Area Forecast Discussion
Issued by NWS Honolulu, HI

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923
FXHW60 PHFO 180158
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
358 PM HST Fri Oct 17 2025

.SYNOPSIS...

An upper level low to our west has been aiding in thunderstorm
development west of Kauai/Niihau today. As this system weakens and
drifts west, a new upper level low will move toward the state from
the northeast. A trough will connect these features, helping to
maintain relatively unstable conditions, will be draped over the
area through the end of next week. Moderate to locally strong
trade winds will be unaffected by these upper level features, and
are forecast to continue. This combination will continue to bring
enhanced showers and a slight chance of thunderstorms to the
region this weekend.

&&

.DISCUSSION...
Radar and satellite show isolated showers across the state this
afternoon, with thunderstorms once again remaining well off the
coast. There is still a slight chance the western part of the
state could see a thunderstorm through tomorrow. Otherwise, expect
a continuation of moderate to locally strong trades, and showers
focused mainly windward and mauka. An upper level trough will
remain over the area for the coming week, keeping conditions
slightly more unstable than usual. Within that trough, two
separate closed circulations will impact the area`s weather. The
first is west of the area and moving away. The second will move in
from the northeast and should end up centered very close to us by
Wednesday. Importantly, the coldest air aloft is not forecast to
follow the closed circulation all the way down to a position
overhead, but should stay north. This will limit the thunderstorm
potential for the middle of next week. Models depict several
periods of slightly enhanced moisture moving through, with the
first one coming in tonight. We do expect to see a relatively wet
period with showers moving quickly within the trade winds from ENE
to WSW. This will carry them from windward areas into leeward
areas a little more than typically occurs. The next one should
arrive Monday night, with another potentially arriving Wednesday.
Confidence in the timing of this final one is not high. Finally,
trades are forecast to weaken slightly Sunday through Wednesday,
but not really enough to boost sea- and land-breeze effects.

&&

.AVIATION...
An upper level low pressure system west of the state continues to
create an unstable atmosphere allowing enhanced showers to be
embedded within easterly trade winds. These showers are mostly
focused over windward and mountain areas, but they can spread into
leeward areas as well. MVFR conditions are expected within
passing showers, otherwise VFR conditions prevail.

AIRMET SIERRA is not in effect, but could be issued tonight due
to potential low clouds and showers causing mountain obscurations.

AIRMET Tango is in effect across the island chain for tempo
moderate turbulence between FL300 and FL350. Conditions will
continue through the evening but will likely weaken later
tonight.

High clouds streaming over Maui and the Big Island are causing
light icing conditions in LYR 155-FL210. These conditions are
expected to continue through the evening, but chances of light
icing should decrease late tonight.

&&

.MARINE...
Moderate to locally strong trades will remain in place over the
Hawaiian coastal waters through Saturday. Trade winds will then
weaken into the moderate to locally fresh range through early next
week. A Small Craft Advisory (SCA) remains in effect over the
windier waters and channels surrounding Maui County and the Big
Island through Saturday afternoon. An upper low north of Kauai will
continue to drift over the northern waters through the weekend
keeping a slight chance of thunderstorms in the forecast.

Two moderate, long-period NW and NNW swells moving through the
waters will keep surf heights elevated along N and W facing
shores through Saturday. Surf along N and W facing shores will
slowly trend down on Sunday. A hurricane force low E of Japan will
bring another round of moderate, long-period NW (330 deg) swell
into the islands towards the middle of next week building surf
heights along N and W facing shores. This next long-period swell
may possibly reach low-end High Surf Advisory levels Wednesday
into Thursday.

A series of small, medium- to long-period S to SW swells will
continue to filter into the area through the weekend keeping surf
along S facing shores from going flat. Short-period surf along E
facing shores increases slightly on Saturday due to the stronger
trades, then trends down slightly Sunday through early next week.

&&

.FIRE WEATHER...
Wind speeds and humidity levels will remain below critical fire
weather thresholds through the forecast period. Brief heavy rain
and isolated thunderstorms are possible through Saturday.
Unstable conditions will continue to produce wet weather across
the state through next week. Temperature inversion heights near
Maui and the Big Island will range from 7,000 to 8,000 feet MSL
through Saturday.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
Small Craft Advisory until 6 PM HST Saturday for Maalaea Bay-
Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters-Big
Island Southeast Waters.

&&

$$


DISCUSSION...Parker
AVIATION...Wroe
MARINE...Ahue
FIRE WEATHER...Parker