Weather Forecast

Hawaii County Weather Forecast for March 19, 2021

March 19, 2021, 7:16 AM HST
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Hilo

Today: Showers likely, mainly before 1pm. Partly sunny, with a high near 79. Calm wind becoming north around 6 mph in the afternoon. Chance of precipitation is 60%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Showers likely, then showers and possibly a thunderstorm after 1am. Low around 66. Light and variable wind. Chance of precipitation is 80%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.

Saturday: Showers and possibly a thunderstorm. High near 79. Calm wind becoming north 5 to 7 mph in the afternoon. Chance of precipitation is 80%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.

Kona

Today: Scattered showers, mainly after noon. Mostly sunny, with a high near 81. East northeast wind around 6 mph becoming calm in the afternoon. Chance of precipitation is 40%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Isolated showers before midnight. Partly cloudy, with a low around 62. Calm wind becoming northeast 5 to 7 mph after midnight. Chance of precipitation is 20%.

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Saturday: Scattered showers and thunderstorms after noon. Mostly sunny, with a high near 80. West southwest wind 5 to 8 mph becoming calm in the afternoon. Chance of precipitation is 30%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.

Waimea

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Today: Scattered showers, mainly before noon. Mostly sunny, with a high near 76. Windy, with a northeast wind 25 to 29 mph, with gusts as high as 41 mph. Chance of precipitation is 40%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Scattered showers, then showers likely and possibly a thunderstorm after midnight. Mostly cloudy, with a low around 55. Windy, with an east northeast wind 23 to 25 mph, with gusts as high as 36 mph. Chance of precipitation is 60%. New rainfall amounts between three quarters and one inch possible.

Saturday: Showers likely and possibly a thunderstorm. Mostly cloudy, with a high near 76. Windy, with an east northeast wind 21 to 28 mph, with gusts as high as 39 mph. Chance of precipitation is 60%. New rainfall amounts between 1 and 2 inches possible.

Kohala

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Today: Scattered showers. Partly sunny, with a high near 72. Windy, with an east northeast wind 25 to 29 mph, with gusts as high as 41 mph. Chance of precipitation is 50%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Scattered showers, then showers and possibly a thunderstorm after midnight. Low around 48. Windy, with an east wind 25 to 28 mph, with gusts as high as 39 mph. Chance of precipitation is 80%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.

Saturday: Showers and possibly a thunderstorm. High near 72. Windy, with an east northeast wind 24 to 28 mph, with gusts as high as 39 mph. Chance of precipitation is 80%. New rainfall amounts between a tenth and quarter of an inch, except higher amounts possible in thunderstorms.

South Big Island

Today: Isolated showers before noon. Mostly sunny, with a high near 79. Windy, with an east wind around 29 mph, with gusts as high as 37 mph. Chance of precipitation is 20%.

Tonight: Isolated showers. Partly cloudy, with a low around 71. Windy, with an east northeast wind around 29 mph, with gusts as high as 37 mph. Chance of precipitation is 20%.

Saturday: Isolated showers before noon. Mostly sunny, with a high near 79. Windy, with an east northeast wind around 29 mph, with gusts as high as 38 mph. Chance of precipitation is 20%.

Puna

Today: Showers likely, mainly before noon. Partly sunny, with a high near 78. Northwest wind 6 to 9 mph becoming northeast in the afternoon. Chance of precipitation is 60%. New precipitation amounts of less than a tenth of an inch possible.

Tonight: Showers likely, then showers and possibly a thunderstorm after midnight. Low around 64. Northeast wind 7 to 9 mph becoming west northwest after midnight. Chance of precipitation is 90%. New rainfall amounts between three quarters and one inch possible.

Saturday: Showers and possibly a thunderstorm. High near 78. West northwest wind 7 to 11 mph becoming north northeast in the afternoon. Chance of precipitation is 90%. New rainfall amounts between 1 and 2 inches possible.

Waikoloa

Today: Isolated showers after noon. Sunny, with a high near 82. Windy, with a northeast wind 16 to 25 mph, with gusts as high as 36 mph. Chance of precipitation is 20%.

Tonight: Isolated showers after midnight. Mostly clear, with a low around 62. Breezy, with an east wind 17 to 22 mph decreasing to 10 to 15 mph in the evening. Winds could gust as high as 31 mph. Chance of precipitation is 20%.

