Photo Credit: Tyler Rooke

West Side

Today: Breezy. Partly sunny in the morning, then mostly sunny with isolated showers in the afternoon. Highs 77 to 86. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Breezy. Isolated showers. Lows 65 to 71. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Saturday: Partly sunny in the morning then becoming mostly sunny. Breezy. Isolated showers. Highs 76 to 85. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

South Side

Today: Mostly sunny. Breezy. Highs around 86. North winds up to 15 mph increasing to 10 to 20 mph in the afternoon.

Tonight: Partly cloudy. Breezy. Lows 63 to 70. Northeast winds 10 to 20 mph.

Saturday: Mostly sunny. Highs around 86. Northeast winds 10 to 15 mph.

North Shore

Today: Mostly cloudy. Breezy. Scattered showers early in the morning. Isolated showers late in the morning, then scattered showers in the afternoon. Highs 75 to 81 near the shore to around 65 near 5000 feet. East winds up to 20 mph becoming 10 to 15 mph in the afternoon. Chance of rain 50 percent.

Tonight: Mostly cloudy. Scattered showers early in the evening, then numerous showers late in the evening. Frequent showers after midnight. Lows around 67 near the shore to around 49 near 5000 feet. East winds up to 15 mph. Chance of rain 80 percent.

Saturday: Mostly cloudy. Breezy. Frequent showers in the morning, then scattered showers in the afternoon. Highs 75 to 82 near the shore to around 65 near 5000 feet. Northeast winds 10 to 20 mph. Chance of rain 80 percent.

Central Maui

Today: Partly sunny in the morning then becoming mostly sunny. Breezy. Highs 80 to 86. Northeast winds 10 to 20 mph.

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Breezy. Isolated showers. Lows 63 to 68. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Saturday: Breezy. Partly sunny with isolated showers in the morning, then mostly sunny in the afternoon. Highs 80 to 85. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Upcountry

Today: Partly sunny with scattered showers. Highs around 59 at the visitor center to around 53 at the summit. East winds up to 15 mph shifting to the northeast in the afternoon. Chance of rain 50 percent.

Tonight: Partly cloudy with scattered showers. Lows around 45 at the visitor center to around 40 at the summit. East winds up to 10 mph. Chance of rain 50 percent.

Saturday: Mostly sunny in the morning then becoming partly sunny. Scattered showers. Highs around 60 at the visitor center to around 54 at the summit. Northeast winds around 10 mph. Chance of rain 50 percent.

East Maui

Today: Mostly cloudy. Breezy. Scattered showers early in the morning. Isolated showers late in the morning, then scattered showers in the afternoon. Highs 75 to 81 near the shore to around 65 near 5000 feet. East winds up to 20 mph becoming 10 to 15 mph in the afternoon. Chance of rain 50 percent.

Tonight: Mostly cloudy. Scattered showers early in the evening, then numerous showers late in the evening. Frequent showers after midnight. Lows around 67 near the shore to around 49 near 5000 feet. East winds up to 15 mph. Chance of rain 80 percent.

Saturday: Mostly cloudy. Breezy. Frequent showers in the morning, then scattered showers in the afternoon. Highs 75 to 82 near the shore to around 65 near 5000 feet. Northeast winds 10 to 20 mph. Chance of rain 80 percent.

Lanai City

Today: Mostly sunny in the morning then becoming mostly cloudy. Breezy. Isolated showers. Highs 71 to 79. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Tonight: Breezy. Mostly cloudy with isolated showers early in the evening, then partly cloudy in the late evening and overnight. Lows around 63. Northeast winds 10 to 25 mph. Chance of rain 20 percent.

Saturday: Mostly sunny in the morning, then mostly cloudy with isolated showers in the afternoon. Highs 72 to 79. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Kaunakakai

Today: Partly sunny. Breezy. Highs 66 to 86. Northeast winds 10 to 20 mph.

Tonight: Partly cloudy in the evening then becoming mostly cloudy. Breezy. Isolated showers. Lows 55 to 71. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Saturday: Partly sunny. Breezy. Isolated showers in the morning. Highs 67 to 85. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Moderate to locally breezy trade winds will weaken slightly into the weekend. An upper trough over the region will help enhance shower coverage and rainfall intensity at times through tonight. Isolated thunderstorms are possible over portions of the Big Island today. A trend toward more stable and drier conditions is then expected this weekend, with lingering trade wind flow focusing showers across mainly windward and mauka areas.

