West Side

Today: Mostly sunny. Isolated showers in the morning. Highs 81 to 86. East winds up to 15 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy. Isolated showers in the evening. Lows 69 to 77. East winds up to 15 mph. Chance of rain 20 percent.

Friday: Partly sunny in the morning then becoming mostly sunny. Highs around 85. East winds up to 15 mph.

South Side

Today: Mostly sunny in the morning then becoming partly sunny. Highs around 89. North winds up to 15 mph increasing to 10 to 15 mph in the afternoon.

Tonight: Mostly cloudy. Lows 71 to 77. North winds up to 15 mph.

Friday: Partly sunny in the morning then becoming mostly sunny. Highs around 90. North winds up to 15 mph.

North Shore

Today: Partly sunny with isolated showers. Highs 80 to 87 near the shore to around 69 near 5000 feet. East winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 20 percent.

Tonight: Mostly cloudy with isolated showers. Lows around 73 near the shore to around 54 near 5000 feet. Southeast winds 10 to 15 mph. Chance of rain 20 percent.

Friday: Breezy. Partly sunny with isolated showers. Highs 81 to 87 near the shore to around 70 near 5000 feet. East winds 10 to 20 mph. Chance of rain 20 percent.

Central Maui

Today: Mostly sunny in the morning then becoming partly sunny. Highs 82 to 89. Northeast winds 10 to 15 mph.

Tonight: Mostly cloudy. Lows around 72. Northeast winds up to 15 mph.

Friday: Partly sunny in the morning then becoming mostly sunny. Breezy. Highs 84 to 91. Northeast winds up to 20 mph shifting to the east 10 to 20 mph in the afternoon.

Upcountry

Today: Mostly cloudy with isolated showers. Highs around 66 at the visitor center to around 69 at the summit. East winds up to 10 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy. Isolated showers in the evening. Lows around 51 at the visitor center to around 49 at the summit. East winds up to 10 mph. Chance of rain 20 percent.

Friday: Partly sunny. Isolated showers in the morning. Highs around 68 at the visitor center to around 71 at the summit. East winds up to 15 mph. Chance of rain 20 percent.

East Maui

Today: Partly sunny with isolated showers. Highs 80 to 87 near the shore to around 69 near 5000 feet. East winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 20 percent.

Tonight: Mostly cloudy with isolated showers. Lows around 73 near the shore to around 54 near 5000 feet. Southeast winds 10 to 15 mph. Chance of rain 20 percent.

Friday: Breezy. Partly sunny with isolated showers. Highs 81 to 87 near the shore to around 70 near 5000 feet. East winds 10 to 20 mph. Chance of rain 20 percent.

Lanai City

Today: Mostly sunny. Isolated showers in the afternoon. Highs 75 to 83. Northeast winds 10 to 15 mph. Chance of rain 20 percent.

Tonight: Mostly cloudy with isolated showers. Lows around 68. Northeast winds up to 10 mph in the evening becoming light. Chance of rain 20 percent.

Friday: Partly sunny. Highs 76 to 84. Northeast winds up to 10 mph.

Kaunakakai

Today: Mostly sunny with isolated showers. Highs 75 to 90. Northeast winds up to 15 mph increasing to 10 to 15 mph in the afternoon. Chance of rain 20 percent.

Tonight: Partly cloudy. Lows 62 to 75. East winds around 10 mph.

Friday: Mostly sunny in the morning then becoming partly sunny. Highs 76 to 91. East winds 10 to 15 mph.

Detailed Forecast

Synopsis

A low level trough will move through the region today, weakening the trades and increasing clouds and showers through Friday morning. High pressure will build back in across the region from Friday into early Sunday, bringing a return to moderate to locally breezy trade winds. Another brief increase in clouds, showers and humidity levels will develop from Sunday afternoon through Monday as another low level trough moves westward through the islands; this system is associated with the remnants of former tropical cyclone Ivo. Stable drying trends return from Tuesday onward.

Discussion

Water vapor imagery early this morning shows a weak elongated trough stretching southwest to northeast across the island chain. A combination of local radar and infra-red satellite imagery shows scattered showers moving into the islands with the trades, favoring windward areas. Some isolated showers have drifted over the leeward terrain on the smaller islands. However, overnight rainfall totals are generally unimpressive, less than 0.05 of an inch.
A low level trough will move through the islands from west to east today. The passage of this trough will help weaken trades and transition us into a hybrid sea breeze pattern. In addition, this subtle feature will act to deepen the inversion heights into the 7,000 to 8,000 foot range and bring a slight uptick in showers along windward locations this morning with additional diurnal driven development over leeward terrain by this afternoon. Model derived Showalter index depicts enough instability to add isolated thunderstorms to interior portions of the Big Island later this afternoon.
By Friday, a surface ridge will build north of the Hawaiian Islands, allowing moderate to locally breezy trades to return. Drier air will filter in from the east as a very stable upper level ridge nudges its way back over the state. As inversion heights lower, cloud cover and shower activity will wane with only isolated windward showers expected through Sunday morning.
By Sunday afternoon, yet another disturbance will move from east to west through the islands. This trough will have slightly different island by island impacts as deeper moisture and dynamics are associated with the remnants of former tropical cyclone Ivo that formed and diminished in the Eastern Pacific basin. This trough will increase humidity levels across the state from Sunday afternoon through Monday. Temperature inversion heights will lift to around 8,000 to 9.000 feet elevation, enhancing clouds and showers in a moderate trade wind weather pattern. Our confidence in this brief period of enhanced shower activity is only fair at this time. Typically these remnant tropical systems tend to be compact in size and may possibly track a bit further north than currently predicted by our global weather models. If this system does move further north of track, then our current weather forecast will change, resulting in less clouds and showers reaching the Hawaiian Islands. Stay tuned.
A high pressure ridge will swiftly build back into the region on Tuesday, just as the remnant trough continues on its westward journey away from the state. This returning ridge will bring strong stable trends with drier humidity levels, and a return to more typical dry summer weather across the state through the middle of next week.

Aviation

Cloud and shower trends will increase from east to west across the islands today as a weak disturbance drifts westward down the island chain. Mostly VFR conditions will prevail, with brief periods of MVFR conditions possible in passing showers.
No AIRMETs in effect.

Marine

Surface trough moving westward north of the waters will keep light to locally moderate flow through the day. Trade winds will gradually strengthen Friday into the weekend as the high builds north of the state. A Small Craft Advisory for the windier waters and channels around Maui County and the Big Island could start as early as Friday morning and hold through the weekend.
Surf along south facing shores will remain small through tonight with mainly background medium to long period energy. Surf should see a slight bump early Friday and hold through early next week as a series of small long period southerly energy fills in.
A small, medium period northeast swell has filled in and will keep surf along east facing shores elevated through the weekend. As this swell declines, the short period energy will fill in as trade winds increase into the weekend. North facing shores will remain flat to tiny through the forecast period except for areas that may be exposed to the small northeast swell.

Fire weather

Weather conditions will likely remain below critical fire weather thresholds into early next week. A low level disturbance will move into the region today through Friday morning producing a slight increase in clouds and showers. Another low level disturbance associated with the remnants of former tropical cyclone Ivo will likely increase humidity levels and shower trends on Sunday and Monday. A return to lower humidity levels will develop by Tuesday as a stable upper level ridge builds back over the island chain.

HFO Watches/Warnings/Advisories

None.

Data Courtesy of NOAA.gov