Area Forecast Discussion for Hawaii

Area Forecast Discussion   Issued: 04/13/2026 04:06:00 PM UTC

                        
916
FXHW60 PHFO 130606
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
806 PM HST Sun Apr 12 2026

.SYNOPSIS...
Light to moderate rain will continue through tonight over the
western portion of the state. A few showers may be locally heavy.
Quieter weather then settles in for the remainder of the week and
light trades return by week`s end.

&&

.SHORT TERM UPDATE...
Issued at 802 PM HST Sun Apr 12 2026

Latest radar imagery depicts light rainfall continuing over the
western portion of the state. The most recent One-Hour Rainfall
Summary (730 PM HST) shows most locations that are experiencing
rain are receiving under a tenth of an inch in the last hour, with
some areas a bit higher. The Flood Watch remains in effect
through 6 AM HST Monday and will be reevaluated with the morning
forecast package. Otherwise, the current forecast remains on track
and no major amendments have been required this evening.

&&

.PREV DISCUSSION...

Nil instability, weak forcing, and rather high mid-level static
stability have allowed Oahu to dodge a potentially impactful
flooding event. Little change is expected during the next several
hours, so rain rates are expected to remain in check. Cancelling
the Flood Watch for Big Island. Will draw back the ending time
for Kauai through Maui to 6am tomorrow morning. Elected to retain
portions of the Flood Watch to account for the onset of the
favorable diurnal cooling period and ongoing convection in Maui
County within the surface trough axis. As forcing weakens, so too
will rain rates. Light showers and mid-level clouds are likely to
linger over the western end of the state for the balance of the
week before another shortwave pivots through and brings a slight
uptick in rainfall on Friday or Friday night. This wave is modeled
to be progressive and and likely not impactful.

Despite the grungy pattern that may hang over Kauai and Oahu through
the week, for the first time in awhile, there is no potential event
on the horizon. The large scale pattern is gradually migrating away
from aggregate low pressure anchoring north of the islands, though
high pressure struggles to build as the mid-latitudes transition
toward a more progressive pattern. Light winds favoring onshore
sea breezes each afternoon may trigger rather productive
convection in terms of showers as the moisture-rich airmass
lingers. Likewise, dewpoints will hover around 70 degrees until
the dregs of this airmass are ushered westward by returning
trades. Trades do return by late this week, but remain quite
light and may not make much of a dent in local humidity.

&&

.AVIATION...
Issued at 802 PM HST Sun Apr 12 2026

Low cigs and SHRA will continue over the islands through the
overnight into tomorrow. MVFR and some isol IFR conds possible
especially across the western side of the state. Winds should
remain light.

AIRMET Sierra is in effect for mtn obsc for Kauai to Maui. This
may be expanded to include the Big Island.

AIRMET Tango is in effect for mod turb btn 120-FL280. Conds should
slowly improve into tomorrow.


&&

.MARINE...

A weak surface trough will linger in the vicinity of the central
and northwestern islands into early next week, keeping moderate
to fresh southeasterly winds to its east, and light to moderate
southerly winds to its west. This weak surface boundary along
with an upper level disturbance moving over the region is
currently bringing another round of showers and the potential for
isolated thunderstorms this afternoon into Monday. As the surface
trough lifts northwest and high pressure to the northeast begins
to take over at the surface, gentle to moderate easterly trades
will gradually develop across the Hawaiian coastal waters by the
end of the week.

A moderate, medium-period north-northwest swell (340 degrees)
generated by the formerly-gale force low north-northwest of the
main Hawaiian islands is filling in along north and west facing
shores this afternoon. This swell will maintain small to moderate
surf through Monday, followed by a decline in northwest swell
energy for the rest of the week.

A medium-period south swell will continue to decline through Monday.
By Tuesday, however, a new south swell will arrive, once again
providing a boost to surf along south facing shores through mid week
before gradually subsiding into the weekend.

Surf along east facing shores will remain 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 until 6 AM HST Monday for Niihau, Kauai, Oahu,
Molokai, Lanai, Maui, and Kahoolawe.


&&

$$

SHORT TERM UPDATE...Pierce
DISCUSSION...JVC
AVIATION...Walsh
MARINE...Farris