Hilo

Today: Showers likely, mainly before 1pm. Cloudy, with a high near 81. Light and variable wind becoming east 5 to 7 mph in the afternoon. Chance of precipitation is 60%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Showers likely, mainly after 1am. Cloudy, with a low around 63. Calm wind becoming west southwest around 5 mph. Chance of precipitation is 70%. New precipitation amounts of less than a tenth of an inch possible.

Monday: Showers likely, mainly before 1pm. Mostly cloudy, with a high near 82. Light and variable wind becoming east southeast 6 to 11 mph in the afternoon. Chance of precipitation is 70%. New precipitation amounts of less than a tenth of an inch possible.

Kona

Today: Scattered showers after noon. Partly sunny, with a high near 82. Light and variable wind becoming west 5 to 8 mph in the morning. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Scattered showers before midnight. Mostly cloudy, with a low around 63. North northwest wind around 5 mph becoming calm in the evening. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Monday: Scattered showers after noon. Partly sunny, with a high near 82. Light and variable wind becoming west northwest 6 to 11 mph. Chance of precipitation is 40%. New precipitation amounts of less than a tenth of an inch possible.

Waimea

Today: Scattered showers, mainly before noon. Mostly cloudy, with a high near 76. Breezy, with a northeast wind 20 to 22 mph, with gusts as high as 31 mph. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Scattered showers. Mostly cloudy, with a low around 49. Breezy, with an east northeast wind 16 to 21 mph decreasing to 7 to 12 mph after midnight. Winds could gust as high as 29 mph. Chance of precipitation is 40%. New precipitation amounts between a tenth and quarter of an inch possible.

Monday: Scattered showers. Mostly cloudy, with a high near 75. North northeast wind 5 to 7 mph becoming calm in the morning. Chance of precipitation is 50%. New precipitation amounts between a tenth and quarter of an inch possible.

Kohala

Today: Scattered showers. Cloudy, with a high near 69. Windy, with an east wind 22 to 24 mph, with gusts as high as 34 mph. Chance of precipitation is 50%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Showers likely, mainly after midnight. Cloudy, with a low around 39. Windy, with an east wind 19 to 24 mph becoming south 5 to 10 mph after midnight. Winds could gust as high as 34 mph. Chance of precipitation is 70%. New precipitation amounts of less than a tenth of an inch possible.

Monday: Showers likely, mainly before noon. Mostly cloudy, with a high near 68. Calm wind becoming east southeast around 6 mph. Chance of precipitation is 70%. New precipitation amounts of less than a tenth of an inch possible.

South Big Island

Today: Mostly sunny, with a high near 83. Windy, with an east wind around 25 mph, with gusts as high as 32 mph.

Tonight: Scattered showers after midnight. Partly cloudy, with a low around 69. Windy, with an east wind 17 to 25 mph, with gusts as high as 32 mph. Chance of precipitation is 30%.

Monday: Scattered showers, mainly before noon. Mostly sunny, with a high near 83. Breezy, with an east wind 13 to 20 mph, with gusts as high as 24 mph. Chance of precipitation is 30%.

Puna

Today: Showers likely, mainly before noon. Cloudy, with a high near 79. East northeast wind 5 to 11 mph. Chance of precipitation is 60%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Showers likely, mainly after midnight. Cloudy, with a low around 61. Northeast wind 5 to 8 mph becoming calm in the evening. Chance of precipitation is 70%. New precipitation amounts between a tenth and quarter of an inch possible.

Monday: Showers likely, mainly before noon. Mostly cloudy, with a high near 80. Light and variable wind becoming east southeast 5 to 10 mph in the morning. Chance of precipitation is 70%. New precipitation amounts between a tenth and quarter of an inch possible.

Waikoloa

Today: Mostly sunny, with a high near 80. Northeast wind 9 to 14 mph, with gusts as high as 18 mph.

Tonight: Mostly clear, with a low around 61. East wind 8 to 11 mph.

Monday: Scattered showers after noon. Increasing clouds, with a high near 81. West northwest wind 6 to 11 mph becoming light and variable in the afternoon. Chance of precipitation is 40%. New precipitation amounts of less than a tenth of an inch possible.

Detailed Forecast

Synopsis

Breezy easterly trade winds will prevail into Monday, with clouds and showers favoring windward and mountain locations. Trade winds will weaken and shift out of the east-southeast late Monday through Tuesday as an upper disturbance moves into the area from the northwest and a trough forms near Kauai. Warm and humid conditions with increasing rainfall chances are expected Monday through Tuesday, especially for the western end of the state. A return of moderate to breezy easterly trade wind conditions will be possible Wednesday through the second half of the week.

Discussion

Short-term guidance remains in good agreement and depicts the subtropical ridge remaining anchored north of the area into Monday, which supports the breezy easterly trades continuing. Clouds and showers will favor windward and mountain areas, especially overnight through the early morning periods. An upper ridge and plenty of mid-level dry air in place should limit accumulations.
Trade winds are expected to trend down and shift out of the east- southeast late Monday through Tuesday as a shortwave trough digs southeastward into the region and closes off an upper low to the west by Tuesday. Guidance supports a surface trough forming in response and setting up near or over the western end of the state Monday night into Tuesday. Although there remain some differences between the various model solutions (GFS being the wetter option), all support a moistening trend with PWs climbing into the 1.5 to 1.75 inch range. This moisture combined with light winds and falling upper heights will drive the rainfall chances up, with the best chances being over the western end of the state closer to the deep layer moisture and instability.
Breezy trade winds are forecast to return through the second half of the week as high pressure builds in to our north. Guidance depicts the previously discussed upper low to the west drifting eastward over the islands. This upper low combined with a sufficient amount of moisture lingering in the area will keep the rainfall chances up, especially over windward and mountain locations overnight and through the early morning hours.

Aviation

High pressure northeast of the state will keep moderate to breezy trades in place during the next 24 hours. Clouds and showers will favor windward and mauka areas, with a stray shower reaching leeward areas from time to time.
AIRMET Tango remains in effect for moderate low level turbulence over and downwind of the terrain of all islands. This AIRMET will likely continue through this evening.
AIRMET Sierra may be needed for mountain obscuration across windward sections of the Big Island and Maui later this morning.

Marine

Locally strong trade winds, supported by surface high pressure centered to the distant NE of the islands, will continue to warrant a Small Craft Advisory for the windier zones around Maui and the Big Island through tonight. Thereafter, a sharpening surface trough N of the islands will lead to a loosening of the pressure gradient over the area, with trade winds weakening and potentially veering to the ESE Monday night and Tuesday. As the surface trough shifts W Tuesday night and Wednesday, high pressure will build to the N of the islands, and E to ESE trade winds will likely surge in response.
A gradually diminishing WNW swell will keep surf elevated, but below advisory-levels, along exposed N and W facing shores today, with wave heights slowly diminishing through Monday. Little additional swell energy from the NW is expected through the week, and surf will remain below advisory levels along all shores through the week. Although short-period surf along E facing shores will likely increase as trade winds increase later in the week, a limited upstream fetch will keep surf below advisory levels. Small surf will persist along S facing shores.

HFO Watches/Warnings/Advisories

Small Craft Advisory until 6 AM HST Monday for Maalaea Bay, Pailolo Channel, Alenuihaha Channel, Big Island Leeward Waters, Big Island Southeast Waters.

Data Courtesy of NOAA.gov