Photo Credit: Jeni Ji Cousins

West Side

Today: Breezy. Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 79 to 84. Northeast winds 10 to 20 mph increasing to 20 to 25 mph in the afternoon. Chance of rain 40 percent.

Tonight: Partly cloudy. Breezy. Isolated showers in the evening, then scattered showers after midnight. Lows 66 to 73. Northeast winds 20 to 25 mph decreasing to 10 to 25 mph after midnight. Chance of rain 40 percent.

Wednesday: Breezy. Mostly sunny with isolated showers. Highs 78 to 83. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

South Side

Today: Breezy. Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs around 84. Northeast winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 40 percent.

Tonight: Breezy. Mostly cloudy with scattered showers in the evening, then mostly clear after midnight. Lows 62 to 72. Northeast winds 10 to 20 mph. Chance of rain 40 percent.

Wednesday: Breezy. Mostly sunny with isolated showers. Highs around 83. North winds 10 to 20 mph. Chance of rain 20 percent.

North Shore

Today: Breezy. Partly sunny with scattered showers. Highs 75 to 81 near the shore to around 63 near 5000 feet. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 50 percent.

Tonight: Mostly cloudy. Breezy. Numerous showers in the evening, then scattered showers after midnight. Lows around 67 near the shore to 46 to 53 near 5000 feet. East winds 10 to 20 mph. Chance of rain 70 percent.

Wednesday: Breezy. Partly sunny with scattered showers. Highs 74 to 80 near the shore to around 63 near 5000 feet. East winds 15 to 20 mph. Chance of rain 50 percent.

Central Maui

Today: Breezy. Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs around 83. Northeast winds 10 to 25 mph. Chance of rain 40 percent.

Tonight: Breezy. Mostly cloudy with scattered showers. Lows 63 to 68. Northeast winds 15 to 20 mph. Chance of rain 50 percent.

Wednesday: Breezy. Partly sunny with scattered showers. Highs around 82. Northeast winds 15 to 25 mph. Chance of rain 40 percent.

Upcountry

Today: Mostly sunny in the morning then becoming partly sunny. Breezy. Scattered showers. Highs around 59 at the visitor center to around 62 at the summit. East winds up to 20 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Breezy. Scattered showers. Lows around 46 at the visitor center to around 43 at the summit. East winds up to 20 mph increasing to 10 to 20 mph after midnight. Chance of rain 50 percent.

Wednesday: Mostly sunny in the morning then becoming partly sunny. Breezy. Scattered showers. Highs around 62 at the visitor center to around 64 at the summit. East winds 10 to 20 mph. Chance of rain 50 percent.

East Maui

Today: Breezy. Partly sunny with scattered showers. Highs 75 to 81 near the shore to around 63 near 5000 feet. East winds up to 20 mph increasing to 10 to 20 mph in the afternoon. Chance of rain 50 percent.

Tonight: Mostly cloudy. Breezy. Numerous showers in the evening, then scattered showers after midnight. Lows around 67 near the shore to 46 to 53 near 5000 feet. East winds 10 to 20 mph. Chance of rain 70 percent.

Wednesday: Breezy. Partly sunny with scattered showers. Highs 74 to 80 near the shore to around 63 near 5000 feet. East winds 15 to 20 mph. Chance of rain 50 percent.

Lanai City

Today: Breezy. Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 71 to 79. Northeast winds 10 to 25 mph. Chance of rain 30 percent.

Tonight: Breezy. Partly cloudy with isolated showers. Lows around 63. Northeast winds 10 to 25 mph. Chance of rain 20 percent.

Wednesday: Breezy. Mostly sunny with isolated showers. Highs 70 to 78. Northeast winds 10 to 25 mph. Chance of rain 20 percent.

Kaunakakai

Today: Breezy. Partly sunny with scattered showers. Highs 75 to 83. Northeast winds 10 to 25 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy in the evening then becoming partly cloudy. Breezy. Scattered showers. Lows 55 to 71. Northeast winds 10 to 20 mph. Chance of rain 50 percent.

Wednesday: Breezy. Mostly sunny with isolated showers. Highs 74 to 82. East winds 15 to 20 mph. Chance of rain 20 percent.

Detailed Forecast

Synopsis

A weakening cold front will stall over Kauai today increasing clouds and shower activity over Kauai County. The island of Oahu will also see increasing shower trends as increasing trade winds push unstable cloud bands over the island. Breezy to locally windy trade winds will build in and spread increasing shower trends from west to east over all islands today, as a high pressure system strengthens north of the state and the front diminishes over Kauai. These breezy to locally windy trades will continue into Friday. Passing trade wind showers will continue to develop this week favoring the windward and mountain areas of each island through Friday. Drier trends are forecast for the upcoming weekend.

