Area Forecast Discussion
Issued by NWS Honolulu, HI
Issued by NWS Honolulu, HI
958 FXHW60 PHFO 010111 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 311 PM HST Tue Apr 30 2024 .SYNOPSIS... Moderate east to east-southeasterly winds will gradually build on Wednesday. Limited showers will be focused over windward areas, while afternoon clouds and a few showers form over sheltered leeward terrain in the afternoon. Trade winds will strengthen on Thursday and will become breezy and gusty Friday through early next week. Rainfall will favor typical windward slopes, with an increase in showers possible late this weekend through Monday as a disturbance aloft passes overhead. && .DISCUSSION... Hawaii remains under a stable east to east-southeasterly trade wind flow, as a weak trough about 300 miles northwest of Kauai bisects a pair of high pressure cells to the distant northeast and northwest. There are no organized areas of moisture moving along this flow, and mid-level ridge is maintaining stable conditions with an inversion near 6,000 ft. As a result, rainfall along windward slopes has been modest today, less than a tenth of an inch at most gages, and while sea breezes have produced low clouds over sheltered leeward terrain, the only island that has experienced much leeward rainfall this afternoon is Kauai. Expect leeward clouds and isolated showers to largely dissipate early this evening, with continued modest rainfall over windward slopes. Trade winds will gradually strengthen and become more easterly Wednesday and Thursday, as the trough to the northwest fills and surface high pressure consolidates to the north. Winds will likely be weak enough for some leeward sea breezes Wednesday afternoon, but aside from typical showers on the South Kona slopes of the Big Island, chances for leeward rainfall will be minimal. Continued westerly flow aloft may bring some patches of thin high clouds. A 1030 mb surface high will settle far north of the state late Thursday and Friday, driving breezy and gusty trade winds and mainly windward rainfall into early next week. A compact upper- level low lingering west of the state Thursday and Friday will eventually move overhead during the weekend. Confidence in a significant boost in shower activity is not high at this time, though the highest chances for enhanced shower activity looks to be on Sunday and Monday. && .AVIATION... Hawaii remains wedged between surface high pressure far northeast of the state and a trough to the west. This pattern will maintain light to moderate east to east-southeasterly flow into Wednesday. Expect scattered showers along the windward portions of the islands, most active at night and early morning, and isolated showers elsewhere. Brief periods of MVFR ceilings and visibility may occur with this activity, though not expecting anything widespread. Sea breezes will give way to land breezes for most leeward areas again tonight, clearing out the afternoon clouds. Sea breezes may still occur for some leeward areas Wednesday afternoon, as the background flow begins to shift back out of an easterly trade wind direction. No AIRMETs are currently in effect, nor expected through the afternoon. && .MARINE... High pressure far northeast of the state will strengthen and expand through the remainder of the week. A weak trough to the northwest of the state will dissipate Thursday. In response, moderate to locally strong east-southeast trade winds this afternoon will shift to become more easterly by Friday. A Small Craft Advisory (SCA) is now in effect for typical windy waters around the Big Island and Maui. This advisory will likely be expanded to include additional waters on Thursday and Friday. Tiny surf will persist along north facing shores through Friday, with a small pulse of northwest swell swell expected this weekend. A small long period south swell will linger into Wednesday. The next small long period south swell will arrive this weekend. Rough east shore surf will likely return on Friday, rising above seasonal averages for the weekend. && .HFO WATCHES/WARNINGS/ADVISORIES... Small Craft Advisory until 6 PM HST Thursday for Pailolo Channel- Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters. && $$ DISCUSSION...Wroe AVIATION...TS MARINE...Bedal/Vaughan