Area Forecast Discussion   Issued: 03/10/2026 05:08:00 PM UTC

                        
468
FXHW60 PHFO 100708
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
908 PM HST Mon Mar 9 2026

.SYNOPSIS...
A powerful kona storm is expected to affect the state this week
and into the weekend, bringing several potential hazards to the
islands. The combination of deep tropical moisture, strong winds,
and increasing instability could produce periods of heavy rainfall
with significant flash flooding, damaging winds, and strong to
severe thunderstorms from Tuesday through at least Saturday.
Flooding concerns may begin as early as Tuesday and Tuesday night
over Kauai and Oahu as deep moisture spreads into the western end
of the state, then expands eastward across the island chain later
in the week. The potential for strong to severe thunderstorms is
expected to increase late in the week and into the weekend.

&&

.SHORT TERM UPDATE...
Issued at 903 PM HST Mon Mar 9 2026

Current observations show winds have veered to a southeast
direction and radar shows some showers with embedded thunderstorms
approaching the coastal waters west of Niihau. These thunderstorms
are expected to continue their eastward track through the night.
We are also watching some light to moderate showers develop over
the Koolau mountains. The forecast so far remains on track.

&&

.PREV DISCUSSION...
The weather regime heading into the evening is expected to be
rather typical of a veered east-southeast flow for the eastern
half of the state with showers generally favoring the southeast
and east facing slopes of the Big Island and Maui. For the western
end of the state, showers with embedded thunderstorms will begin
to move in from the west.

Forecast confidence continues to increase regarding the wet and
unsettled pattern that is expected to develop tomorrow through the
rest of the week and weekend. Impacts, including the potential
for significant flash flooding, damaging winds, and strong to
severe thunderstorms, will initially be felt across the western
end of the state and will gradually expand eastward over the next
several days. While this is a long duration event, it looks like
the overall evolution can be broken into two primary stages.

The initial stage is expected to start tomorrow or tomorrow night
and potentially last through Thursday. As a broad low deepens to
the northwest of the state, winds will veer southerly for the
western half of the state and southeasterly for the eastern half
heading into Tuesday. A broad swath of deep atmospheric moisture
with precipitable water values (PWats) ranging from 1.5 to 2
inches, which can be seen as an area of showers and thunderstorms
roughly 200 miles west-northwest of Kauai this afternoon, will be
drawn up in this southerly flow and move over the western end of
the state Tuesday into Wednesday. At the same time, a shortwave
will round the base of a potent upper level trough to the
northwest, providing instability, and upper level jet dynamics
will support large scale ascent across the area. Together, these
ingredients will support periods of heavy rainfall with embedded
thunderstorms and gusty winds. Impacts during this stage are
expected to be focused primarily across the western half of the
state.

The second stage looks to start on Friday and persist into the
weekend. The upper level trough to the northwest will continue to
sharpen and take on a negative tilt as a jet streak on its western
flank strengthens and another shortwave trough will round the
base of this trough. The axis of deep atmospheric moisture will
shift eastward and spread out across the island chain, with model
guidance showing PWats exceeding 2 inches. By late week and into
the weekend, soils may already be saturated, increasing the
likelihood that additional rainfall will produce rapid runoff and
dangerous flooding conditions, increasing flooding concerns
statewide, particularly where heavier rainfall persists over the
same areas for multiple days. While thunderstorms embedded within
showers are possible midweek as mentioned above, the potential for
strong to severe thunderstorms will increase Friday into the
weekend as the environment becomes increasingly unstable, moisture
increases and the upper level jet dynamics become even more
favorable for large scale ascent.

In addition to the rainfall threat, south to southwest winds may
strengthen later in the week and into the weekend as the pressure
gradient tightens between the developing low to the northwest and
high pressure to the east. If this materializes, strong kona winds
and localized downslope winds on north through east facing sides
of the islands may be capable of downing trees and power lines.

