672
FXHW60 PHFO 151511 CCA
AFDHFO

Area Forecast Discussion...CORRECTED
National Weather Service Honolulu HI
511 AM HST Sat Nov 15 2025


.SYNOPSIS...
Light to locally breezy trades with generally drier weekend
weather. There are increasing chances for more inclement, active
weather next week.

&&

.DISCUSSION...
Broad upper ridging west of the region, centered along 20N, will
expand eastward and envelope the Hawaiian Islands and its
surrounding waters. A 1029 mb surface high pressure located
approximately 1,200 miles from Oahu is weakening and settling
southeastward. 12Z soundings are depicting very dry mid level air
advecting in from the east. All of these factors equate to an
evolving stable weather pattern and will result in drier weather
under lighter winds. This drier air mass will move across the area
early today and assist in ending the overnight persistent
windward Big Island precipitation. Many rain gauges in the Hilo
and Puna Districts have picked up 2 to 5 inches of rain since
early Friday morning. A nice trade wind pattern weekend under
partially sunny skies and light trades, locally breezy within
higher terrain. Light precipitation will focus along windward
upslope mauka with higher nocturnal rain accumulations within an
overnight relatively deeper moistened boundary layer squeezed
underneath a thick layer of dry air aloft. The next couple of days
will be the best weather days of the upcoming week.

A weakness will develop within the upper ridge over the islands on
Monday. An upper trough and associated cold front will approach
the island chain from the northwest and merge with the weakness
channel over the state going ito Tuesday. It is a bit early to
determine the evolution of this trough but it will more than
likely pull up moist equatorial air while destabilizing the
regional atmosphere. The trough or upper low will cool 500 mb
temperatures to around -10 C and this instability will increase
the probabilities of isolated thunderstorms across the central
islands of Oahu and Maui County from late Monday through Tuesday
afternoon. Numerous showers that may produce locally heavy rain
will be the main theme Monday through Wednesday. Freezing levels
falling to around 12k feet, along with the potential of a
saturated column between -10 and -20 C Tuesday, implies a frozen
mix or brief snow showers atop Big Island`s summits. Mid level
winds will strengthen east of the upper trough axis going into mid
week and this may increase Haleakala and Big Island summit winds
to near Wind Advisory levels (in gust) Monday night and Tuesday.
The cold front will slow as it approaches the western half of the
state Wednesday. This feature, along with a mid level trough
moving across from the east within a highly moistened regional air
mass, should provide the necessary ingredients of lift and
instability to possibly prolong this wet pattern into next
weekend.

&&

.AVIATION...
Trade winds are decreasing in magnitude with a diminished threat
for regional turbulence over and in the vicinity of the islands.
Occasional showers will occur across windward areas and higher
terrain. The greatest threat for continued precipitation and
mountain obscuration (occasional MVFR) this morning remains over
windward exposures, especially Big Island.

AIRMET Sierra remains in effect for windward Big Island. This
will continue through mid morning to account for the upstream
moist air mass being lifted along windward Mauna Kea and Mauna
Loa`s slopes.


&&

.MARINE...
Moderate to locally strong easterly trade winds will persist
today and gradually weaken as high pressure to the northeast
slowly drifts southeast and weakens. A Small Craft Advisory (SCA)
has been trimmed back this morning to the typical windy waters and
channels around Maui County and the Big Island through this
afternoon. Guidance for early next week remains uncertain with the
potential for an upper level trough forming southeast of the
coastal waters Monday and moving northwest over the islands. The
moderate trade winds may veer to the east-southeast and slowly
weaken through Tuesday. Additionally, a front looks to move into
the offshore waters by Tuesday afternoon, bringing locally strong
east-northeast winds behind the front, before weakening over the
coastal waters midweek. There is a potential for isolated to
scattered thunderstorms over the marine waters Monday through
Wednesday.

Surf along north facing shores will remain small through midday
before a small to moderate, medium to long period northwest swell
looks to fill in this afternoon that will keep surf elevated
through the weekend. Tiny long period forerunners have started to
show up on the NDBC offshore buoy 51101 early this morning. A
moderate long period northwest swell is expected to arrive late
Tuesday, and peak Wednesday near High Surf Advisory (HSA) levels
before declining by the end of next week.

Surf along east facing shores will continue to decline through
the weekend due to the weakening of the local and upstream trade
winds. Large choppy short period surf for north and exposed east
shores is possible by the middle of next week depending on the
evolution of the potential trough and approaching cold front
mentioned above. For south shores, tiny background southerly
swell will remain through the forecast period.


&&

.FIRE WEATHER...
Recent island wide rain and more overcast skies, along with relatively
higher minimum afternoon humidities under light winds, will all help
maintain a lower fire weather threat. The potential exists for a
wet weather pattern through most of next week. This morning`s
lower inversion height slopes from near 4k ft the western islands
to around 9k ft on Big Island.


&&

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


&&

$$


DISCUSSION...Blood
AVIATION...Blood
MARINE...Shigesato
FIRE WEATHER...Blood