during the latter half of the weekend with the introduction of a frontal boundary passing from northwest to southeast across the state. However, latest model guidance hasn't been in the best of agreement with regards to timing and position of the front — the ECWMF stalls the front over Kauai early while the GFS propagates it further south into the island chain before diminishing. Given the uncertainties, confidence in the evolution of the frontal boundary, including timing and strength, still remains relatively low. Regardless, shower activity is expected to greatly increase across much of the state with the incoming frontal boundary, especially in comparison to the latter end of the week. Much like previous shifts, opted to trend wetter to account for the possibility of the aforementioned frontal boundary and elected to forgo any mention of isolated thunderstorms at this time due to the inconsistencies within the alloted model guidance.
In the long-range, additional uncertainty is portrayed by the GFS, depicting a weak, cutoff developing in the vicinity of the island chain midweek next week. Should this feature become fruitful, it would result in an increase of shower activity throughout much of next week, escorting more moisture out of the tropics. However, acknowledging this event is still several days out, it is simply worth noting so it can be monitored going forward as new guidance becomes available.

Aviation

Light to moderate trades persist through the next few days resulting in isolated shower activity along windward and mauka areas across the Hawaiian Islands. Brief periods of MVFR conditions are possible within moderate intensity showers. Otherwise, VFR conditions prevail.
AIRMET Tango is currently in effect over and around Kauai and Oahu from FL220 to FL360.

Marine

Surface high pressure anchored far northeast of the Hawaiian Islands will maintain moderate to locally strong trades into early this weekend. A Small Craft Advisory (SCA) has been issued for the Alenuihaha Channel, Maalaea Bay, and Pailolo Channel to account for some of these locally stronger winds through this afternoon. A cold front is forecast to press southward over the western waters Sunday into Monday and bring an increase in northeast winds to near SCA criteria. Weak east northeast trades will return thereafter.
A small, long period NNW swell (330) will fill in tonight and and keep surf along N and W shores elevated through Friday. Surf will then trend sharply upward late Friday through Monday in response to a couple of swells sent toward the islands by an active pattern across the N Pac. Forerunners from a moderate, long period NNW (330) swell will arrive Saturday with surf peaking near or below the High Surf Advisory (HSA) threshold. The swell will build late Saturday into Sunday. This brings a messy forecast scenario during this time as model guidance seems to be contaminated by merging strong NNE post- frontal wind swell leading to a larger and more north swell in the output than expected. None the less, HSA conditions will certainly be possible for north facing shores late Saturday through Monday.
Surf along E shores will remain small to moderate through Saturday. Strengthening post-frontal NNE trades may bring a rapid increase in wind waves and short period fresh swell for favored exposures Sunday through early next week, particularly over the western end of the state. A small south swell will slowly fade today through this weekend.

Fire weather

Increased relative humidity values and light to moderate trades will keep fire weather conditions below critical thresholds for the next several days. Temperature inversion heights near Maui and the Big Island will range from 6500 to 7500 feet elevation today.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 PM HST this evening for Maalaea Bay, Pailolo Channel, Alenuihaha Channel.

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