168
FXHW60 PHFO 262000
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
1000 AM HST Sat Apr 26 2025

.SYNOPSIS...
Light winds will prevail through early next week, with land and
sea breezes common over most of the state. A rather dry pattern
will persist today, with a few showers affecting east and
southeast facing slopes this morning, and a few leeward showers
developing this afternoon. The airmass will moisten up tomorrow
through Tuesday, bringing an increasing shower activity across the
state. Some of the showers could be heavy and isolated
thunderstorms will be possible early next week as a disturbance
aloft dives southward over the state. A return to more typical
trade wind weather featuring mainly windward and mauka showers
appears take hold during the middle to latter part of next week.

&&

.DISCUSSION...
Current radar and satellite imagery show a cluster of showers
with a few embedded thunderstorms to the west of Kauai and a weak
convergent boundary to its east producing a few showers in the
Kauai Channel this morning. Otherwise, the rest of the state is
looking mostly dry with light to moderate southeast winds ushering
in clouds and a few light showers to windward areas, and sea
breezes just beginning to develop - building clouds over leeward
and interior areas, as well.

The surface trough to the west of Kauai producing that cluster of
showers with embedded isolated thunderstorms will remain somewhat
stationary today and then gradually drift eastward towards Kauai
tomorrow, increasing the chance for rain over and near Kauai.
However, rainfall amounts with this feature are not expected to
be a concern at this time. For the rest of the state, high
pressure to the distant northeast and the surface trough west of
Kauai will maintain light to moderate southeast winds that will
focus sporadic clouds and showers over east and southeast-facing
coasts and slopes. These lighter winds will be conducive for sea
breeze development each afternoon and land breeze development
overnight, which will in turn bring clouds and a few showers to
interior and leeward areas each day and clearing of these areas
overnight. Today will be relatively dry as drier air filters in,
keeping only isolated to scattered showers in the forecast.
Tomorrow, the trough/front with its moisture axis will move over
Kauai and a batch of moisture will ride in on the southeast flow
across the rest of the state, increasing rain chances.

On Monday, a shortwave trough will form a cutoff low that will
dive southwest towards and then across the state through midweek.
Lingering moisture combined with broad surface troughing and the
instability and dynamic forcing the upper level low is expected to
bring will enhance showers and bring the potential for heavy rain
and thunderstorms Monday through Tuesday or Wednesday. Model
guidance suggests that the most active weather day will be on
Tuesday, when the upper level low is almost centered over the
state and 500mb temperatures drop to near -13C.

Heading into the latter part of the week, moderate to breezy
trades are expected to return as high pressure to the northeast
begins to dominate, focusing periodic clouds and showers over
windward and mauka areas. In the wake of the upper level low that
will weaken and push east, ridging will build over the area,
increasing atmospheric stability.

Finally, volcanic gas emissions combined with the light southeast
flow will likely keep vog across the state through early next
week.

&&

.AVIATION...
Light southerly winds this weekend. Land/sea breezes will develop
over each island through Sunday. Fairly stable conditions aloft
will keep SHRA activity to a minimum through the rest of today,
with a slight increase in SHRA tomorrow.

&&

.MARINE...
A front and trough northwest of Kauai continues to bring some
heavier showers and thunderstorms to the nearby coastal and
offshore waters. This boundary is expected to slowly lift to the
northeast over the next couple of days, and then push south
towards the islands again Monday or Tuesday. As it does so, there
will be another chance for thunderstorms over the coastal and
offshore waters. Southeast winds are expected to give way to
light and variable winds Sunday as the boundary weakens. Trades
eventually return midweek as surface high pressure builds north of
the region.

A small long-period northwest swell is forecast to cross the local
waters today, peak tonight into Sunday, then fade through early
next week. This incoming swell has already reached Hanalei buoy
early this morning, with the latest observation indicating the
presence of long period energy. Surf along north and west facing
shores should remain near or below average, well shy of High Surf
Advisory (HSA) criteria. By Thursday, a medium long-period north
northwest swell is progged to enter the waters and produce surf
that may approach HSA.

Multiple small early season south swells will maintain small
background southerly energy through mid next week. A bump up in
south swell energy is expected to arrive late Thursday and last
through next weekend. Weak upstream trade wind flow will keep surf
along east facing shores near or below seasonal averages.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$


DISCUSSION...Farris
AVIATION...Walsh
MARINE...M Ballard