For the Big Island summits, increasing moisture and colder air
associated with the upper trough may support periods of heavy
snowfall with significant accumulations later in the week and into
the weekend, potentially requiring the issuance of a winter storm
watch/warning.

While some uncertainty remains regarding the exact timing and
placement of the heaviest rainfall and strongest storms,
confidence continues to increase that the islands will experience
a prolonged period of unsettled and potentially impactful weather
this week. Residents and interests across the state should
continue monitoring forecasts as details regarding the timing and
location of impacts become clearer.

&&

.AVIATION...
Issued at 903 PM HST Mon Mar 9 2026
Rainfall and thunderstorm chances will quickly ramp up overnight
through Tuesday across the western end of the state, particularly
over Kauai tonight, as a powerful kona low evolves and draws
closer. This activity will lead to MVFR conditions, with LIFR
conditions expected in the heavier showers and storms that move
through.

Light to moderate southeast winds will gradually veer southerly
and increase over the western end of the state through the day
Tuesday. Any storms that develop and move through will be capable
of producing damaging winds. These impacts will gradually advance
eastward down the island chain by midweek.

AIRMET ZULU is in effect for light icing for Kauai and Oahu.
AIRMET SIERRA for mountain obscuration will likely be needed
overnight through Tuesday, especially for Kauai and Oahu.
Additionally, AIRMET TANGO for turbulence may also become
necessary.


&&

.MARINE...
Issued at 903 PM HST Mon Mar 9 2026

A powerful kona storm is expected to bring heavy rain,
thunderstorms, and rough seas to the islands and adjacent waters
Tuesday into the weekend. Winds will veer southerly and increase
to fresh to locally strong speeds Tuesday through late this week
as the kona storm approaches. A Small Craft Advisory (SCA) will
go into effect for waters north and west of Kauai beginning early
Tuesday morning, when winds will begin to increase. Later this
week, possibly as early as Thursday night, winds will approach,
or possibly reach, gale force for portions of the area. These
strong winds will slowly creep eastward with the front heading
into the weekend.

A series of small, medium- to long-period west-northwest swells
returning tonight will bring small surf to north and west facing
shores through the rest of the week. The first of these will peak
on Tuesday, resulting in a slight bump in surf along north and
west- facing shores. Another small, medium-period north swell is
also possible late this week.

Choppy surf along east-facing shores will gradually trend
downward, falling below seasonal levels by mid-week as winds veer
southerly. Surf along south-facing shores will remain small,
though will become rough and choppy as southerly winds increase.
A series of small, long-period south swells will also impact
south-facing shores through late this week.


&&

.HFO WATCHES/WARNINGS/ADVISORIES...
Flood Watch from 6 AM HST Tuesday through Saturday afternoon for
Kauai East-Kauai Mountains-Kauai North-Kauai South-Kauai
Southwest-Niihau.

Flood Watch from Tuesday evening through Saturday afternoon for
Central Oahu-East Honolulu-Ewa Plain-Honolulu Metro-Koolau
Leeward-Koolau Windward-Oahu North Shore-Olomana-Waianae Coast-
Waianae Mountains.

Flood Watch from Wednesday morning through Saturday afternoon
for Haleakala Summit-Kahoolawe-Kipahulu-Lanai Leeward-Lanai
Mauka-Lanai South-Lanai Windward-Maui Central Valley North-Maui
Central Valley South-Maui Leeward West-Maui Windward West-
Molokai Leeward South-Molokai North-Molokai Southeast-Molokai
West-Molokai Windward-South Haleakala-South Maui/Upcountry-
Windward Haleakala.

Small Craft Advisory from 6 AM Tuesday to 6 AM HST Wednesday for
Kauai Leeward Waters-Kauai Northwest Waters-Kauai Windward
Waters.


&&

$$

SHORT TERM UPDATE...Tsamous
DISCUSSION...Farris
AVIATION...Gibbs
MARINE...Vaughan