Photo Credit: Tyler Rooke

West Side

Today: Mostly cloudy. Breezy. Isolated showers in the morning. Highs 70 to 77. Northeast winds 10 to 25 mph shifting to the east up to 25 mph in the afternoon. Chance of rain 20 percent.

Tonight: Mostly cloudy. Breezy. Lows 63 to 69. East winds up to 20 mph.

Tuesday: Partly sunny with isolated showers. Highs 76 to 82. East winds up to 10 mph in the morning becoming light. Chance of rain 20 percent.

South Side

Today: Cloudy and breezy. Highs around 78. Northeast winds up to 20 mph.

Tonight: Mostly cloudy. Lows around 64. North winds up to 15 mph.

Tuesday: Partly sunny. Isolated showers in the afternoon. Highs around 82. Northwest winds up to 10 mph in the morning becoming light. Chance of rain 20 percent.

North Shore

Today: Cloudy and breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 70 to 76 near the shore to around 56 near 5000 feet. East winds 10 to 25 mph. Chance of rain 70 percent.

Tonight: Breezy. Mostly cloudy with numerous showers. Lows 61 to 67 near the shore to around 46 near 5000 feet. East winds 10 to 20 mph. Chance of rain 70 percent.

Tuesday: Mostly cloudy. Breezy. Showers in the morning, then numerous showers in the afternoon. Highs 74 to 79 near the shore to around 58 near 5000 feet. East winds up to 20 mph. Chance of rain 90 percent.

Central Maui

Today: Mostly cloudy. Breezy. Isolated showers in the morning. Highs 74 to 79. East winds 10 to 25 mph. Chance of rain 20 percent.

Tonight: Breezy. Mostly cloudy with isolated showers. Lows 62 to 67. East winds 10 to 20 mph decreasing to up to 20 mph after midnight. Chance of rain 20 percent.

Tuesday: Partly sunny. Isolated showers in the morning, then scattered showers in the afternoon. Highs 78 to 83. East winds up to 15 mph. Chance of rain 40 percent.

Upcountry

Today: Breezy. Cloudy with scattered showers. Highs 52 to 65. East winds up to 20 mph. Chance of rain 50 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 38 to 51. Southeast winds 10 to 20 mph. Chance of rain 50 percent.

Tuesday: Breezy. Partly sunny with scattered showers. Highs 50 to 64. Southeast winds up to 20 mph shifting to the west up to 10 mph in the afternoon. Chance of rain 50 percent.

East Maui

Today: Cloudy and breezy. Numerous showers in the morning, then scattered showers in the afternoon. Highs 70 to 76 near the shore to around 56 near 5000 feet. East winds 10 to 25 mph. Chance of rain 70 percent.

Tonight: Breezy. Mostly cloudy with numerous showers. Lows 61 to 67 near the shore to around 46 near 5000 feet. East winds 10 to 20 mph. Chance of rain 70 percent.

Tuesday: Mostly cloudy. Breezy. Showers in the morning, then numerous showers in the afternoon. Highs 74 to 79 near the shore to around 58 near 5000 feet. East winds up to 20 mph. Chance of rain 90 percent.

Lanai City

Today: Mostly cloudy. Breezy. Isolated showers in the afternoon. Highs 68 to 75. Northeast winds 10 to 20 mph decreasing to up to 20 mph in the afternoon. Chance of rain 20 percent.

Tonight: Mostly cloudy. Lows around 63. Northeast winds up to 10 mph.

Tuesday: Partly sunny. Scattered showers in the afternoon. Highs 67 to 74. Light winds. Chance of rain 30 percent.

Kaunakakai

Today: Cloudy in the morning then becoming partly sunny. Breezy. Highs 67 to 77. East winds 10 to 20 mph.

Tonight: Mostly cloudy. Breezy. Lows 59 to 71. East winds 10 to 20 mph.

Tuesday: Partly sunny. Scattered showers in the afternoon. Highs 71 to 81. East winds 10 to 15 mph in the morning becoming light. Chance of rain 40 percent.

Detailed Forecast

Synopsis

An upper level disturbance will move northeastward away from the island chain from Tuesday into Wednesday with decreasing high clouds and shower trends. A strong high pressure system north of the islands will continue to drift eastward through the first half of the week. Expect breezy trade winds to continue through Monday night, and then show decreasing trends into the light to moderate range from Tuesday into Wednesday. A weakening cold front will drift through the islands by Wednesday night with moderate to locally breezy north- northeasterly trade winds building in through Thursday across the Hawaii region. Relatively cooler and drier conditions will fill in after frontal passage.

