377
FXHW60 PHFO 081926
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
926 AM HST Wed Jan 8 2025

.SYNOPSIS...
A cold front and its associated showers, will impact Oahu today,
then stall before reaching Molokai later today through Thursday.
Lingering moisture combined with an upper disturbance moving into
the area will keep rainfall chances elevated through the second
half of the week. As trade winds gradually return, the focus of
rainfall will shift to windward and mauka areas later in the week
through early next week.

&&

.DISCUSSION...
A cold front is currently just west of Oahu, with an associated
diffuse band of showers beginning to move into western portions of
Oahu this morning. Ahead of the front, spotty and brief showers
will continue to develop and lift northward today. With southwest
flow prevailing ahead of the front, rainfall will primarily favor
west and south facing slopes, with brief heavier showers possible.
Rainfall associated with this main line of showers exceeded an inch
for parts of Kauai as it moved through, which will also be possible
over portions of Oahu during the next 24 hours. Short-term model
guidance remains in good agreement with the front continuing eastward
across Oahu through the rest of the morning before stalling between
Oahu and Molokai later today through Thursday. While most of the
dynamics and deeper moisture are expected to remain to the north,
enough low-level moisture is being pulled northward over the state
to keep the rainfall chances up. Moderate southwest winds will
gradually ease through the day as the front stalls.

Winds have shifted out of the west-northwest behind the front over
Kauai this morning, which supports the best chance for mainly light,
post-frontal rainfall continuing over west-through north-facing slopes
for Kauai (and Oahu once the front moves through) today. Northeast to
east trade winds will return statewide Thursday through the weekend
as high pressure builds to the north. Residual moisture near the stalled
front, combined with an upper trough moving through and eventually
closing off over the eastern half of the state, will sustain rainfall
chances into the second half of the week. With the trades in place,
rainfall will primarily focus over windward and mauka areas.

Additional instability from the cold pool aloft may also lead to a
few heavier showers or even isolated thunderstorms Thursday and Friday
as the upper trough moves into the area and begins to close off. Some
elevated stream response possible, along with the potential need for
a flood advisory or two. For the Big Island summits, this setup could
support periods of wintry precipitation from late Thursday through
Saturday.

&&

.AVIATION...
A cold front will gradually move across Oahu through the day today,
then stall between Oahu and Molokai later today and tonight. Moderate
to breezy northerly winds will trickle in behind the front by this
afternoon or evening. Showers along and behind the frontal boundary
will bring MVFR conditions to Oahu and parts of Kauai today and into
tonight. Otherwise, south to southwesterly winds will allow brief
periods of low clouds and showers to develop over south and west-
facing slopes of the rest of the island chain with VFR conditions
generally prevailing.

AIRMET Sierra for mountain obscuration remains in effect for Oahu
as the front moves through and is expected to bring MVFR conditions.

&&

.MARINE...
An extra-large WNW swell will bring dangerously high surf to
exposed N and W facing shores through Thursday. With peak surf
heights near 40 feet expected in exposed locations today, a High
Surf Warning remains posted for most N and W facing shores. Swells
of varying periods will arrive concurrently, with shorter-period
"fresh swell" arriving in conjunction with longer-period swells,
leading to somewhat jumbled surf conditions, and more consistent
sets.

Overnight observations from NDBC buoys 51001/51101 NW of Kauai
have been fairly consistent, with significant wave heights
consistently above 18 feet. As these swells propagate through
island waters, resultant surf will peak this afternoon, then
gradually diminish into Saturday. Surf heights will likely fall
below High Surf Warning levels Thursday night, and below High Surf
Advisory heights by Saturday. A new, moderate northwest swell is
possible Sunday. With the swell so large, combined seas 10 feet or
greater have warranted a Small Craft Advisory for all Hawaiian
coastal waters (except Maalaea Bay) through Thursday.

A cold front is currently just west of Oahu, moving E at 10 to 15
kt. The front is expected to stall between Oahu and Molokai this
evening then gradually dissipate. Light south to southwest winds
immediately ahead of the front will become light to moderate west
to northwest winds with frontal passage. Winds over Big Island and
Maui waters will remain light and variable through tonight. Associated
precipitation should be light today and limited to Kauai and
Oahu.

The dissipating low-level boundary associated with the stalled
front will then diminish through Thursday night as high pressure
builds N of the islands, leading to moderate to fresh trade winds
statewide that will persist through the weekend.

Although the frontal boundary will dissipate, lingering moisture
will become enhanced by a developing low aloft that will begin to
destabilize the island atmosphere tonight. The low will persist
for several days, bringing the potential for isolated thunderstorms
and locally heavy downpours from late tonight into the weekend.

&&

.FIRE WEATHER...
No critical fire weather conditions are expected through the week
due to increasing moisture and rain chances associated with a
front forecast to move across the western islands today and stall
across the central part of the state tonight into Thursday.
Enhanced tradewind showers with the potential for isolated
thunderstorms are forecast through the rest of the week into the
weekend.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
High Surf Warning until 6 PM HST Thursday for Niihau-Kauai
Leeward-Waianae Coast-Oahu North Shore-Maui Windward West-Kona-
Kohala-Kauai North-Molokai Windward-Molokai North-Molokai West-
Maui Central Valley North-Windward Haleakala-Big Island South.

Small Craft Advisory until 6 PM HST Thursday for all Hawaiian
waters except Maalaea Bay-

&&

$$

DISCUSSION/FIRE WEATHER...TS
AVIATION...Farris
MARINE...Bedal