Hawaii National Park, Hawaii Weather Forecast Discussion

176
FXHW60 PHFO 181352
AFDHFO
Area Forecast Discussion
National Weather Service Honolulu HI
352 AM HST Thu Sep 18 2025
.SYNOPSIS...
Moderate to breezy trade winds remains in the forecast for the
foreseeable future. Brief passing showers are expected through
Friday, mainly over windward and mountain areas in the overnight
to early morning hours. The unstable cloud remnants of an old
frontal band will drift through the islands from Friday night into
Saturday, boosting cloud and rain shower coverage for all islands.
These enhanced clouds and showers will linger over the windward
slopes of the Big Island through Sunday, while other islands will
return to a more typical brief passing shower pattern. By next
week Tuesday, a weak upper level low drifts over the Hawaii
Region, enhancing clouds and showers once again with the potential
for wet weather trends.
&&
.DISCUSSION...
The satellite imagery this morning shows a subtropical jet stream
over the Big Island with high clouds over the eastern edge of the
state. Brief showers continue to drift over windward and mountain
areas on local radar.
Weather conditions trend towards the wet side from Friday night
into Saturday as an unstable cloud band, associated with the
remnants of an old East Pacific cold front, will drift through the
islands on the trade winds. Low level forcing and instability
along this cloud band will boost trade wind showers statewide,
favoring windward and mountain areas. The strongest shower bands
will likely bring some much needed rainfall to favored leeward
areas. A portion of this unstable cloud band will linger through
Sunday along the windward slopes of the Big Island. As more
stable conditions will return to the rest of the state.
Back to more typical brief passing showers in a moderate to breezy
trade wind pattern through Monday. A weak upper level low drifts
over the Hawaii Region by next week Tuesday, briefly boosting
shower activity across the state through early Wednesday morning.
We increased precipitation chances to account for this cold core
unstable upper low over the islands during this time period.
&&
.AVIATION...
Moderate to breezy trade winds will continue for the next several
days. Although some clouds and showers embedded within the trades
will be possible for windward and mountain areas, VFR flight
conditions are expected to prevail for most locations.
AIRMET Tango remains in effect for moderate low level turbulence
over and downwind of island terrain. This AIRMET will likely be
needed for the next several days as breezy trades persist.
&&
.MARINE...
High pressure to the north-northeast of the area will remain in
place for the next several days, keeping moderate to locally
strong trade winds across the islands. The current Small Craft
Advisory (SCA) is in effect for the typical windy areas as well as
the Oahu Kauai channel. A week trough northeast of the islands is
expected to marginally weaken trade winds today. This will bring
the locally strong winds back to the typical windy waters around
the Big Island and Maui, as well as windward Maui. SCA winds for
typical windy areas are then possible through the weekend.
Surf along south facing shores will be small today and tonight
with mainly background south and southeast energy. A small to
moderate, long- period, south southwest swell will build Friday
evening into Sunday and help boost south shore surf heights back
up to near or above the September average. This swell will then
gradually decrease next week.
Surf along north facing shores should see a small increase today
as a short period northerly swell fills in. This small bump is
expected to peak on Friday out of the north to north- northeast
direction, followed by a short period north northwest swell this
weekend. Moderate to locally strong trades near and upstream of
the area will lead to choppy conditions along east facing shores
over the next several days. A slight increase of windswell is
expected over the weekend due to a fetch of strong winds northeast
of the state.
&&
.FIRE WEATHER...
Humidity levels and wind speeds will remain just below critical
fire weather thresholds this week. A few periods of unsettled
weather conditions will increase humidity levels, clouds and
shower chances from Friday night through Saturday, and from
Tuesday morning into Wednesday. Temperature inversion heights near
the Big Island and Maui today will range from 6,000 to 7,000 feet
elevation.
&&
.HFO WATCHES/WARNINGS/ADVISORIES...
Small Craft Advisory until 6 AM HST early this morning for Kauai
Leeward Waters-Kauai Channel.
Small Craft Advisory until 6 PM HST this evening for Maui County
Windward Waters.
Small Craft Advisory until 6 PM HST Friday for Maalaea Bay-
Pailolo Channel-Alenuihaha Channel-Big Island Leeward Waters-Big
Island Southeast Waters.
&&
$$
DISCUSSION...Bohlin
AVIATION...Bohlin
MARINE...Tsamous
FIRE WEATHER...Bohlin

NWS HFO Office Area Forecast Discussion