West Side

Today: Mostly sunny with isolated showers. Highs around 79. East winds up to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Isolated showers in the evening. Lows 65 to 72. East winds up to 15 mph. Chance of rain 20 percent.

Monday: Mostly sunny. Breezy. Highs 77 to 82. East winds 10 to 20 mph.

South Side

Today: Mostly sunny. Isolated showers in the afternoon. Highs around 83. North winds up to 15 mph. Chance of rain 20 percent.

Tonight: Mostly clear. Lows 63 to 73. North winds up to 10 mph.

Monday: Sunny. Highs around 85. North winds up to 15 mph shifting to the northeast in the afternoon.

North Shore

:

Central Maui

Today: Mostly sunny. Highs 78 to 84. Northeast winds up to 15 mph.

Tonight: Mostly clear. Lows 63 to 69. East winds up to 15 mph.

Monday: Sunny and breezy. Highs 80 to 85. Northeast winds 10 to 20 mph.

Upcountry

Today: Mostly sunny in the morning then becoming partly sunny. Scattered showers. Highs around 58 at the visitor center to around 63 at the summit. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Partly cloudy with scattered showers. Lows 41 to 53. East winds up to 10 mph. Chance of rain 50 percent.

Monday: Sunny with scattered showers. Highs around 59 at the visitor center to around 66 at the summit. Northeast winds up to 10 mph shifting to the east in the afternoon. Chance of rain 50 percent.

East Maui

Today: Partly sunny with scattered showers. Highs around 79 near the shore to around 63 near 5000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Tonight: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Lows around 69 near the shore to around 49 near 5000 feet. Southeast winds up to 15 mph. Chance of rain 50 percent.

Monday: Mostly sunny. Breezy. Isolated showers in the morning, then scattered showers in the afternoon. Highs around 79 near the shore to around 63 near 5000 feet. East winds up to 20 mph. Chance of rain 40 percent.

Lanai City

Today: Mostly sunny with isolated showers in the morning, then partly sunny with scattered showers in the afternoon. Highs 70 to 78. Northeast winds up to 10 mph. Chance of rain 30 percent.

Tonight: Partly cloudy with isolated showers. Lows around 64. Northeast winds up to 10 mph. Chance of rain 20 percent.

Monday: Mostly sunny. Breezy. Isolated showers in the morning. Highs 71 to 79. Northeast winds 10 to 20 mph. Chance of rain 20 percent.

Kaunakakai

Today: Mostly sunny with isolated showers. Highs 68 to 85. Northeast winds up to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Isolated showers in the evening. Lows 56 to 71. East winds 10 to 15 mph. Chance of rain 20 percent.

Monday: Mostly sunny. Highs 69 to 86. East winds 10 to 15 mph.

Detailed Forecast

Synopsis

Light to moderate trades with embedded showers favoring predominately windward and mauka areas are expected through the day, followed by drier and more stable conditions through the first half of the week. Winds will begin ease by Wednesday and veer southerly in response to an advancing front northwest of the islands. This front is expected to move over the islands during the latter half of the week, potentially increasing shower activity.

Discussion

Latest radar data indicate the volcanic ash from Kilauea's Halemaumau Crater during episode 38 that started decreasing yesterday evening, has further decreased this morning. Radar observations as of 13z (3am HST LT) show the plume now at approximately 10000 feet mean sea level (MSL), with light ashfall possible southwestward within 5 miles from the volcano source.
Moderate trades continue to ease as an upper-level trough propagates into the vicinity of the islands. Latest satellite water vapor imagery clearly depicts a sub-tropical jet just north and west of Kauai producing two distinct upper-level lows; one on either side of the Hawaiian Islands. The more mobile low west of the islands will begin to dig southwestward away from the state, resulting in little impact. Conversely, the more intrusive, eastern low will result in a bit of instability, which may produce some brief enhanced shower activity focused over predominately windward and mauka areas.
Additionally, a well-defined band of moisture can be seen on satellite imagery is anticipated to bring showers mainly to windward areas of Big Island and Maui initially this morning. However, trends displayed on an American model (GFS) cross section of Hawaii portrays wetter conditions moving up the island chain to Molokai and Oahu late this morning to early afternoon. Overall precipitation accumulation will be on the lighter side, but some locations may fetch a tenth to upwards of a quarter of an inch of rainfall.
Model guidance of the GFS and European model (ECMWF) show the aforementioned low eventually strengthens and forms a closed low tomorrow, and slowly meanders away from the Hawaiian Islands. Ridging quickly builds in in its wake, allowing dry and stable conditions to return. This will open the doors to moderate trades reestablishing, with the more typical trade showers across windward and mauka areas with exception for the Kona slopes of the Big Island, where typical sea-breeze induced cloud buildups and showers will be possible during the day.
Toward the latter end of the week, model guidance introduces a front moving northwest to southeast. As this occurs, background surface winds will become light and veer southeasterly, allowing for daytime sea breezes and nighttime land breezes ahead of its arrival. There's still a fair bit of uncertainty with regards to the timing of the front, as the ECWMF displays a much earlier arrival time compared to the GFS. Furthermore, ECMWF shows the front to have a more modest impact to the Hawaiian Islands, dissipating apart much quicker. GFS, on the other hand, supports the likeliness of enhanced shower activity as it passes through. Further analysis will be needed to determine which scenario proves more favorable in the forecast guidance over the coming days.

Aviation

Light to moderate trades will persist throughout the day and will bring periods of showers to windward and mauka areas. A band of moisture east of the islands will also move westward through the early portion of today, bringing enhanced showers, mainly across windward areas, but may trickle into the leeward and interior portions of the state. Brief MVFR conditions remain possible with passing showers. Otherwise VFR conditions prevail.
AIRMET Tango remains in effect for moderate turbulence between FL290-FL360 extending from Kauai to Maui.

Marine

A surface high pressure ridge will remain north of the Hawaii region, winds flowing around this ridge will produce gentle to moderate easterly winds today, then decreasing and veering more southeasterly to southerly from Tuesday to Wednesday as another cold front moves into the region from the northwest. A consensus of weather model guidance suggests this cold front may move into the western Hawaiian islands from late Wednesday into Thursday, then diminishing by Friday.
The current medium period north-northwest (340-350 degree) swell continues to slowly fade into Monday, bringing surf back down to below average levels for this time of year. The next two long to medium period overlapping northwest (310-320 degree) swell pulses will arrive on Monday and Tuesday, boosting surf along north and west facing shores and possibly reaching marginal advisory levels by Wednesday.
Choppy east shore surf will remain small and decline for the next few days as trades gradually ease. Expect minimal background energy for south facing shores keeping south shore surf heights above flat levels.
Peak monthly tides combined with water levels that are running higher than predicted will likely lead to minor flooding along the shoreline and in low-lying coastal areas. Coastal flooding is possible through the peak high tide this morning.

Fire weather

Light to moderate trades and relative humidity values in the low- to mid-50s will maintain below critical fire weather thresholds through much of this week. Winds are expected to ease further as the week progresses preceding a wetter weather pattern during the latter half of the week. The morning temperature inversion heights sloped from around 6500 feet at Lihue to around 10000 feet over Hilo.

HFO Watches/Warnings/Advisories

None.

Data Courtesy of NOAA.gov