Discussion

Current radar shows showers remain scattered across the state this morning in response to lingering trade wind flow and the weak upper low in the vicinity. Radar estimates show a few heavier showers remain embedded in the flow, especially across Oahu and Kauai.
Today through tonight…have increased the areal coverage of showers across the western half of the state, as an upper trough (associated with an upper low northeast of the state) begins to sweep in from the northwest. The dynamics associated with this upper trough will combine with a band of enhanced moisture (satellite imagery PW values 1.40″ to 1.50″) streaming into the state from the east. Low level streamline convergence and cooling temperatures moving in aloft, will help support embedded higher rainfall rates across the islands at times today. Stability indices (SW index) and thunderstorm probabilities show enough instability across mainly the eastern end of the state to support a chance of afternoon convection. Some afternoon sun and steepening lapse rates should enhance the chances over Big Island, therefore will maintain the isolated thunderstorm chance over leeward and upslope portions. Otherwise trade winds should maintain a majority of showers to favored windward areas.
The persistent upper low, which has been anchored over the region since earlier in the week, will continue to drift northeastward tonight. This will allow a narrow upper ridge to approach from the northwest tonight, and begin the trend toward drier and more stable conditions.
Saturday through Sunday…a strong area of high pressure well north of the islands will maintain trade winds through the weekend. The winds will trend more southeast and weaken slightly Sunday, as a surface boundary approaches from the northwest. At upper levels, the low will continue to slowly drift northeast of the state allowing an upper ridge and more stable airmass to organize across the islands. The fairly stable and dry airmass (modeled PW values 1.30″ or less) will maintain a majority of showers across windward areas with the greatest areal coverage of showers expected at night through early morning.
Monday through next week…global models are in fairly consistent agreement with surface and upper level features influencing the state through the first half of the week. A narrow upper level ridge, which developed over the islands over the weekend, will slowly push eastward through the week while a weakly organized upper trough, associated with a strong upper low well northwest of the state, slowly drifts eastward. At the surface, low pressure moving well north of the state will drag a front into the islands through midweek, potentially increasing shower coverage and rainfall rates Tuesday and Wednesday. The second half of the week, model solutions begin to diverge with the overall evolution and movement of surface and upper level features.

Aviation

Moderate to locally breezy trade winds will continue today. Current satellite imagery and radar show scattered clouds and showers moving through the islands from the east with the focus of the showers being over windward and mauka areas. A few thunderstorms have been observed over the waters far South and East of Oahu and Kauai and are expected to stay offshore. An isolated thunderstorm will remain possible over the Big Island slopes this afternoon as instability from an upper level low lingers. Shower activity is expected to continue favoring windward and mauka areas through the TAF period with a few showers drifting to leeward areas. A few of these showers will bring isolated MVFR conditions. Overall VFR conditions will prevail.
AIRMET Tango remains in effect for moderate low level turbulence over and downwind of higher terrain across all islands.

Marine

A 1032 mb high pressure cell centered approximately 1,200 miles north northeast of Oahu will become absorbed by a new high expanding down from the Aleutian Islands. This will weaken the high and relax the upstream pressure gradient over the islands as the high slowly meanders southeast Saturday. The current SCA has been scaled back area-wise to now just include the Alenuihaha and Pailolo Channels and Maalaea Bay. Winds should briefly drop below SCA thresholds across the entire region this evening. Following a Saturday of relatively light trade flow, a trough developing west of the state along with a surface high establishing itself far northeast of the area will veer returning fresh to locally strong trades toward the southeast Sunday into Tuesday.
A slowly diminishing moderate size, short period northeast (30-40 degree) swell that popped in yesterday will maintain chest to near head high surf along many north and northeast-facing shorelines through the day. A small, medium period northwest (320 degree) swell is scheduled to arrive later today as it has not shown up at the far northwest offshore buoys before sunrise. This swell is forecast to fill in through tonight and peak on Saturday. This swell will hold waist to near head high surf along many north-facing shores, near knee to waist high surf along west-facing shores Saturday. East-facing shores will experience continued choppy conditions through today in response to several days of an upstream fresh trade fetch. Surf along east-facing shores will slowly subside going into this weekend as trades fall off a notch. Small, background south swell energy will maintain knee to chest high surf along many southern shores. A very small, medium period south southwest bump in swell arriving this morning will result in a small boost in weekend surf.

HFO Watches/Warnings/Advisories

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

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Data Courtesy of NOAA.gov