Hilo

Today: Showers likely, mainly before 1pm. Cloudy, with a high near 83. Calm wind becoming east 5 to 9 mph in the afternoon. Chance of precipitation is 70%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Showers likely, mainly after 7pm. Cloudy, with a low around 64. Light and variable wind becoming southwest around 5 mph. Chance of precipitation is 70%. New precipitation amounts of less than a tenth of an inch possible.

Saturday: Showers likely, mainly before 1pm. Cloudy, with a high near 84. Calm wind becoming east 5 to 8 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. Calm wind becoming west 5 to 9 mph. 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. Calm wind becoming east southeast around 5 mph after midnight. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Saturday: Scattered showers after noon. Partly sunny, with a high near 82. West wind 5 to 9 mph becoming calm in the afternoon. Chance of precipitation is 30%. New precipitation amounts of less than a tenth of an inch possible.

Waimea

Today: Scattered showers, mainly before 1pm. Mostly cloudy, with a high near 75. Windy, with a northeast wind 15 to 23 mph, with gusts as high as 32 mph. Chance of precipitation is 40%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Scattered showers, mainly after 7pm. Mostly cloudy, with a low around 50. Windy, with a northeast wind 18 to 23 mph, with gusts as high as 32 mph. Chance of precipitation is 40%. New precipitation amounts between a tenth and quarter of an inch possible.

Saturday: Scattered showers, mainly before 1pm. Mostly cloudy, with a high near 76. Windy, with a northeast wind 17 to 24 mph, with gusts as high as 34 mph. Chance of precipitation is 40%. New precipitation amounts of less than a tenth of an inch possible.

Kohala

Today: Frequent showers, mainly before noon. High near 67. Windy, with an east northeast wind 21 to 24 mph, with gusts as high as 34 mph. Chance of precipitation is 80%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Frequent showers. Low around 40. Very windy, with an east wind 24 to 29 mph increasing to 33 to 38 mph. Winds could gust as high as 55 mph. Chance of precipitation is 80%. New precipitation amounts of less than a tenth of an inch possible.

Saturday: Frequent showers, mainly before noon. High near 70. Windy, with an east wind 21 to 25 mph, with gusts as high as 36 mph. Chance of precipitation is 80%. New precipitation amounts of less than a tenth of an inch possible.

South Big Island

Today: Scattered showers before noon. Mostly sunny, with a high near 83. Windy, with an east wind 18 to 23 mph, with gusts as high as 30 mph. Chance of precipitation is 30%.

Tonight: Scattered showers after midnight. Partly cloudy, with a low around 69. Windy, with an east wind 23 to 26 mph, with gusts as high as 34 mph. Chance of precipitation is 30%.

Saturday: Scattered showers before noon. Mostly sunny, with a high near 83. Windy, with an east wind 24 to 28 mph, with gusts as high as 36 mph. Chance of precipitation is 30%.

Puna

Today: Frequent showers, mainly before noon. High near 82. West northwest wind 5 to 13 mph becoming east northeast in the afternoon. Chance of precipitation is 80%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Frequent showers. Low around 61. East northeast wind 5 to 10 mph becoming light and variable. Chance of precipitation is 80%. New precipitation amounts between a tenth and quarter of an inch possible.

Saturday: Frequent showers, mainly before noon. High near 82. Northwest wind 6 to 10 mph becoming northeast in the morning. Chance of precipitation is 80%. New precipitation amounts of less than a tenth of an inch possible.

Waikoloa

Today: Mostly sunny, with a high near 80. East southeast wind 8 to 11 mph becoming north in the morning.

Tonight: Mostly clear, with a low around 61. Breezy, with a north northeast wind 7 to 15 mph becoming east southeast in the evening. Winds could gust as high as 21 mph.

Saturday: Mostly sunny, with a high near 81. Breezy, with an east northeast wind 16 to 21 mph becoming light in the afternoon. Winds could gust as high as 29 mph.

Detailed Forecast

Synopsis

Moderate northeast trade winds will shift out of the east and become breezy later today through the weekend as high pressure builds to the north. Lingering moisture in the area combined with the trade winds will focus clouds and showers over windward and mountain locations through the weekend, especially during the overnight and early morning periods. Trade winds may diminish and shift out of the east-southeast early next week as a front and upper disturbance approach from the northwest. A modest increase in moisture ahead of this front will translate to increasing rainfall chances early next week.

Discussion

A residual moisture band associated with a dissipated front over the eastern end of the state will begin to shift back westward as a trough today through Saturday. Moderate northeast trade winds will shift out of the east and become breezy this afternoon through the weekend as it advances westward. This moisture axis (satellite-derived PWs up to around 1.5 inches) combined with the trades will support windward and mountain shower coverage, with the best chances through the overnight and early morning periods. An upper ridge and plenty of mid-level dry air in place, however, should limit accumulations. Guidance depicts drier air filling in from east to west behind the weak trough Saturday through Sunday with breezy easterly trades prevailing.
Although the forecast confidence begins lower due to some differences shown in the guidance, trade winds should trend down and potentially shift out of the east-southeast Sunday night into early next week as a shortwave trough digs southeast into the region. A weakness in the ridge is anticipated as its attendant cold front approaches from the northwest. If this evolves as projected, plenty of moisture pooling northward into the islands ahead of the front combined with light winds and falling upper heights will drive the rainfall chances up. The high sun angle going into the month of May combined with this scenario unfolding could translate to decent afternoon shower coverage over leeward and interior locations Monday through Tuesday.
Large model differences are shown by midweek with the GFS hanging the frontal boundary up west of the area and the European solution depicting it moving into the islands, stalling and dissipating with trades returning.

Aviation

Despite a brief break in coverage during the evening, clouds and showers have increased again overnight across Maui County. Therefore, AIRMET Sierra has been issued for tempo mountain obscuration for Maui and Molokai early this morning, and will likely need to be expanded to include Oahu as well as a residual moisture band shifts northwestward.
Light to moderate trade winds will become more easterly and prevail throughout the day today before becoming a bit stronger tonight and heading into the weekend. This will allow showers and isolated MVFR conditions to favor mainly north through east facing slopes and coasts of the islands for the next few days, particularly during the overnight and early morning periods.

Marine

High pressure northeast of the islands producing a tightening pressure gradient back toward the state has allowed for the return of trade winds. Today’s easterly trades will become areawide moderate to locally strong with winds holding at these magnitudes through the weekend. A Small Craft Advisory (SCA) will likely be be required tonight or early Saturday for the windier waters surrounding Maui County and south of the Big Island. The combination of strong trades and an incoming higher northwest swell will create rough weekend seas over many windward areas and island channels. Winds may diminish and veer more southeast early next week as an approaching front from the northwest weakens ridging over the islands.
Surf is trending up along along north and west facing shores as a mix of both medium period, north northwest and longer period, west northwest swells move around the islands. The north northwest swell should hold through the day before easing into the weekend. The long period, west northwest swell will fill in today and peak early Saturday surf near High Surf Advisory levels along smaller island northern and western exposed coasts. Surf along south facing shores will hold through the day as the latest long period, south southwest swell moves through. This swell will slowly fade over the weekend with mainly background southerly swell energy maintaining small south shore surf early next week. East facing shore surf will remain small through the afternoon. There will be a slight increase in east coast surf as strengthened trades push in a wind wave swell. A downward trend in east surf is expected next week as trades weaken.

HFO Watches/Warnings/Advisories

None.

Data Courtesy of NOAA.gov