Hilo

Tonight: Mostly cloudy. Scattered showers and isolated thunderstorms in the evening, then scattered showers after midnight. Haze through the night. Lows 60 to 67 near the shore to 48 to 55 at 4000 feet. Northeast winds up to 10 mph shifting to the west after midnight. Chance of rain 50 percent.

Sunday: Partly sunny with scattered showers. Highs around 79 near the shore to 63 to 68 at 4000 feet. East winds up to 10 mph. Chance of rain 50 percent.

Sunday Night: Mostly cloudy. Numerous showers in the evening, then scattered showers after midnight. Lows 59 to 67 near the shore to 47 to 55 at 4000 feet. Light winds. Chance of rain 70 percent.

Kona

Tonight: Partly cloudy with isolated showers. Haze. Lows around 70 near the shore to 43 to 49 near 5000 feet. Light winds. Chance of rain 20 percent.

Sunday: Sunny in the morning, then partly sunny with scattered showers in the afternoon. Haze through the day. Highs around 83 near the shore to around 66 near 5000 feet. Light winds. Chance of rain 30 percent.

Sunday Night: Mostly cloudy with scattered showers in the evening, then partly cloudy with isolated showers after midnight. Haze through the night. Lows around 70 near the shore to 43 to 49 near 5000 feet. Light winds. Chance of rain 50 percent.

Waimea

Tonight: Mostly cloudy with scattered showers. Haze. Lows 60 to 69 near the shore to 52 to 59 near 3000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Sunday: Partly sunny with scattered showers. Haze. Highs around 77 near the shore to 68 to 76 near 3000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Sunday Night: Mostly cloudy. Numerous showers in the evening, then scattered showers after midnight. Haze through the night. Lows 59 to 68 near the shore to 52 to 59 near 3000 feet. East winds up to 10 mph. Chance of rain 70 percent.

Kohala

Tonight: Mostly cloudy with scattered showers. Haze. Lows 60 to 69 near the shore to 52 to 59 near 3000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Sunday: Partly sunny with scattered showers. Haze. Highs around 77 near the shore to 68 to 76 near 3000 feet. East winds up to 15 mph. Chance of rain 50 percent.

Sunday Night: Mostly cloudy. Numerous showers in the evening, then scattered showers after midnight. Haze through the night. Lows 59 to 68 near the shore to 52 to 59 near 3000 feet. East winds up to 10 mph. Chance of rain 70 percent.

South Big Island

Tonight: Partly cloudy. Breezy. Isolated showers in the evening. Haze through the night. Lows around 71 near the shore to around 50 near 5000 feet. East winds up to 20 mph shifting to the northeast 10 to 15 mph after midnight. Chance of rain 20 percent.

Sunday: Sunny and breezy. Haze through the day. Isolated showers in the afternoon. Highs around 83 near the shore to around 65 near 5000 feet. East winds 10 to 20 mph decreasing to up to 20 mph in the afternoon. Chance of rain 20 percent.

Sunday Night: Partly cloudy with isolated showers. Haze. Lows around 70 near the shore to around 50 near 5000 feet. Northeast winds up to 10 mph. Chance of rain 20 percent.

Puna

Tonight: Mostly cloudy. Scattered showers and isolated thunderstorms in the evening, then scattered showers after midnight. Haze through the night. Lows 60 to 67 near the shore to 48 to 55 at 4000 feet. Northeast winds up to 10 mph shifting to the west after midnight. Chance of rain 50 percent.

Sunday: Partly sunny with scattered showers. Highs around 79 near the shore to 63 to 68 at 4000 feet. East winds up to 10 mph. Chance of rain 50 percent.

Sunday Night: Mostly cloudy. Numerous showers in the evening, then scattered showers after midnight. Lows 59 to 67 near the shore to 47 to 55 at 4000 feet. Light winds. Chance of rain 70 percent.

Waikoloa

Tonight: Partly cloudy with isolated showers. Haze through the night. Lows around 70 near the shore to 47 to 52 above 4000 feet. Northeast winds up to 10 mph in the evening becoming light. Chance of rain 20 percent.

Sunday: Sunny. Haze through the day. Isolated showers in the afternoon. Highs 81 to 86 near the shore to 64 to 70 above 4000 feet. Light winds. Chance of rain 20 percent.

Sunday Night: Partly cloudy with isolated showers. Haze. Lows 67 to 72 near the shore to 47 to 52 above 4000 feet. Light winds. Chance of rain 20 percent.

Detailed Forecast

Synopsis

Gentle to occasionally breezy trade winds have returned and will anchor in place through the middle of next week. A more active weather pattern across the Pacific as a series of troughs pass east across the region and increase the odds of a more wet end of January. Higher moisture within these trades will enhance mainly windward area and mauka slope showers, with infrequent short-lived leeward shower activity, through Tuesday. A frontal passage early Monday will reinforce northerly winds in its wake while producing scattered showers along and ahead of it. A more significant change in the pattern will occur later next week when troughing north and west of the region travels across the islands. This scenario will likely increase areal precipitation coverage while strengthening southerly winds.

