670
FXHW60 PHFO 270635
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
835 PM HST Fri Apr 26 2024

.SYNOPSIS...

Strong trade winds will gradually ease and veer toward the east-
southeast through early next week. Plumes of moisture will produce
passing showers across windward and mountain areas through
Saturday. A drier weather pattern is expected Sunday into early
next week with light to moderate east to east-southeast winds.
Winds should be light enough for sea breezes to develop during the
day and land breezes at night, especially early next week.


&&

.DISCUSSION...

Latest satellite and radar imagery shows shower coverage
increasing mainly across windward and mountain areas this evening
with more bands of showers developing south of Kauai. Shower
activity is expected to continue and become more moderate rest of
tonight into early morning Saturday, with showers focused over
windward and mountain areas and scattered showers over leeward
areas. Breezy winds will hold through tonight as a 1032 mb high
pressure system sits 1200 miles northeast of the state and a 1016
mb surface low pressure develops 900 miles northwest of the state.

As the day goes on Saturday the low will shift northeast as the
high weakens slightly. A ridge of high pressure will develop
north of the state weakening and veering winds out of the east-
southeast, especially over the western half of the state. Showers
will generally decrease through the day with the exception of
leeward areas. With winds becoming more east- southeast and
weakening, this should allow sea breezes to develop over leeward
areas, leading to afternoon clouds and showers. A drier air mass
is expected to move in by Sunday, so overall we should less
showers on Sunday as well as lighter winds with sea breezes
developing over many leeward areas Sunday afternoon.

For early next week, high pressure will be centered far northeast
of the state, while a low pressure system shifts north of the
state. We will be in a hybrid wind pattern early next week with
light to moderate east-southeast winds over windward areas and
generally light winds over leeward areas. Due to limited moisture,
we are not expecting much rainfall early next week, but some
light passing showers should be expected over windward areas, as
well as some light showers over leeward areas during the afternoon
with the sea breezes developing.

For the second half of next week, latest guidance is showing
quite a bit of uncertainty with an upper level trough moving over
the area. The ECMWF shows a much deeper upper level trough with a
surface trough developing near the state. Meanwhile, the GFS is
shows a much weaker upper level trough, with the surface high
north of the state maintaining trade winds during the second half
of the week. Stay tuned to the extended forecast, as the forecast
will change over the next several days. The current forecast
aligns more with the GFS due to it being closer to climatology for
this time of year.


&&

.AVIATION...
Moderate to locally strong E trade winds will ease and veer to the
ESE over the weekend, especially over the smaller islands. AIRMET
Tango for low-level turbulence will likely be pared back, removing
at least Kauai and Oahu on Saturday. An increased amount of showery
low clouds moving in on the trade wind flow has led to the issuance
of AIRMET Sierra for most windward areas, where periods of MVFR
VIS/CIG in SHRA may be briefly punctuated by short-lived IFR VIS
in +SHRA. Guidance indicates the overnight development of a low-
level trough over the islands, with the trough potentially
lingering through Saturday, thus supporting continued periods of
MVFR conditions over windward areas.


&&

.MARINE...

A 1032 mb surface high, centered around 1000 nm northeast of the
state, will remain nearly stationary through tonight and allow
moderate to locally breezy easterly trade winds to persist. From
this weekend through early next week, this feature is expected to
drift slowly eastward. Low pressure deepening well northwest of
Hawaii will help to gradually veer these winds east southeasterly
and weaken them.

A Small Craft Advisory (SCA) remains in effect for most waters
and channels surrounding Big Island, Maui, and Molokai. As winds
further weaken overnight, more zones will be dropped from the
advisory. By 6 am HST, only the Alenuihaha Channel is expected to
remain at or above SCA criteria.

Surf heights will remain below advisory thresholds for all shores
through the forecast period. A small northwest, medium period
swell will peak tonight, then slowly subside through the weekend.
Thus, expect small surf to continue along north and northwest
facing shores. Breezy trade winds will produce choppy, rough surf
along east facing shores through Saturday. Conditions are expected
to improve on Sunday as the easterly flow weakens slightly and
veers southeast. Meanwhile, expect small surf along south facing
shores through the forecast period with occasional pulses of 1 to
2 foot medium to long period swell.


&&

.HFO WATCHES/WARNINGS/ADVISORIES...
Small Craft Advisory until 6 AM HST Saturday for Maui County
Windward Waters-Maui County Leeward Waters-Pailolo Channel-Big
Island Windward Waters-Big Island Leeward Waters.

Small Craft Advisory until 6 PM HST Saturday for Alenuihaha
Channel.


&&

$$


DISCUSSION...Almanza
AVIATION...Birchard
MARINE...Bedal