Area Forecast Discussion
Issued by NWS Honolulu, HI
Issued by NWS Honolulu, HI
993 FXHW60 PHFO 271942 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 942 AM HST Thu Jun 27 2024 .SYNOPSIS... Stable conditions and breezy to locally windy trade winds will continue today. Light showers will generally focus along windward and mauka areas. An upper level low will approach the islands on Friday and pass north of the state this weekend. This will destabilize the island atmosphere, increasing shower activity and introducing isolated thunderstorm chances for portions of the region. && .DISCUSSION... Breezy to locally strong easterly trade winds continue to prevail across the islands today as high pressure remains centered far north-northeast of the state. Latest radar and satellite imagery this morning shows mostly dry conditions, though a few light showers are continuing to move into windward and mauka areas. Rainfall amounts have been relatively light, with windward and central Oahu receiving the most rainfall this morning. For the rest of today, expect continued breezy to locally strong trades with isolated to scattered light showers favoring windward and mountain locations. Leeward areas will remain mostly dry, with the exception of the Kona slopes of the Big Island where afternoon cloud buildups and a few showers will be possible. The high pressure to our north will subtly weaken tonight, which will relax the local pressure gradient a bit, easing winds for Friday into the weekend. Impulses of moisture embedded in the trade wind flow will continue to favor windward and mauka areas, though rainfall accumulation will be limited for most locations through Friday. However, guidance remains consistent that a low aloft will approach the region from the east beginning on Friday. This will begin to destabilize the island atmosphere. It is possible that isolated thunderstorms could develop over the Big Island slopes Friday afternoon, fueled by daytime heating, topographic effects, and an increasingly unstable environment. The low aloft will continue moving towards the main Hawaiian Islands this weekend, enhancing trade wind showers and introducing the possibility of isolated thunderstorms across the far western end of the state closer to the low. Additionally, isolated thunderstorms will be possible again on Saturday afternoon for the Big Island slopes. As previous discussions have mentioned, however, precipitable water values will hover near or slightly above normal (1.3 inches), so moisture availability will be a limiting factor and may prevent enhanced trade wind showers and isolated thunderstorms from being fully realized. A few updates have been made to the forecast for Friday though Sunday with this morning`s updates, but the overall philosophy remains unchanged. Conditions will return to a more typical summertime trade wind pattern by early next week as the low aloft moves away from the state and weakens. High pressure will become re-established north of the islands, resulting in locally breezy trades returning to the state. && .AVIATION... Breezy trades will persist across the island chain today. SHRA and low cigs could bring brief periods of MVFR conds over windward and mauka locations. Otherwise, VFR conds should prevail. No AIRMETs are in effect at this time. However, AIRMET Sierra for mtn obsc may be needed later if SHRA coverage increases. && .MARINE... High pressure will dominate the central North Pacific through the weekend and will strengthen even further early next week. A Small Craft Advisory (SCA) remains in effect for the typically windy waters around Maui and the Big Island through 6 PM this evening, and may be needed through the weekend as channeled winds flirt with SCA levels. Trade winds will increase to fresh to strong levels early next week. A series of south swells will keep south shore surf near the summertime average through the weekend. Surf will drop below normal levels for much of next week. The current small northwest swell will keep north shore surf slightly elevated through tomorrow, then fade out over the weekend. Typical mostly flat summertime conditions will prevail along north facing shores next week. East shore surf will remain well below normal through the weekend, then trend closer to seasonal levels next week as the trades strengthen over and upstream of the islands. && .HFO WATCHES/WARNINGS/ADVISORIES... Small Craft Advisory until 6 PM HST this evening for Maalaea Bay- Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters. && $$ DISCUSSION...Vaughan AVIATION...Walsh MARINE...TS/ASB