Wailuku, Hawaii 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

074
FXHW60 PHFO 111911
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
911 AM HST Sat Apr 11 2026

.SYNOPSIS...

A band of showers, some heavy, will develop over the western half
of the state tonight and bring rainfall early next week. Winds
remain light through much of the forecast period with moderate
trades building in by the end of the week.


&&

.SHORT TERM UPDATE...
Issued at 902 AM HST Sat Apr 11 2026

Dry air filling in behind the departing low brings high stability
to the Lihue sounding this morning while Hilo remains saturated to
the tropopause. However, developing subsidence and weak dry
advection will scour this moisture out today. Radar returns have
rapidly dimished over the Big Island and the forecast has been
updated accordingly.

Scattered light showers continue lifting SW-NE in the Kaiwi
Channel and western Maui County. These showers are developing
along a weakly convergent remnant surface boundary where SW mid-
level winds have already begun advecting deeper moisture back into
the central portion of the state. These showers will remain light
in the very near term, but the boundary could serve as a focus
for afternoon convection as it wavers between Oahu and Molokai.
However, ample high clouds limit confidence for heavy afternoon
showers as depicted in the latest hi-res.

Although radar presentation this morning remains modest, model
cross-sections are actually impressive with how quickly a deep,
convergent frontal structure redevelops over central Hawaii. As
right entrance jet forcing increases tonight, the front rapidly
builds to jet level and is modeled to have an appreciable frontal
circulation in the presence of otherwise very weak forcing. This
sets the stage for a rather narrow band of fairly stationary
shower activity to develop over or in the vicinity of Oahu
tonight. The hi-res guidance is very aggressive in depicting heavy
rainfall potential, though these models tend to run hot in
moisture-rich environments. Even so, the global models also key in
on a narrow band of moderate to heavy rain that may not move much
for 24 hours or so. Several inches of rain will be possible
beneath this band, which is most likely to set up somewhere
between the Kauai Channel and Molokai, though Kauai and western
Maui are not out of the game. At this time, Oahu appears to be
the highest probability landing spot, but details governing the
ultimate position of the frontal band are likely to be lost in the
noise and uncertainty probably remains high until it becomes
evident on radar. Uncertainty is high enough to warrant keeping
Big Island in the statewide Flood Watch, but the probability of
meaningful rainfall is lowest there.


&&

.PREV DISCUSSION...
A residual axis of deep tropical moisture with bands of moderate
to heavy showers remains focused over the eastern end of the state
this morning, with Maui and the Big Island continuing to face the
potential for heavy rain. The shortwave responsible for the most
organized large-scale lift over the past couple of days continues
to pull north and away from the state. As a result, rainfall
intensity should steadily diminish somewhat through the day.

Elsewhere across the state, conditions are expected to remain
somewhat quieter through the day, with only a few passing showers
and overall lower rainfall chances, especially across Kauai and
Oahu where drier air has already begun to fill in. This
improvement, however, is expected to be temporary.

Guidance remains in good agreement showing another shortwave
rotating through the broad upper trough northwest of the state
later tonight into Sunday and then lingering into early next week.
This feature is expected to once again strengthen large-scale
ascent across the region while renewing the deep tropical moisture
plume across the islands.

As a result, another round of widespread showers with periods of
moderate to heavy rainfall appears increasingly likely beginning
later tonight, first across the western end of the state, then
expanding eastward through Sunday and potentially lingering into
early next week.

Antecedent conditions are now the primary concern statewide. With
soils remaining saturated, streams elevated, and some areas
having already received substantial rainfall totals over the past
48 hours, flooding impacts will be much easier to realize with
this next round of heavy rain. While some guidance continues to
suggest an additional several inches may be possible over the
duration of the next event, exact storm totals are less important
than rainfall intensity and duration. Any period of intense
rainfall rates could quickly lead to renewed flash flooding and
rapid rises in streams. As a result, the Flood Watch is now in
effect for all Hawaiian Islands through Monday afternoon.

One notable change heading into the extended period is the wind
pattern. The strong southerly winds associated with the initial
system over the past couple of days have weakened considerably,
with mainly light and variable winds expected from today through
much of next week. This lighter flow regime may allow heavier
showers to linger over localized areas for longer durations,
further increasing the flooding threat.

&&

.AVIATION...
Issued at 902 AM HST Sat Apr 11 2026

A band of layered clouds, along with lingering showers, will
reside over Molokai and eastward today. Less activity is expected
over the western islands, other than diurnally driven afternoon
interior showers over Oahu and Kauai. Windward Big Island could
also see some afternoon shower activity. MVFR ceilings and
visibility with isolated IFR conditions will be possible with any
of the heavier shower activity. Expect sea and land breezes today
for the western half of the state, while light to moderate S - SE
winds remain for the eastern half.

A narrow band of moisture is expected to develop over the central
portions of the island chain as early as tonight. This band of
moisture will likely bring another round of heavier showers with
isolated thunderstorms through Monday morning.

AIRMET Sierra is in effect for mountain obscuration above 1500 ft
for Molokai, and for IFR conditions over Oahu and Lanai. IFR
conditions will likely diminish with diurnal heating later this
morning, but mountain obscurations may still remain throughout
the day.

AIRMET Zulu remains in effect for moderate icing between
140-FL200 from Maui eastward to Big Island, but conditions will
likely diminish later today.


&&

.MARINE...
A low pressure system that is currently north-northwest of the
main Hawaiian Islands continues to draw moisture across the area
this morning. Showers are continuing across the central and
eastern coastal waters, though upper-level support is expected to
diminish today. A trough will linger in the vicinity of the
islands into early next week, however, keeping winds lighter than
seasonal average. Additional support for showers and isolated
thunderstorms will return to the region by tonight into Sunday.
East of the trough, moderate to fresh southeasterly winds will
prevail, while winds west of trough will be light and variable,
which may become southerly next week but remain generally light.

As southerly winds continue to decline today, surf along south-
facing shores will return smoother, less choppy conditions.
Additionally, the medium-period south swell will gradually decline
through the weekend. By Tuesday, however, a new south swell will
arrive, once again providing a boost to surf along south facing
shores.

A moderate, short to medium-period northwest swell generated by
the gale force low to the northwest will bring a boost to surf
along north and west facing shores today. Another northwest
reinforcement on Sunday will maintain this small to moderate surf
through the weekend, followed by a decline in northwest swell
energy next week.

Surf along east facing shores remains below seasonal average with
lighter than average trade winds near and upstream of the islands
forecast through next week.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
Flood Watch through Monday afternoon for Hawaii.


&&

$$

SHORT TERM UPDATE...JVC
DISCUSSION...Gibbs
AVIATION...DT
MARINE...Vaughan