National Weather Service Weather Forecast Office

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

000
FXHW60 PHFO 130330
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
530 PM HST Fri Apr 12 2024

.UPDATE...Due to the lingering light snow showers over the summits
of the Big Island, the Winter Weather Advisory has been extended
through the morning. The snow showers should taper off over the
next several hours, but slick road conditions will likely continue
through the early morning hours. Winds have dropped below the
advisory thresholds for the summits of the Big Island, thus the
Wind Advisory has been cancelled. Strong winds are expected once
again over the summits Sunday night and could reach warning
levels.

&&

.SYNOPSIS...
A trough of low pressure will approach the state and will bring
another round of heavy rain starting over Kauai Saturday night
into Sunday, Oahu and Maui County Sunday night into Monday. As
this trough moves through the state from west to east, it should
weaken with mainly left over moisture expected over the Big
Island Monday night into Tuesday. Flooding will be the main
concern especially over Kauai due to the recent rainfall. Conditions
should improve later in the week with trades returning during the
second half of next week.

&&

.PREV DISCUSSION...
The strong low pressure system northwest of the state that
brought heavy rain and numerous thunderstorms over Kauai has
briefly lifted further north and weather conditions have somewhat
stabilized, thus the Flood Watch has been cancelled. For tonight,
showers will likely increase over Kauai, but the rainfall
intensities should remain at moderate levels. Some localized heavy
rain is still possible, but it is not expected to be prolonged.
Elsewhere, scattered showers will remain possible but should
generally be on the decrease.

Over on the summits of the Big Island, scattered snow showers
continue to persist this afternoon with strong winds. The snow
showers and the wind is expected to decrease this evening and will
likely drop below advisory levels sometime this evening. A Winter
Weather Advisory and a Wind Advisory remains in place through 6PM
this evening.

For Saturday, scattered showers and muggy conditions will
continue to linger over the western half of the state. Sea breezes
developing during the day should lead to increasing clouds during
the afternoon with scattered showers. Over the eastern half of the
state, mid to upper level clouds will continue to linger
especially over the Big Island. Scattered showers will continue
to ride in with the breezy east to southeast winds with afternoon
showers across the leeward slopes.

Starting Saturday night, a shortwave trough will dig towards the
state and will bring periods of widespread heavy rain across the
smaller islands. Flash flooding will once again be a concern over
Kauai and with the abundant rain that they received last night,
it will not take much to create more flooding concerns. So for
Kauai, the threat of heavy rain will begin to increase Saturday
night with the heaviest rain likely during the day Sunday. At this
time, the instability looks to be less than what we saw last
night, so the threat for severe thunderstorms will remain very
low. But with precipitable water values increasing to around 2
inches, flash flooding will be the main concern. A Flood Watch
should be reissued by Saturday morning over Kauai. As the upper
level trough continues to dig towards the state, the threat for
heavy rain will expand towards Oahu and Maui County Sunday night
into Monday and should weaken as it approaches the Big Island
Monday night into Tuesday. Our typical trade wind weather should
return during the second half of next week as a ridge of high
pressure builds north of the state.

&&

.AVIATION...
S to SE winds will gradually trend down over the next couple of
days. Clouds and showers have decreased over Kauai and Oahu today,
and will continue to do so through the night. Low clouds and
scattered showers will continue to be carried into E through SE
facing areas of the islands through Saturday, with brief periods
of MVFR conditions amid prevailing VFR. A slight chance of
thunderstorms remains through Saturday for the far western edge of
the Kauai coastal waters.

AIRMET Sierra remains in effect for mountain obscuration over E
through SE facing areas of the Big Island, as clouds and showers
continue.

AIRMET Tango remains in effect for tempo moderate turbulence
between 080 and FL180.

AIRMET Zulu remains in effect for light icing from Oahu through
Big Island, as layered mid- and upper-level clouds continue to
stream up from the southwest.

&&

.MARINE...
A deep surface low centered about 725 nm northwest of Kauai will
drift slowly northeast through tonight, then move slowly toward
the southeast and weaken Saturday and Sunday. The low and broad
high pressure to the east are producing mainly moderate to fresh
southeast winds across local waters, though winds are more
easterly around the Big Island and slightly weaker and southerly
around Kauai. As the low drifts northeastward tonight, expect
local winds to ease slightly and veer out of the southeast to
south, and the Small Craft Advisory (SCA) that had been in place
for most waters today has been cancelled. Isolated thunderstorms
will be possible around Kauai tonight. For Saturday and Sunday,
moderate to fresh southeast to south winds will prevail, and
another round of heavy showers and thunderstorms will develop
around Kauai late Saturday and push east to Oahu late Sunday.

The low will weaken considerably as it passes north then northeast
of the state Monday and Tuesday. A weak trough will move down the
island chain, bringing moderate west to northwest winds and
pushing a band of rainfall over the eastern half of the state. By
Wednesday, the trough will move to the east of the state, and
building high pressure to the northwest will drive moderate
northeasterly trades.

Small surf will persist across north facing shores through
tomorrow, with background energy from the northwest and north
expected. An upward trend is expected late Saturday and Sunday as
the arrival of a small long-period north-northwest swell
coincides with a more significant pulse of medium-period northwest
swell from the nearby surface low. Surf could reach low end High
Surf advisory levels Monday night through Tuesday. The swell will
decline Wednesday and Thursday as it shifts out of the north-
northwest.

Surf along east facing shores will decline over the weekend as
locally strong winds trend down and veer out of the south. Small
surf will persist next week.

A small, long-period south-southwest swell should arrive tonight
and hold through the weekend, but southerly winds will lead to
choppy conditions along southerly exposures. Another small pulse
of south swell will be possible Tuesday and Wednesday.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
Winter Weather Advisory until 6 AM HST Saturday for Big Island
Summits.


&&

$$


UPDATE...Kino
DISCUSSION...Kino
AVIATION...TS
MARINE...Wroe