Area Forecast Discussion for Hawaii

Area Forecast Discussion   Issued: 05/10/2026 05:28:00 AM UTC

                        
406
FXHW60 PHFO 091928
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
928 AM HST Sat May 9 2026

.SYNOPSIS...

A weak surface trough will gradually move east to west across the
islands through tonight, resulting in light winds and land/sea
breeze showers. As this trough dissipates, trades will build in
stronger through Monday. Trades will be on the increase Tuesday
onward.

&&

.SHORT TERM UPDATE...
Showers were moving across most of Kauai and Niihau this morning,
with mainly windward and mauka showers over Oahu and the islands of
Maui County. Winds were mostly northeast at 5 to 15 mph, with
occasional gusts of 20 to 25 mph in the typical windier locations.
We have done a small update this morning to increase the chance of
showers for the remainder of today in most areas, especially on
Big Island. The inversion height at Hilo this morning was around
11,000 feet, and we expect showers well up the mountains this
afternoon. Trade winds are still expected to continue building in
today, and increase in strength tonight and tomorrow.

&&

.PREV DISCUSSION...
Issued at 313 AM HST Sat May 9 2026

Windward and mauka showers with some limited spillover to leeward
areas are ongoing across the island chain. Satellite indicates
low clouds over or near the higher terrain on each island, along
with high clouds streaming in from the southwest.

A weak surface trough near Maui will slowly drift westward,
reaching Kauai on Sunday. Trade winds will build in behind this
trough from east to west through the weekend. Wind speeds will
initially be light to moderate, but will become moderate to
locally breezy into early next week. This trough will keep winds
weak enough to allow for land/sea-breeze showers to occasionally
develop over leeward areas, even as trade winds build in and bring
their typical windward and mauka focused showers.

While that is occurring at the surface, the flow aloft will change
significantly. We will transition from weak troughing to our
north this weekend to the rapid development of a closed ridge to
our northwest by Monday. This ridge will become elongated along an
east-west axis and remain with us all next week. Its presence
will keep a surface ridge in place, allowing the trades to blow at
least through the end of next week, and likely longer. This means
mainly windward and mauka showers will hang around. There will be
occasional fluctuations in available moisture throughout this
period, and these will result in periods of enhanced shower
activity from time to time.

&&

.AVIATION...
Moderate trades will steadily increase during the day today and
become locally breezy in select areas. A weak trough passing
through the state will increase showers, especially over windward
and mountain areas with periods of MVFR conditions expected
throughout the day today. A drier airmass will move in from the
east this evening, which should bring a decrease of showers
tonight. One exception is over Kauai, where showery conditions are
expected to persist through tonight.

AIRMET Sierra remains in effect for mountain obscuration over
Kauai, Oahu, Molokai and Maui due to the passing showers.

There may be the need for AIRMET Tango for low-level turbulence
as trades gradually strengthen.

&&

.MARINE...
A ridge will remain in place north of the islands with fresh
trade winds today, strengthening Sunday and maintaining next
week. A Small Craft Advisory (SCA) is posted for waters around
Kauai and windward Oahu today through tonight. The typical windy
waters around Maui County and Big Island will go into the SCA
tonight. The SCA will likely be expanded to more areas by Sunday
as winds strengthen.

A small northwest swell will maintain through the rest of the
weekend, shifting out of the north to north northwest next week.
Small south swell will fade this weekend with a small, long period
reinforcement Monday through Thursday. Surf along east facing
shores will remain below normal this weekend, but will gradually
increase next week as trade winds strengthen.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
Small Craft Advisory until 6 AM HST Sunday for Kauai Channel-
Kauai Leeward Waters-Kauai Northwest Waters-Kauai Windward
Waters-Oahu Windward Waters.

Small Craft Advisory from 6 PM this evening to 6 AM HST Sunday
for Alenuihaha Channel-Big Island Leeward Waters-Big Island
Southeast Waters-Maalaea Bay-Pailolo Channel.


&&

$$

SHORT TERM UPDATE...Parker
DISCUSSION...Walsh
AVIATION...Kino
MARINE...Foster