968
FXHW60 PHFO 271948
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
948 AM HST Mon May 27 2024

.SYNOPSIS...
High pressure northeast of the state will maintain moderate to
locally breezy easterly trade winds through the week. Showers will
mainly favor windward and mauka areas, especially during the
overnight through early morning hours each day. A drier trade wind
pattern is expected during the second half of the week.

&&

.DISCUSSION...
Moderate to locally breezy trade winds continue across the
islands today with broad high pressure north of the state. Latest
regional satellite imagery shows an area of showers and
thunderstorms associated with a nearly stationary surface trough
and its attendant low aloft. These thunderstorms are now located
about 250 nm west of Kauai, just outside of the offshore waters.
Early morning soundings from Lihue and Hilo showed mostly stable
conditions with temperature inversions between 6000 and 7000 ft.
Showers that were more common earlier this morning across windward
Oahu have noticeably decreased since about 7am HST, though a
narrow band of low-level moisture embedded within the trades
continues to produce scattered light showers and clouds across
eastern sections of Maui and Molokai. In the near term, shower
chances and coverage have been lowered through the rest of the
morning for much of the Big Island, which is located south of the
primary band of low-level moisture affecting Maui County.
However, the overall forecast philosophy remains in tact.

Little change is expected in the overall pattern for the rest of
Memorial Day, as high pressure gradually strengthens to the
north/northeast and the surface trough and upper low west of the
state remain nearly stationary. Shallow moisture embedded within
the trades will produce some windward and mauka showers at times,
particularly tonight through early Tuesday. Additionally, expect
spotty afternoon and evening showers across leeward portions of
the Big Island.

The low aloft west of the islands will swing around to the
northeast tonight through Wednesday. This will bring the area of
enhanced showers/thunderstorms closest to the main Hawaiian
Islands- within in the offshore waters, and possibly grazing the
far NW coastal waters, during this time. However, guidance
remains in agreement that the trough will remain far enough west
of the state to have little impact on island weather as ridging
aloft builds from the south and the surface high to the far
northeast strengthens.

For the rest of the week, the surface high far northeast of the
state will gradually strengthen and hold into the weekend. Expect
increasing stability and a drier trade wind pattern during the
second half of the week.

&&

.AVIATION...
Moisture riding in on the moderate to breezy trade winds will
bring clouds and showers to windward and mauka areas, with better
coverage expected during the overnight to early morning hours.
MVFR conditions will be possible with this activity. Otherwise and
elsewhere, VFR conditions will prevail. This pattern will hold
over the next couple of days.

AIRMET Sierra is in effect for mountain obscuration for windward
Big Island and N through SE sections of the smaller islands. This
AIRMET may be cancelled later this morning or afternoon as
conditions improve.

AIRMET Tango remains in effect for moderate low-level turbulence
downwind of island terrain.

With a weak shortwave trough passing just west of the state today
and increased mid level clouds around Kauai, the potential exists
for light icing between 160 and FL250 for this afternoon through
tonight.

&&

.MARINE...
Moderate to strong easterly trades will continue through the week
as the surface ridge remains positioned north of the state. The
strongest winds are expected over the windier waters around Maui
County and the Big Island, supporting the Small Craft Advisory.
The lightest winds are anticipated over the Kauai waters,
fluctuating between east and east-southeast over the next few days
due to a persistent surface trough to the west. A shift out of
the east-northeast is likely later in the week as the trough
weakens and drifts away from the region.

Surf along exposed south-facing shores will remain small
throughout much of the week, due to a combination of background
south-southwest and southeast swell energy. An upward trend is
expected from Friday through the first week of June due to an
active pattern setting up within our swell window near New
Zealand.

Altimeter and ASCAT passes over the past couple of days reflected
the potential for next weekend, showing a broad swath of gale-to
storm-force winds with seas up to 30 feet focused at the state
within the 190-200 degree directional bands. This will mark the
beginning of a long-lived event with additional reinforcements
expected within the same area over the next several days.

Surf along exposed east-facing shores will remain small and
choppy throughout the week as the trades persist.

Surf along north-facing shores will remain near the summertime
average each day, with only small background northwest pulses
expected today and potentially next weekend.

&&

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

&&

$$

DISCUSSION...Vaughan
AVIATION...Farris
MARINE...JVC