Discussion

Satellite imagery shows the leading edge of a cold front is moving into Niihau and Kauai this morning with cooling cloud tops showing rising cloud tops and increasing shower activity along this frontal cloud band. The islands in Kauai county will see increasing rainfall trends with periods of moderate to heavy showers through the day today as the frontal cloud band stalls over the county and breezy trade winds push clouds up the windward and mountain slopes of Kauai. The latest radar imagery is consistent with the short term rainfall trend for Kauai County. Local radar continues to show showers spreading as far east as Molokai, increasing showers will continue to spread eastward to the other islands through the day.
Strengthening trade winds will spread eastward across the island chain today as the high pressure ridge builds north of the state. A cold front will stall near Kauai today with unstable cloud bands drifting over the western islands. Enough instability will allow a few thunderstorms to develop along the frontal cloud zone near Kauai through the evening hours. Strengthening trade winds will keep these shower bands moving through the western islands and the threat for widespread flooding with this stalled front remains low. However, localized flooding may occur today over Kauai if heavy shower bands begin to line up, or train, over windward mountain slopes.
An upper level disturbance will develop over the state as the surface front diminishes into a trough today and Wednesday, enhancing shower activity mainly over windward and mountain sections of all islands into Friday. The added instability from this upper trough will combine forces with the breezy to locally windy trade winds forcing clouds to rain out along the north through east facing mountain slopes of each island. Some of the stronger showers will drift into leeward areas during this time period, however the highest rainfall totals are forecast over the windward and mountain zones.
Long range weather model solutions are showing drier trends by this weekend as the upper level trough is replaced by a more stable upper level ridge. Expect drier weather trends on Saturday and Sunday with moderate to breezy trade winds. Any brief passing showers that develop will favor the windward areas in the overnight to early morning hours.
Short and long range models are in good agreement with the current weather forecast and little changes were needed to the overnight weather grid package.

Aviation

Radar trends continue to show an area of locally heavy showers approaching Kauai from the northwest, while isolated to scattered showers continue over the central and eastern islands. Satellite continued to show increasing low/mid cloud cover over the state this morning, while the leading edge of the dense upper cloud deck continues to overspread the western portions of the state. The front northwest of the islands will continue to increase moisture and showers, and possibly a thunderstorm over Kauai, through tonight. Additionally, northeasterly winds will continue to expand across the state from west to east, which will increase chances for showers across windward zones. Overall, conditions will continue to deteriorate toward MVFR, possibly periods of IFR, cigs and vsby across Kauai and windward zones of the central islands through today, while mainly VFR conditions continue for sheltered areas.
AIRMET Sierra is in affect for tempo mountain obscuration for western and central islands, likely expanding this afternoon as showers and low lvl clouds develop. AIRMET Tango is in effect for low-level turbulence across much of the region and is expected to continue through tonight. AIRMET Zulu is in effect for Kauai for mod rime ice in precipitation, in response to an area of deep layer moisture in a region of dropping freezing levels. Mod rime ice chances will likely continue into this evening and possibly expand eastward.

Marine

Northeast to east trade winds will increase, especially around Kauai, as a front pushes in from the northwest. The front will stall later today in the vicinity of Kauai and gradually dissipate through Thursday or Friday as strong high pressure builds northwest of the state. Trade winds will strengthen to fresh to strong levels through the day, especially along and just north of the front, and persist through at least Thursday. A Small Craft Advisory (SCA) was issued earlier for all waters through Wednesday afternoon; and, additionally, a thunderstorm or two could develop along the front.
The current northwest swell is expected to peak today, but will be reinforced by a pulse of north swell. A High Surf Advisory (HSA) in effect for this episode along many north and west facing shores will continue at least through this afternoon. On the Big Island, effects from the initial northwest swell will be limited to a slight increase in surf along west facing shores this morning, but north facing shores will experience a more significant rise as the north swell fills in late today and Wednesday, though advisory level surf is not expected. The north swell will gradually decline Wednesday through Friday.
Rises are expected on east and south facing shores as well. Wind swell will build as the trade winds increase today and Wednesday, but the islands will lie near the eastern edge of the fetch of strong trade winds, which will limit the growth of the local seas. The latest guidance shows the rough trade wind swell could push east shore surf on Kauai near the HSA level as early as later today, but seas are projected to build to around seasonal average elsewhere. That said, some wrapping north swell could lead to elevated east shore surf, as well as surges in Kahului and Hilo Harbors. The trade wind swell will persist beyond midweek, and the combined seas from the trade wind swell and the northwest to north swell will likely require the SCA to continue through Thursday. In addition, background south shore surf will be interrupted by a small south-southwest swell arriving this afternoon and peaking Wednesday into Thursday.

HFO Watches/Warnings/Advisories

High Surf Advisory until 6 PM HST this evening for north and west facing shores of Niihau, Kauai, Oahu, Molokai, and north facing shores of Maui.
Small Craft Advisory until 6 PM HST Wednesday for all Hawaiian waters,

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Data Courtesy of NOAA.gov