Photo Credit: James Grenz

Hilo

Today: Mostly sunny with isolated showers. Highs around 80 near the shore to 64 to 70 at 4000 feet. South winds up to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows 60 to 67 near the shore to 52 to 57 at 4000 feet. Southwest winds up to 10 mph. Chance of rain 40 percent.

Sunday: Cloudy. Haze in the morning. Numerous showers in the morning, then scattered showers in the afternoon. Highs around 79 near the shore to 64 to 70 at 4000 feet. Southwest winds up to 10 mph shifting to the east in the afternoon. Gusts up to 30 mph. Chance of rain 70 percent.

Kona

Today: Mostly sunny. Isolated showers in the afternoon. Highs 78 to 84 near the shore to around 66 near 5000 feet. Light winds. Chance of rain 20 percent.

Tonight: Mostly clear. Lows 65 to 71 near the shore to 45 to 52 near 5000 feet. Light winds.

Sunday: Mostly sunny in the morning, then mostly cloudy with scattered showers in the afternoon. Haze through the day. Highs 78 to 84 near the shore to around 67 near 5000 feet. Light winds. Chance of rain 40 percent.

Waimea

Today: Mostly sunny. Isolated showers in the afternoon. Highs around 78 near the shore to 68 to 77 near 3000 feet. Light winds becoming northeast up to 10 mph in the afternoon. Chance of rain 20 percent.

Tonight: Mostly clear. Lows 60 to 69 near the shore to 50 to 59 near 3000 feet. Southeast winds up to 10 mph in the evening becoming light.

Sunday: Mostly cloudy. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Haze through the day. Highs around 78 near the shore to 69 to 77 near 3000 feet. Northeast winds up to 20 mph. Chance of rain 70 percent.

Kohala

Today: Mostly sunny. Isolated showers in the afternoon. Highs around 78 near the shore to 68 to 77 near 3000 feet. Light winds becoming northeast up to 10 mph in the afternoon. Chance of rain 20 percent.

Tonight: Mostly clear. Lows 60 to 69 near the shore to 50 to 59 near 3000 feet. Southeast winds up to 10 mph in the evening becoming light.

Sunday: Mostly cloudy. Breezy. Numerous showers in the morning, then scattered showers in the afternoon. Haze through the day. Highs around 78 near the shore to 69 to 77 near 3000 feet. Northeast winds up to 20 mph. Chance of rain 70 percent.

South Big Island

Today: Breezy. Mostly sunny with isolated showers. Highs around 79 near the shore to around 66 near 5000 feet. East winds up to 20 mph. Chance of rain 20 percent.

Tonight: Mostly clear. Breezy. Lows around 70 near the shore to around 50 near 5000 feet. Northeast winds up to 15 mph increasing to 10 to 20 mph after midnight.

Sunday: Breezy. Mostly sunny in the morning, then partly sunny with isolated showers in the afternoon. Haze through the day. Highs around 80 near the shore to around 68 near 5000 feet. East winds 10 to 20 mph. Chance of rain 20 percent.

Puna

Today: Mostly sunny with isolated showers. Highs around 80 near the shore to 64 to 70 at 4000 feet. South winds up to 15 mph. Chance of rain 20 percent.

Tonight: Partly cloudy. Isolated showers in the evening, then scattered showers after midnight. Lows 60 to 67 near the shore to 52 to 57 at 4000 feet. Southwest winds up to 10 mph. Chance of rain 40 percent.

Sunday: Cloudy. Haze in the morning. Numerous showers in the morning, then scattered showers in the afternoon. Highs around 79 near the shore to 64 to 70 at 4000 feet. Southwest winds up to 10 mph shifting to the east in the afternoon. Gusts up to 30 mph. Chance of rain 70 percent.

Waikoloa

Today: Mostly sunny. Isolated showers in the afternoon. Highs around 81 near the shore to around 67 above 4000 feet. Southeast winds up to 10 mph shifting to the northwest in the afternoon. Chance of rain 20 percent.

Tonight: Mostly clear. Lows 66 to 71 near the shore to 45 to 54 above 4000 feet. Light winds becoming southeast up to 10 mph after midnight.

Sunday: Sunny in the morning then becoming partly sunny. Haze. Highs 78 to 83 near the shore to around 67 above 4000 feet. East winds up to 10 mph shifting to the northwest in the afternoon.

Detailed Forecast

Synopsis

A front will stall northwest of Kauai today and maintain unsettled weather, mainly across the western portions of the state. The atmosphere will trend more stable on Sunday and Monday as trade winds return. Another front will approach the area from the northwest by the middle of next week.

