| Current Conditions | ||
| Temp |  | -0.9 C |
| RH | | 45 % |
| Wind | | NNE 0 mph |
| Road | | Open (4x4) |
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Hawaiian Islands Synoptic Discussion and Guidance 572 FXHW60 PHFO 231317 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 317 AM HST Fri Apr 23 2021 .SYNOPSIS... Moderate to breezy easterly trade winds will persist through the weekend, with clouds and showers favoring windward and mountain locations. Windward shower coverage could increase later today through Saturday night as an upper low moves through from north to south. Warm and humid conditions, along with increasing rainfall chances, may return early next week as the trade winds diminish ahead of an approaching front. && .DISCUSSION... The surface trough northwest of Kauai that disrupted the trade winds earlier in the week will continue retreating westward and away from the area today. Easterly trade winds have returned, and will likely become breezy over the weekend as high pressure builds to the north. Windward showers may increase later today through Saturday night as an upper low drops southward into the area. Some showers could reach leeward locations as the inversion weakens and the trades increase - especially through the overnight and early morning hours. In addition to the increasing shower coverage, a thunderstorm or two can't be ruled out over the Big Island slopes through the afternoon hours today and Saturday. Models show the upper low briefly drifting south of the state Sunday through Sunday night, then lifting back through the area and merging with an upper trough passing to the north Monday through Tuesday. The subtropical ridge will weaken once again as a front approaches the region from the northwest. If this scenario evolves, a land and sea breeze regime, along with warm and humid conditions, will return and continue through the first half of next week. Rainfall chances will trend up through this time, with the best coverage setting up over interior and leeward locations through the afternoon hours. && .AVIATION... A high pressure ridge north of the Hawaiian Islands will maintain moderate trade winds today and tonight. Periods of mountain obscurations are possible for windward slopes, especially over the eastern slopes of Maui and the Big Island as cloud bands drift through the region. An upper level low north of the island chain will drift south across the state through Saturday. Instability with this upper low will likely enhance shower activity mainly over windward and mountain locations. No AIRMETs are in effect. However mountain obscurations may be needed for windward Big Island later this morning. && .MARINE... A surface high passing north of the islands today will maintain fresh to locally strong trade winds through the weekend. A small craft advisory is in effect to until 6 am HST Sunday for the windier waters of Maui County and waters south of the Big Island. Trade winds are expected to trend down and become southeast on Monday, ahead of an approaching front from the northwest. A northwest swell has peaked and will be subsiding slowly through Saturday. A small west-northwest swell is tabbed to arrive late Monday, peak Tuesday, then subside gradually through Wednesday. The source of this swell is from a long lived distant typhoon. A small short period northwest pulse is slated to arrive Wednesday night and Thursday. Small surf will continue along the south facing shores into next week due to a series of long period swell from the southern hemisphere. The boost in the trade winds will raise the surf into the small to moderate range along the east facing shores into the weekend. The surf will trend smaller after Sunday as the trade wind diminishes. && .HFO WATCHES/WARNINGS/ADVISORIES... Small Craft Advisory until 6 AM HST Sunday for Maalaea Bay- Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters-Big Island Southeast Waters. && $$ DISCUSSION...Gibbs AVIATION...Bohlin MARINE...H Lau Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office |
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