Discussion

A lingering persistent low level trough across the eastern waters has been the focus for early day showers and isolated thunderstorms over and off Big Island's Hilo and Puna regions…that then transitioned to strong thunderstorms rooting themselves on both volcanoes' eastern slopes. Upper level dynamics may have played a small role in storm development and regeneration as the divergent left front quadrant of the southern leg of a splitting jet to our west moved over the lower level boundary. A tale of two cities this maximum temperature-wise today as overcast, showery Hilo remained in the 70s while Honolulu warmed to 86 F (tied the max T record from 1981) under gentle trades.
Sunday's highest probabilities for the regeneration of showers will be further up the chain as the remnants of today's eastern convergence zone treks northwestward toward the western half of the state. An approaching cold front associated with low pressure far north of the Hawaiian Islands is pulling a southern band of rich moist air up and over the eastern half of the state. The highest chances for more frequent periods of rain, with another round of afternoon thunderstorms just north of the islands, will be centered around windward Oahu and Kauai Sunday. Due to slow cell movement, a quick 1 to 2 inches of rain over a short amount of time is not out of the question. Higher mid layer moisture will stick in place downstream of the approaching shallow cold front Sunday into Monday. As the low way up north is absorbed by a larger scale trough, the central or eastern water low level boundary will fizz out and merge with Monday's front as it progressively passes southeast across Kauai. Breezy northerlies will fill in the front's wake through Monday. Shower activity will favor northern and eastern exposures of each island through the Monday through Tuesday frontal passage.
The front will diminish into a trough and likely stall near Big Island and Maui late Tuesday into Wednesday. This boundary will then slowly lift northward as more unstable southerly flow begins to develop by late Wednesday. The extended NWP guidance has been consistent in holding onto the solution of a developing mid to upper trough within a northwest flow pattern going into the middle of next week. As this trough deepens and moves into the islands, this will favor lower pressures evolving in the close proximity of Hawaii. While there have been run-to-run differences in NWP model guidance, the signal is that a cut-off low will develop over or just north of the state. A majority of the ensemble members are also latching onto a passing low/open wave trough progressively passing north northeast of the island chain Thursday into Friday. The specific impacts of this low's (or trough's) potential development and evolution will be unknown until the event begins to unfold (as early as) Wednesday. Thus, it is best to keep any speculation about Day 5 and 6's weather pattern change at bay until NWP probabilities have a better handle on the dynamics. The most logical bet will be on a more seasonal (winter-like) wet pattern with gustier winds to end January. Southwesterlies along Big Island summits may become very strong Thursday and Friday. There may also be a rain-snow mix or snow showers over the highest elevations during the strongest winds.

Aviation

Light to moderate trade winds will steer low clouds and limited showers to windward areas of the islands. Heavy showers and thunderstorms over the Big Island and Maui and adjacent waters should continue to diminish overnight as an upper trough shifts E, and weak ridging briefly builds over the area. End result should be ISOL MVFR VIS/CIG in SHRA through early Sunday. A sharpening low-level trough over the island chain will combine with a new trough aloft to bring the potential for increased windward showers on Kauai and Oahu by later Sunday.

Marine

Light to moderate northeast to east winds will persist through the rest of the weekend as a weak surface ridge lifts north of the state. Pockets of fresh breezes may develop over the typically windier waters and channels from Maui County to the Big Island during this time. Moderate to fresh north to northeast winds are expected to return over the western half of the state late Sunday through Monday, then extend statewide from Tuesday through Wednesday as another front moves into the area. It is also possible that Small Craft Advisory seas may briefly occur across Kauai waters on Sunday night.
Surf along shores exposed to the mixed north and north northwesterly swells has continued to ease today. Wave heights at offshore and nearshore buoys to the north confirm that the swells are fading. North shore surf will continue this trend tonight, dipping below average from Sunday through Monday.
With a blocking high persisting over the northwest Pacific, the primary swell source will remain out of the north next week, featuring a mix of short-period wind waves associated with the northerly winds expected locally and medium-period northerly swells. Forecast guidance indicates an upward trend in surf beginning Tuesday and continuing into late next week due to a potential gale forming well to the north. It is possible that surf heights could approach advisory levels around mid-week if this scenario evolves.
Surf along east-facing shores not exposed to northerly swells will remain small each day due to the lack of strong trades locally and upstream. Surf along south-facing shores will remain around the seasonal average, with mainly a mix of short-period southeast and an occasional background south swell moving through.

Fire weather

Afternoon RH values have rebounded back into the 50 and 60 percentiles today. Higher moisture will be moving across the islands the next few days. Sustained interior winds are expected to remain under RFW thresholds the next several days. A more wet pattern is expected through next week. Thus, critical fire behavior is not anticipated the next several days.

HFO Watches/Warnings/Advisories

None.

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Data Courtesy of NOAA.gov