Discussion

Radar this morning shows a band of showers with enhanced rainfall rates streaming northward across the western end of the state and Kauai. The showers are the result of convergent flow tightening in advance of an approaching cold front, which is currently around 150 miles northwest of Kauai. Lightning data this morning shows lightning remaining well northwest of the state in closer proximity of the front.
Today…abundant moisture and modest instability will linger across the western and central portions of the state. The sounding data from Lihue (12z Sat) showed cape values near 700 j/kg with PW values around 1.75″. PW values are forecast to continue slowly increasing today as the front approaches from the northwest. This increase in PW values is supported by satellite based imagery showing PWs over 1.85″ approaching the western end of the state. The latest trends show this moist and unstable airmass expanding eastward across Oahu today. Radar and satellite this morning are already showing showers increasing south of Oahu. This airmass will continue the threat of locally heavy rainfall and potential flooding impacts today in the vicinity of Kauai and Oahu. Thunderstorm probabilities remain extremely limited, as best instability lingers north of the state. Shower chances will decrease across the island chain early Sunday, as the front weakens and exits northeast.
Sunday through next week…MSI values (less than 2) show a more stable pattern redeveloping over the state Sunday through Tuesday. A trade wind weather pattern becomes reestablished across the region Sunday into early next week, with moderate trades focusing showers to mainly windward areas. Models are becoming in better agreement with another cold front, with an assoicated band of moisture and increasing instability, advancing over the western end of the state Wednesday. However, models differ drastically Thursday into next weekend with placement and movement of surface and upper level features.

Aviation

Early this morning, a band of showers is streaming over Kauai and its adjacent waters. This band of showers is supported by low- level convergence ahead of a front approaching the islands from the west. Moderate to locally breezy southerly winds are prevailing from Kauai to Oahu this morning, though a surface ridge near Maui and the Big Island is keeping southeasterly winds lighter for the eastern end of the state.
Showers and low clouds will continue across Kauai today, and possibly reach Oahu, as the front stalls northwest of Kauai. Widespread MVFR ceilings and visibilities are likely on Kauai with occasional IFR in heavier showers. Elsewhere, VFR conditions are expected to prevail under drier conditions.
AIRMET Sierra remains in effect for tempo mountain obscuration above 2,000 feet for Kauai this morning. This AIRMET is likely to remain in effect through today. Additionally, AIRMET Tango remains in effect for moderate low-level turbulence to the north of Kauai's terrain due to the gusty southerly winds, though this may be cancelled later this morning. AIRMET Tango is also posted statewide for moderate turbulence aloft and is likely to remain in effect through at least early afternoon.

Marine

Moderate southerly winds across the nearshore waters for those waters surrounding Kauai will become variable as a weakening front stalls over those waters today. Elsewhere, moderate southeasterly breezes will prevail over the waters from Oahu eastward. Relatively weak winds will occur through early next week with more moderate to fresh winds blowing through the notoriously windier bays and channels surrounding Maui and Big Island Tuesday on through mid week. A large northwest swell will arrive tonight and move around the islands through Sunday. A Small Craft Advisory will be in effect from Midnight Sunday through Monday to account for combined 15 to 20 foot seas.
An extra large, long period northwest (310-320 degree) swell will arrive and travel around the islands tonight through Sunday. This XL swell will produce giant-size surf along north and west-facing shores as it reaches its peak Sunday. Adverse impacts to coastal properties, harbors, and infrastructure (including coastal roadways) such as overwash is expected, particularly as this falls in line with Sunday morning's highest high tides of the month. A High Surf Warning (HSW) will be in effect from midnight Sunday through early Monday morning for the north and west-facing shores of Niihau, Kauai, Oahu and Molokai as well as the north-facing shores of Maui. Timing of the onset of warning level surf and the duration of the event will be somewhat variable and all dependent upon the timing of the swell's arrival (e.g., forerunners). Due to timing and a more westerly component of the swell, surf will likely reach HSW criteria along the north and west-facing shores of Big Island late Sunday with similar overwash complications due to this swell coinciding with the Sunday's high tides. The swell will gradually subside from Sunday night into early next week, falling below HSW thresholds sometime on Monday.
Another long period, large to extra large northwest (310-320 degree) swell may bring another round of warning level surf to the islands by the middle of next week. South swell remains at very low, background levels through Saturday with a chance for a slight boost to south-facing shore surf later this weekend. Meanwhile, short period east chop associated with returning trades will produce elevated surf along east-facing shores Sunday into early next week.

HFO Watches/Warnings/Advisories

High Surf Warning from midnight tonight to 6 AM HST Monday for Niihau, Waianae Coast, Oahu North Shore, Maui Windward West, Kauai North, Molokai Windward, Molokai North, Molokai West, Maui Central Valley North, Windward Haleakala.
Small Craft Advisory from midnight tonight to 6 PM HST Monday for Kauai Northwest Waters, Kauai Windward Waters, Kauai Leeward Waters, Kauai Channel, Oahu Windward Waters, Oahu Leeward Waters, Kaiwi Channel, Maui County Windward Waters, Alenuihaha Channel, Big Island Windward Waters, Big Island Leeward Waters, Big Island Southeast Waters.

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Data Courtesy of NOAA.gov