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Area Forecast Discussion
Issued by NWS Honolulu, HI
Issued by NWS Honolulu, HI
000 FXHW60 PHFO 141952 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 952 AM HST Sun Apr 14 2024 .SYNOPSIS... The potential for heavy rainfall and thunderstorms associated with a front will continue through Monday, initially over the western end of the state through tonight, then over the eastern end on Monday. Conditions will gradually improve from west to east through the first half of the week as high pressure builds to the north in the wake of the front. Breezy southerly winds ahead of the front will hold today, then ease into the light to moderate range as they shift to the north, then to a more typical trade wind direction around midweek. Expect a more typical trade wind pattern to return with showers favoring windward and mauka locations through the second half of the week. && .DISCUSSION... The frontal boundary remains just west and northwest of Kauai this morning with moist southerly winds ahead of the front. Showers have been increasing all morning over Kauai and we do expect the greatest rainfall to occur sometime during the next several hours for Kauai. Radar has been showing mostly moderate rain so far with rates of 1 to 2 inches per hour. A band of heavier rain is currently moving through Kauai at the moment and due to the recent heavy rainfall and impacts, we are closely monitoring Kauai for additional flooding impacts and a Flash Flood Warning may be needed depending on how long this band holds over Kauai. Conditions should begin to gradually improve over Kauai later this afternoon as this frontal boundary shifts further east towards Oahu and Maui County. Over on Oahu and Maui County, we should see periods of moderate rain begin to increase with the heaviest rain expected this afternoon through the evening for Oahu and tonight into Monday morning for Maui County. A Flood Watch is in effect through Monday afternoon for Oahu and Maui County. With this event rainfall rates are not expected to be very high, so our main flooding concern will be over urban and poor drainage areas where steady moderate to locally heavy rain can cause issues. Currently on the Big Island, we do have a High Wind Warning starting at noon for the summits due to a strong subtropical jet nosing into our area. A Wind Advisory also goes into effect for Haleakala on Maui at noon today and goes through Monday afternoon. Over on the Big Island this afternoon, we should see scattered showers develop along the slopes with some snow showers at the summits. Overall the snow levels remain high and any snow that does fall will likely be wet heavy snow on the summits. A Winter Weather Advisory is in effect for the summits of the Big Island through tonight. As the frontal boundary approaches the Big Island on Monday, the main moisture and instability should pass north of the Island. So overall, we do expect showers to increase over the Big Island, but rainfall amounts should remain at light to moderate levels. By Tuesday, the frontal boundary should be northeast of the Big Island, with northwest to north winds expected behind the front. Shallow cumulus clouds behind the front could produce some light showers. By Wednesday afternoon, a ridge of high pressure will be building north of the state and our typical northeast trade winds should return. Some moisture is expected to ride in with the trade winds during the second half of the week and we should expected scattered showers across windward areas and isolated showers over leeward areas. && .AVIATION... A cold front will bring a band of heavy showers to Kauai during the next several hours. MVFR to IFR conditions are anticipated during this time, particularly over leeward slopes. The band of showers will then shift east bringing similar conditions to Oahu this afternoon and then Maui County this evening into tonight as the front stalls. Behind the front, winds veer to westerly and stable conditions prevail with nothing more than isolated to scattered light showers in the post frontal environment. AIRMET Sierra for mountain obscuration remains in effect for Kauai and will likely be issued for Oahu during midday followed by portions of Maui County tonight. AIRMET Tango for turbulence downstream of mountain ranges remains in effect for Kauai and Oahu. AIRMET Tango may also be needed for tempo moderate upper turb FL280-FL450 by midday. Light icing will be possible within the resident cloud layer between approximately 140-FL200. && .MARINE... South to southeast winds will strengthen ahead of an approaching front today. A Small Craft Advisory remains posted for coastal waters west of and including the Kaiwi Channel due to winds. The front will slowly push eastward today through Monday, before stalling out and slowly dissipating near the Big Island Tuesday and Wednesday. Light to moderate west to northwest winds will fill in behind the front. Winds will become rather light by Monday night and continue through Wednesday, with moderate trades potentially returning for the latter part of the week. North shore surf will remain small today. Surf will trend up tonight and Monday as a medium-period northwest swell arrives. Surf could reach low end advisory levels along north facing shores Monday night and Tuesday as a second, more north-northwest pulse arrives. This swell will then decline Wednesday through late in the week. Surf along east facing shores will continue to slowly decline today and Monday, with only small very small surf expected through the remainder of the upcoming work week. Small, medium to long period south swell will keep some small surf rolling into south facing shores through late in the week. && .HFO WATCHES/WARNINGS/ADVISORIES... Flood Watch through late tonight for Niihau-Kauai- Flood Watch through Monday afternoon for Waianae Coast-Oahu North Shore-Olomana-Central Oahu-Waianae Mountains-Lanai Mauka- Kahoolawe-Maui Windward West-Maui Leeward West-Haleakala Summit- East Honolulu-Honolulu Metro-Ewa Plain-Koolau Windward-Koolau Leeward-Molokai-Lanai Windward-Lanai Leeward-Lanai South-Maui Central Valley North-Maui Central Valley South-Windward Haleakala-Kipahulu-South Maui/Upcountry-South Haleakala. Wind Advisory from noon today to 6 PM HST Monday for Haleakala Summit. Winter Weather Advisory until 6 AM HST Monday for Big Island Summits. High Wind Warning from noon today to 6 PM HST Monday for Big Island Summits. Small Craft Advisory until 6 PM HST this evening for Kauai Northwest Waters-Kauai Windward Waters-Kauai Leeward Waters- Kauai Channel-Oahu Windward Waters-Oahu Leeward Waters-Kaiwi Channel. && $$ DISCUSSION...Kino AVIATION...JVC MARINE...Foster
