160
FXHW60 PHFO 200155
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
355 PM HST Sat Apr 19 2025

.SYNOPSIS...
Trade winds have returned to the islands, but will remain light
enough for seas breezes through this evening. Moderate trades
then continue through Monday, with clouds and showers favoring
windward and mauka areas. Another storm system will approach the
state from the northwest towards the middle of next week bringing
a chance of heavy rain and thunderstorm Tuesday through Thursday.

&&

.DISCUSSION...
Radar and satellite imagery continue to show scattered showers
across the state this afternoon under light to moderate trade
winds as surface high pressure far north of the state builds.
However, trades across the region are currently light enough to
allow for the development of sea breeze clouds and showers over
island interiors. Meanwhile, 00Z upper air obs from Lihue continue
to show a relatively unstable (1400 J/kg MUCAPE) and moist (1.36
in PW) air mass across the region as a diffuse upper level trough
weakens northeast of the state. This lingering instability and
moisture will help to enhance some showers today, with some areas
in upcountry Maui getting close to 0.5 in over the last several
hours. Expect the threat for localized flooding to continue
through this evening.

Otherwise, expect the upper level trough to continue to weaken
overnight as upper level ridging expands towards the west. At the
surface we will see moderate easterly trade winds expand by Sunday
and continue into Monday as clouds and showers favor windward and
mauka areas.

The next weather maker will come in the form of a closed-off upper
level low that will sink down along and near 170W longitude and
come within 600 miles northwest of Kauai. The west-northwest
positioning of this low will pull up more moisture-rich air over
the state from the southwest. As heights begin to lower and mid to
upper layers cool from the west, enhanced instability within a
moistened air mass will likely induce another round of widespread
heavy showers and thunderstorms. Guidance continues to show the
highest rain probabilities across the western half of the state.
Expect another round of flood concerns next Tuesday through
Thursday as locally heavy rain falls upon saturated soils. If
guidance holds would not be surprised if a Flood Watch is issued
for portions of the state in the coming days.

&&

.AVIATION...
Moderate trades have returned and will persist through tomorrow,
ushering clouds and showers into windward and mauka areas.
However, winds will be light enough to support isolated sea/land
breeze development that will bring additional clouds and showers
to some leeward and interior areas during the afternoon hours and
clearing of these areas overnight. MVFR conditions will be
possible in any showers, otherwise VFR conditions should prevail.

No AIRMETs are currently in effect.

&&

.MARINE...
Gentle to moderate trades continue through Monday, then veer to
southeasterly in advance of a deep low that will develop NW of the
islands. Winds further veer through midweek and then hold steady
out of the southerly quadrant where they will remain for the
balance of the week. There will be a chance of thunderstorms
during this time, particularly over the western waters.

A moderate, medium period NNW swell has shifted more N and will
gradually trend down through Sunday producing below average surf
along N and W facing shores. A tiny, long period NW swell will
fill in Monday into Tuesday before subsiding Wednesday which will
prevent surf from going flat. In the long range, guidance depicts
a gale forming Monday near the Kurils then tracking northeast to
the western Aleutians by Wednesday. In this scenario, Hawaii
would experience an uptick in the NW swell next weekend.

Surf along E facing shores will remain below the April average
through the weekend. E shore surf could becomes tiny by mid week
as southerly winds emerge.

A tiny, long period S swell will move through this weekend
providing a small boost in surf along S facing shores. A larger,
long- period SSW swell will fill in Monday into Tuesday and
produce near to above average surf along S facing shores.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
None.

&&

$$

DISCUSSION...Ahue
AVIATION...Farris
MARINE...JVC