Royal Kunia, Hawaii 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

374
FXHW60 PHFO 070101
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
301 PM HST Fri Mar 6 2026

.SYNOPSIS...

Trade wind weather will continue through the weekend with brief
passing showers favoring windward and mountain areas of all
islands. Winds begin to shift out of the south from Sunday night
into Monday as a strong cutoff low pressure system approaches from
the northwest. Strong southerly winds will draw deep tropical
moisture northward increasing the threat for widespread heavy
rainfall and severe weather through much of next week.


&&

.DISCUSSION...
Issued at 300 PM HST Fri Mar 6 2026

Satellite shows increasing high clouds moving in from the west,
along with the typical trade-wind cumulus at lower levels moving
from ESE to WNW. Radar shows scattered to numerous light showers,
mainly in windward and mountain areas. General low level wind flow
was from the ESE, with terrain altering that flow in most leeward
areas. Showers are expected to continue, and even become slightly
more numerous, tonight.

We still see a significant weather system reaching the western end
of the main islands Monday into Monday night, then extending
eastward to all islands by Wednesday or Thursday. The potential
for heavy rain, flooding, thunderstorms, and strong winds will
last into next weekend for at least part of the state.

Models (deterministic and ensemble) are in fairly good agreement,
especially considering the time frame involved, on the overall
evolution of this event. High-over-low blocking patterns will
become established both to our east and northwest this weekend.
The closed upper level low to our northwest will strengthen and
then remain in roughly the same area all next week. Even though
this feature is over 1000 miles away, it will be the dominant
factor in our weather next week. The low level circulation that
forms beneath this upper feature will switch our winds to
southerly. This will draw moisture northward, increasing our PW
values from current levels of just over one inch to just over 2
inches.

Cold air aloft will help destabilize the atmosphere, and we will
likely see thunderstorms over parts of the area from Tuesday into
next weekend. Several shortwave troughs are likely to rotate
around the closed upper low and then move toward/over the state
next week. As they do, winds will increase at all levels,
increasing advection of moisture and providing shear that aids the
formation of strong showers and thunderstorms. At this time, the
most significant of these shortwaves is forecast to move through
the state Wednesday or Thursday. However, "lesser" shortwaves,
impossible to exactly time, will still have the potential to
bring heavy rain and gusty winds along with the accompanying
showers and thunderstorms.

Timing: the western end of the state may be impacted as early as
late Monday into Monday night, with the threat spreading east over
the entire state Tuesday into Wednesday. The threat will then
linger into next weekend due to the blocking pattern referenced
above. The pattern just isn`t expected to change much. Models show
a significant flow of moisture over the state the entire time, and
it may even extend beyond next weekend.

There are many details that will only become discernible when we
get closer in time (exact timing of shortwave troughs, for
example), so please stay up to date as this event approaches. When
the stronger parts of the system move through, the potential for
flash flooding is appearing more likely with each new model run.
This is an unusually long-lasting system, and impacts are likely
to stack up over time as the ground becomes saturated by repeated
rains.

&&

.AVIATION...
Issued at 300 PM HST Fri Mar 6 2026

East-southeast are beginning to pick up this afternoon and will
continue to do so for the next 24 to 48 hours. VFR will prevail
today, with brief periods of MVFR possible along east and southeast
facing slopes due to low clouds and intermittent light showers
moving in on the winds. No AIRMETs are currently in effect nor
expected through the period.

&&

.MARINE...
Issued at 300 PM HST Fri Mar 6 2026

Fresh to strong east to southeast winds associated with a surface
ridge extending southwest into the region will remain in place
through the weekend. Expect the strongest winds and roughest
conditions within the channels, along the Hamakua Coast of the Big
Island, windward waters, and south of the Big Island. A Small
Craft Advisory has been expanded and extended to add the Kaiwi
channel and Oahu windward waters through Saturday night. As the
surface ridge begins to weaken early next week, a broad low
pressure is expected to develop nearby to the west. This pattern
will cause winds to veer out of the south to south- southeast,
potentially remaining in the fresh to strong range next week.

Surf along east facing shores will elevated and choppy into early
next week due to a large upstream fetch of fresh to strong
breezes extending across the northeast Pacific. A downward trend
is expected next week as this pattern weakens and local winds veer
southerly.

Surf along north- and west-facing shores will remain relatively
small through the period, with only a few west-northwest pulses
expected over the weekend. A small medium period west-northwest
(300 deg) swell is expected to slowly fill in Saturday and peak
Sunday near head-high levels. A small long-period westerly (290
deg) swell associated with a slow- moving storm- force low
tracking eastward toward the Date Line from the far northwest
Pacific is expected early next week. However, the westerly winds
associated with this system near the islands are forecast to
weaken by the weekend, which will limit the amount of swell
generated toward the state. Additionally, Kauai will block some of
this energy from reaching other coasts across the island chain.

Surf along south-facing shores exposed to southeast trade-wind
seas will gradually increase through the weekend. Conditions could
become rough early next week as winds veer southerly and
strengthen. A long-period south-southwest swell associated with a
recent system passing through our swell window near New Zealand
is expected to arrive Tuesday and persist through midweek.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
Small Craft Advisory until 6 AM HST Sunday for Alenuihaha
Channel-Big Island Leeward Waters-Big Island Southeast Waters-
Big Island Windward Waters-Kaiwi Channel-Maui County Leeward
Waters-Maui County Windward Waters-Oahu Windward Waters-Pailolo
Channel.


&&

$$

DISCUSSION...Parker
AVIATION...TS
MARINE...Shigesato