Area Forecast Discussion
Issued by NWS Honolulu, HI
Issued by NWS Honolulu, HI
669 FXHW60 PHFO 280640 AFDHFO Area Forecast Discussion National Weather Service Honolulu HI 840 PM HST Thu Jun 27 2024 .SYNOPSIS... A high pressure ridge will remain in place north of Hawaii into next week, producing moderate trade winds through the weekend, and then strengthening into the moderate to breezy range from Monday onward. Passing showers are expected to mainly affect windward and mountain areas, favoring the overnight to early morning hours. An upper level low will drift from east to west over the islands this weekend, likely increasing shower activity as it passes through the state. Isolated thunderstorms are possible over the interior Big Island and near Kauai this weekend. && .DISCUSSION... Water vapor channel satellite imagery this evening shows an upper level low roughly 600 miles northeast of Hilo, Hawaii. This low will slowly drift westward across the island chain this weekend, enhancing trade wind showers as it passes through the state. Infrared and visible satellite imagery shows a band of unstable low clouds riding into the islands on the trade winds tonight, likely increasing shower activity into the early morning hours. Global weather models continue to show a slight weakening of the ridge induced trade winds through the weekend, as the upper low passes over the region. Isolated thunderstorms are possible over the Big Island interior on Saturday afternoon and then near Kauai from Saturday night to Sunday. The ridge north of the island chain will then strengthen after the upper low passes to the west, increasing trade winds into the moderate to breezy range from Monday onward. The strengthening ridge will also keep the trade wind thermal inversion at more stable and lower heights next week with limited shower activity forecast for most of the days. && .AVIATION... Moderate trades are expected to continue through tomorrow across the island chain. Showers and low clouds embedded in the trades could bring brief periods of MVFR conditions over windward and mauka locations. Otherwise, VFR conditions should prevail. No AIRMETs are in effect at this time. However, a band of clouds and showers approaching the island chain from the east this evening, may bring more persistent MVFR conditions to some windward areas overnight and AIRMET Sierra for tempo mountain obscuration may be needed. In addition, an upper-level low is forecasted to approach the islands this weekend. This could increase shower coverage. As such AIRMET Sierra may be needed periodically throughout the weekend. && .MARINE... High pressure north of the state will maintain moderate to fresh trade winds through the weekend. The trades are expected to strengthen back to fresh and strong levels early next week, and a Small Craft Advisory will likely be required for the typically windy waters around Maui and the Big Island. A series of south swells will keep south shore surf near the summertime average through the weekend. Surf will lower below normal levels much of next week. A small northwest swell will give a small boost to north shore surf on Friday, 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 up and closer to seasonal levels next week as the trades strengthen over and upstream of the islands. && .HFO WATCHES/WARNINGS/ADVISORIES... None. && $$ DISCUSSION...Bohlin AVIATION...Farris MARINE...Jelsema