Discussion

Satellite imagery this morning continues to show a subtropical jet stream and an upper level low over the islands. These two upper level features will continue to produce high clouds and periods of showers, favoring windward and mountain areas in the overnight to early morning hours through Tuesday. The low pressure system will move northeastward away from the island chain from Tuesday into Wednesday with decreasing high clouds and shower trends.
A strong high pressure system north of the islands will continue to drift eastward, producing breezy trade winds through tonight with decreasing trends into the light to moderate range from Tuesday into Wednesday. Lighter large scale winds will allow local scale land and sea breezes to develop from Tuesday through Wednesday. Brief showers may develop during the afternoon to early evening time periods over mountain and island interior sections.
More stability showing up in the latest model guidance as compared to slightly unstable environment on past model runs decreases the chances for heavy showers and thunderstorms this week. However, deeper moisture will produce some snowfall over the highest summits of Mauna Kea and Mauna Loa with light accumulations forecast through Tuesday, then a few inches of snowfall are possible from Tuesday night through Wednesday. A Winter Weather Advisory for snow may be needed for this event.
A weak and shallow cold front will drift through the islands by Wednesday night, moderate to locally breezy north-northeasterly trade winds will build in across the Hawaii region through Thursday. Shower trends will briefly increase along northern and northeastern slopes as the front passes each island. Relatively cooler and drier conditions will fill in after frontal passage as a more stable air mass moves into the region. Wind directions will veer from the northeast direction by Friday, with lighter easterly winds expected by the weekend with a hybrid land and sea breeze weather pattern.

Aviation

An area of surface high pressure north of the state will generate breezy east northeasterly trades today across the islands and cause tempo moderate turbulence above the leeward terrain. See AIRMET Tango below for details. A weak upper level trough west of the state will help usher in mid and upper level clouds from the southwest.
Showers will mainly be limited to windward locations with isolated showers for leeward sides. Brief periods of MVFR ceilings and visibility may accompany any of the more robust showers.
AIRMET Sierra has been issued for north through east portions of the Big Island above 2500 feet for tempo mountain obscuration due to clouds and showers.
AIRMET Tango remains in effect below 7000 feet over and south through west of mountains for tempo moderate turbulence. AIRMET Tango also remains in effect for tempo moderate turbulence aloft between FL200-350 due to the presence of a branch of the subtropical jet over the islands (with isolated pockets of severe turb possible). The turbulence aloft is expected to continue through at least this afternoon.

Marine

Fresh to strong easterly trades will continue through tonight, then slowly ease and shift out of east-southeast Tuesday as a cold front approaches from the northwest. Guidance shows the winds diminishing Tuesday night through Wednesday with the background flow shifting out of the west-northwest through the day Wednesday as the front closes in. Expect land and sea breeze conditions during this short window of time, beginning over the western end of the state Tuesday afternoon, then statewide Wednesday. Moderate to locally fresh northerly winds will fill in as the front advances down the island chain late Wednesday through Thursday, then shift out of the northeast Friday as the ridge noses eastward into area behind the front.
Surf along exposed north and west facing shores will remain up through the first half of the week as small to moderate, overlapping north-northwest swells move through. The next pulse has been holding steady within the 18-22 s bands overnight at the Waimea buoy (similar observations shown at the offshore buoys), and will build later today through Tuesday as the swell peaks. A gradual downward trend will follow into midweek.
A more significant northwest to north-northwest swell is expected late Wednesday night through the second half of the week in response to a developing hurricane force low currently analyzed around 2000 nm northwest of the islands across the far northwest Pacific. Guidance shows a good sized area of gale- to storm-force winds focused at the state within the 310-340 degree directional bands through the first half of the week as the system advances eastward. Surf heights could reach warning levels during the peak of this event late Thursday through Friday if this scenario evolves as predicted.
Surf along south facing shores will remain up through Tuesday as a south-southwest swell moves through. Observations at the nearshore PacIOOS Barbers buoy are reflecting this fresh swell this morning within the 18-22 s bands. This source should peak through the day, then ease Tuesday into midweek.
Surf along east facing shores will remain rough through tonight, then begin to ease Tuesday through midweek as the trades diminish. The small trend will hold through the second half of the week, except for areas exposed to north-northwest swells later this week.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 AM HST Tuesday for Oahu Leeward Waters, Kaiwi Channel, Maui County Leeward Waters, Maalaea Bay, Pailolo Channel.
Small Craft Advisory until 6 PM HST Tuesday for Maui County Windward Waters, Alenuihaha Channel, Big Island Windward Waters, Big Island Leeward Waters, Big Island Southeast Waters.

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Data Courtesy of NOAA.gov