Area Forecast Discussion   Issued: 03/22/2026 11:36:00 AM UTC

                        
597
FXHW60 PHFO 220136
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
336 PM HST Sat Mar 21 2026

.SYNOPSIS...
Our kona storm will remain with us through Sunday for most
islands, but the threat of flooding has become low enough for
Kauai and Niihau that the flood watch has been cancelled there.
For the remainder of the state, expect periods of showers, some
heavy, to continue tonight and Sunday. As the system moves off to
the east Sunday night and Monday, trades will return from west to
east Monday into Monday night and then continue through the end of
the week. Windward showers will be scattered to numerous Monday
into Monday night, then decrease for the remainder of the week.


&&

.DISCUSSION...
Issued at 335 PM HST Sat Mar 21 2026

Radar shows showers and isolated thunderstorms moving northeast
over parts of the state. The largest area of showers as of 3 PM
HST was over Maui County, with showers also over parts of the Big
Island (mainly N and S Hilo).

The upper level trough that has brought us this kona storm
continues to drift slowly east as it evolves, with shortwaves
moving through the trough. Today, the associated surface low has
started to move northeast away from the state. This is the
beginning of the end of this system. However, it will remain close
enough for a continued threat of flash flooding from Oahu east
through the Big Island through Sunday afternoon. Flood warnings
remain in effect this afternoon for much of Maui County. Periods
of showers and isolated thunderstorms are still expected tonight
and Sunday. Moisture levels remain high and cold temperatures
aloft will bring continued instability. Therefore, rainfall rates
have the potential to be high.

Sunday night and Monday, the upper trough will weaken and slowly
slide across and east of the state. At the same time, the surface
low will move significantly farther away. This will allow a high
pressure center to build in to the north of the state, and trade
winds will return Monday to the western islands, and Monday night
to the eastern islands. Low level moisture left over from the kona
storm will result in scattered windward showers on western and
central islands Monday, with numerous showers on windward Big
Island into Monday night. From Tuesday through the end of the
week, expect typical trade wind weather, with isolated to
scattered showers windward and very few if any showers on the
leeward side.


&&

.AVIATION...
Issued at 335 PM HST Sat Mar 21 2026

Bands of showers and embedded thunderstorms continue to move over
Maui County, with Oahu starting to see some showers redevelop as
well. The ongoing kona low will support further rain bands, mainly
across Oahu and Maui County, through the forecast period. Rainfall
may spread to Kauai and the Big Island at times, though confidence
is lower for those areas. Winds will remain primarily out of the
south to southwest. Expect widespread MVFR conditions over Maui
County and Oahu at times through the forecast period, with locally
LIFR conditions under showers.

AIRMET Sierra is in effect for Molokai, Maui, and Lanai due to
widespread low ceilings and showers and is expected to continue
for at least the next few hours. Oahu may need to be put back
under a mountain obscuration AIRMET as showers increase again this
evening.

AIRMET Tango remains in effect for moderate turbulence downwind
of terrain for Oahu and Maui County below 070 from gusty south to
southwest winds associated with the kona low. However, winds are
showing some signs of weakening, so we may be able to cancel this
AIRMET later tonight or Sunday.

Light icing in layer 140-FL260 will also persist, mainly over the
central portion of the state where the thick high clouds continue
to stream over from the southwest.

&&

.MARINE...
Issued at 335 PM HST Sat Mar 21 2026
Bands of heavy showers and a few thunderstorms will continue to move
over portions of the coastal waters, especially the central and
eastern waters, as a kona low continues to impact the state.
Prevailing southerly moderate to locally breezy winds continue
across portions of the area as well. The low will lift farther
north on Sunday, allowing light to moderate northerly winds to
develop around Kauai, which will then veer to northeast and spread
southward. Additionally, due to wave heights around Niihau, Kauai,
and Oahu near 10 feet, a Small Craft Advisory remains in effect
for those waters until 6AM Sunday.

A northerly swell is peaking today, and is producing borderline
advisory-level surf for north facing shores of Niihau, Kauai, and
Oahu as of this afternoon. This will continue into the evening
hours before slowly declining overnight. As such, a High Surf
Advisory (HSA) remains in effect for north facing shores for
Niihau, Kauai, and Oahu until 6AM Sunday. Additionally, a slight
bump is expected from a small, building west-northwest swell that
will peak Sunday.

A small south swell is slowly declining and will continue to
trend down through the rest of the weekend into early next week.
Smaller surf is expected along south facing shores through the
remainder of the week. Surf along east-facing shores remains
elevated due to wrap from the north swell, and will be near HSA
thresholds. This swell will slowly diminish through the rest of
the weekend as well.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
Flood Watch through Sunday afternoon for Big Island East-Big
Island Interior-Big Island North-Big Island South-Big Island
Southeast-Central Oahu-East Honolulu-Ewa Plain-Haleakala Summit-
Honolulu Metro-Kahoolawe-Kauai Mountains-Kauai North-Kipahulu-
Kohala-Kona-Koolau Leeward-Koolau Windward-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-Niihau-Oahu North Shore-Olomana-South
Haleakala-South Maui/Upcountry-Waianae Coast-Waianae Mountains-
Windward Haleakala.

High Surf Advisory until 6 AM HST Sunday for Kauai East-Kauai
North-Koolau Windward-Niihau-Oahu North Shore-Olomana.

Winter Storm Warning until 6 PM HST Sunday for Big Island
Summits.

Small Craft Advisory until 6 AM HST Sunday for Kaiwi Channel-
Kauai Channel-Kauai Leeward Waters-Kauai Northwest Waters-Kauai
Windward Waters-Oahu Windward Waters.


&&

$$

DISCUSSION...Parker
AVIATION...TS
MARINE...Vaughan