National Weather Service Weather Forecast Office

• Home
• Site Map
• News
• Organization
• Search for: NWS All NOAA 

000
FXHW60 PHFO 140155
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
355 PM HST Sat Apr 13 2024

.SYNOPSIS...
A frontal boundary currently located within the vicinity of Kauai
will produce breezy southerly winds and periods of heavy rain and
thunderstorms across the western half of the state. The initial
threat for flash flooding with this system is highest for the
islands of Kauai and Niihau from later tonight through Sunday
night. These showers will then decrease in intensity as the front
weakens and moves across the eastern half of the state from Monday
through Tuesday. As the frontal boundary moves through each
island, west winds will follow with improving weather conditions.
Light to moderate trade wind weather will return during the
second half of the week.

&&

.DISCUSSION...
A low pressure system currently centered around 775 miles
northwest of Kauai and its associated front clearly seen on
satellite located roughly 100 miles west and northwest of Kauai
will begin to approach the state and will bring the threat of
heavy rain over Kauai as early as tonight, but more likely early
Sunday into Sunday afternoon. The Flood Watch goes into effect at
midnight tonight.

Thunderstorms have been developing along the frontal boundary just
west and north of Kauai during the day today with showers clipping
Kauai throughout the afternoon. Starting tonight as the frontal
boundary slowly creeps towards Kauai, breezy southerly winds will
be on the increase and will bring an increase of moisture. Latest
sounding from Lihue already shows abundant moisture with
precipitable water values over 1.8 inches. In the upper levels of
the atmosphere, we do have a shortwave trough digging towards the
state, which should help ramp up the heavy showers and isolated
thunderstorms late tonight. At this time, the main instability
seems to be north of the state, so the threat for severe
thunderstorms will remain low. Overall, this event looks to be a
heavy rain event with gusty winds at times with any thunderstorms.
Latest forecast has 3 to 6 inches of rain with isolated pockets
of up to 10 inches for Kauai early Sunday morning through Sunday
night. Due to the recent heavy rainfall, it will likely not take
much to cause flooding issues on Kauai.

As the frontal boundary gradually progresses eastward on Sunday,
showers will be on the increase for Oahu and parts of Maui County.
The frontal boundary should be weakening as it moves eastward,
thus rainfall amounts should be less than on Kauai. The main
moisture band is expected to reach Oahu Sunday afternoon into the
evening and over Maui County Sunday night into Monday. We are
currently monitoring the threat for flash flooding over on Oahu
and Maui County and a Flood Watch will be possible for these
islands late Sunday into Monday. By the time the frontal boundary
reaches the Big Island late Monday into Tuesday, rainfall amounts
should be much less and is not expected to cause a flood threat
on the Big Island at this time. Our typical trade wind weather
should return during the second half of next week.


&&

.AVIATION...
Within prevailing southerly flow, clouds and showers will favor
south and southeast facing slopes and coasts. Additional showers
may develop over interior and windward areas tomorrow afternoon.
Showers and thunderstorms will increase over the western islands
tonight as a front approaches from the west.

AIRMET Tango remains in effect for moderate upper level
turbulence between FL180 and FL380. These conditions will likely
hold through tonight.

AIRMET Zulu remains in effect for moderate rime icing in cloud, in
precipitation, between FL230 and FL280 due to layered clouds over
and around the Big Island. This AIRMET will likely be needed
through tonight.

&&

.MARINE...
South to southeast winds will strengthen tonight ahead of an
approaching front to the west. A Small Craft Advisory has been
posted for coastal waters west of an including the Kaiwi Channel
due to winds. The front will slowly push southeast through
Monday, before stalling out and slowly dissipating near the Big
Island Tuesday and Wednesday. Light to moderate west to northwest
winds will fill in behind the front. Winds will become rather
light by Monday night and continue through next Wednesday, with
moderate trades potentially returning for the latter part of next
week.

North shore surf will remain small through the rest of the weekend.
Surf will trend up Sunday night and Monday as a medium-period
northwest swell arrives. Surf could reach low end advisory levels
along north facing shores Monday night and Tuesday as a second,
more north-northwest pulse arrives. This swell then on the
decline Wednesday through late next week. Surf along east facing
shores will decline over the weekend, with only small very small
surf expected through the upcoming week. Small, medium to long
period south swell will continue into next week.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
Flood Watch from midnight HST tonight through late Sunday night
for Niihau-Kauai-

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


&&

$$


DISCUSSION...Kino
AVIATION...Powell
MARINE...Foster