Saturday: Isolated showers, then scattered showers and thunderstorms after noon. Partly sunny, with a high near 81. Windy, with an east northeast wind 11 to 16 mph increasing to 24 to 29 mph. Winds could gust as high as 41 mph. Chance of precipitation is 40%. New rainfall amounts between a quarter and half of an inch possible.

Detailed Forecast

Synopsis

The wet and gusty trade wind pattern will continue into the weekend due to an upper disturbance and bands of moisture moving through. Although most of the clouds and showers will continue to focus over windward and mountain locations, some will carry over into leeward areas periodically. Northeast trade winds will near advisory levels tonight into the weekend as another band of moisture moves in. Winds are forecast to diminish and shift out of the southerly direction early next week as another cold front and upper disturbance approach and move into the area.

Discussion

Persistent light to moderate rainfall continues to impact windward and mountain sections of the smaller islands this morning, which is expected to hold into the weekend due to an upper disturbance and bands of moisture moving through. Although the rainfall rates have remained on the light side, accumulations over the past 24-hrs (through early this morning) are quite impressive for the smaller islands with peak totals ranging from 4 to 7 inches. Streams have responded on Kauai and Oahu and will need to be monitored, especially when or if rainfall rates increase in these areas. Guidance depicts the next band of low-level moisture moving into the area tonight through Saturday, which will support the rainfall chances remaining up. Some of these showers will occasionally carry over into leeward sections – best chances being overnight through the early morning periods. Lowering upper heights associated with the upper trough could trigger a few thunderstorms, mainly over the eastern end of the state as the trough sharpens late tonight through Saturday.
In addition to the showery conditions, the gusty northeast trade winds may climb to advisory levels tonight through Saturday as the aforementioned band of moisture moves in. Saturated soils combined with wind gusts potentially reaching 45 mph could down trees and large branches.
Drier air following the previously discussed band of moisture moving through tonight through Saturday night could lead to improving conditions Sunday into Monday. This will likely be short-lived due to another cold front and upper low approaching early next week. Low-level winds will diminish and shift out of the southerly direction late Monday through Tuesday ahead of the front. Guidance depicts the front moving into the western end of the state by Wednesday, then stalling as the upper low hangs far north to northwest of the state. If this pattern materializes as projected, the potential for another round of wet conditions will increase statewide.

Aviation

A strong high pressure system passing north of the Hawaiian Islands will keep breezy to locally windy trade winds in the forecast into the weekend. An upper level disturbance moving into the region from the northwest will produce unstable passing showers with periods of MVFR conditions over most windward airfields into Saturday.
AIRMET Sierra for mountain obscuration remains in effect for north through east facing slopes of most islands and will likely remain in place through the early morning hours and decrease in coverage around 10 AM HST.
AIRMET Tango remains in effect for low-level turbulence over and south through west of island mountains. Tango will likely continue through Saturday due to the strong surface winds.

Marine

Little change to the marine elements with the morning package. Fresh to strong trade winds combined with north and northeasterly swells will continue to bring Small Craft Advisory (SCA) winds and/or seas to all the coastal waters through at least Saturday. The same combination will maintain advisory level surf along east facing shores, so a High Surf Advisory (HSA) remains posted as well.
High pressure to the north of the state will drive the fresh to strong trades into the weekend. As the high strengthens and moves to the east, we can expect an uptick in winds, with some of the windier locations seeing winds approaching gales. This uptick is expect tonight through Sunday.
A northerly swell will be on the decline, while a northeasterly swell arrives Saturday night. These swells combined with the trades will likely maintain both SCA and HSA conditions through Sunday.
Late Sunday and into early next week, the high will be pushed further to the east as a front approaches the state from the northwest. Expect winds to weaken and turn more southerly ahead of the front late Monday. The next northwest swell is expected to arrive Wednesday, which could bring advisory level surf to the north and west facing shores.

HFO Watches/Warnings/Advisories

High Surf Advisory until 6 PM HST Saturday for Kauai Windward, Oahu Koolau, Olomana, Molokai Windward, Maui Windward West, Windward Haleakala, Big Island North and East.
Small Craft Advisory until 6 PM HST Saturday for all Hawaiian waters,

Data Courtesy of NOAA.gov

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