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Temp5.0 C
RH19 %
WindN 10 mph
RoadOpen (4x4)
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Hawaiian Islands Synoptic Discussion and Guidance

072
FXHW60 PHFO 250626
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
826 PM HST FRI JUN 24 2016

.SYNOPSIS...
Strong high pressure far north of Kauai will continue to generate
moderate to breezy trade winds into next week. An increase in
showers is expected for the smaller islands overnight as an area
of enhanced moisture embedded in the trades moves through the
state. Drier conditions are expected from midday Saturday through
the rest of the weekend, with passing showers favoring windward
and mountain areas, and just a few light showers leeward. The
Kona slopes of the Big Island will continue to see clouds and
widely scattered showers each afternoon and evening.

&&

.DISCUSSION...
Showers are quite active across the smaller islands from Maui
through Kauai this evening, as an area of enhanced moisture
embedded in the trade winds moves into the state from the east-
northeast. This so-called screaming eagle cloud formation is
associated with a weak low level trough. Mimic-TPW satellite
imagery also clearly shows this feature, with estimated PW values
up to 1.7 inches. A considerably drier airmass lies to the
northeast of the screaming eagle feature, with estimated PW values
dropping off to around 1 inch north of 24N and east of 155W.
Surface analysis depicts strong high pressure far north of the
state, driving fresh trades over the islands. The 00Z soundings
reflected a drier airmass ahead of the advancing area of moisture,
with PW values of 1.1 to 1.2 inches and typical inversion heights
between 6500 and 8000 feet.

Rather wet conditions will prevail overnight across windward
areas, especially over the smaller islands. Most of the showers
will be light to moderate, but rainfall totals could add up to 1
to 2 inches in the wettest spots due to the frequency of the
showers. Scattered showers will spill over into many leeward
areas of the smaller islands as well. Showers will likely increase
overnight across the windward Big Island, but it appears that the
bulk of the enhanced moisture will pass north of that island. The
existing forecast appears to be on track, and no updates are
planned for this evening.

The screaming eagle will move west of the state on Saturday
morning, with the drier airmass spreading in from the northeast.
This will result in a considerable decrease in shower activity by
midday. Breezy and relatively dry trade wind conditions are
expected from Saturday afternoon through the remainder of the
weekend, as strong high pressure remains anchored far north of the
state, with a dry and stable airmass in place over the islands.
Passing showers will favor windward and mauka areas, with only a
few light showers over leeward areas. The leeward slopes of the
Big Island will continue to see their usual diurnal pattern of
clearing skies late night and morning, with clouds and widely
scattered showers in the afternoons and evenings.

Little change is expected through the early part of next week,
with moderate to breezy trades prevailing, along with a typical
trade wind shower pattern. A wetter trade wind pattern may develop
by midweek, when models develop a mid level trough near or just
west of the state, and bring an area of enhanced moisture in from
the east.

&&

.AVIATION...
TEMPO MVFR conditions are likely in the overnight hours...mainly in
windward and mauka sections across the island chain...as an area of
showery low clouds moves in from the east-northeast. ISOL MVFR in
lower ceilings is also a possibility in leeward parts of the Big
Island...including the Kona airport...as daytime cloudiness
collapses and heads offshore.

An AIRMET for mountain obscuration is currently in effect for
Kauai.

&&

.MARINE...
Locally strong trade winds continue to affect portions of the
typically windier waters around Maui County as per current
land-based mesonet data, and a Small Craft Advisory remains in
effect for those areas through Saturday afternoon. Will take a
look at the late evening ASCAT pass and see if the waters south of
the Big Island need to be added to the advisory as well. Winds
will increase tonight across the northern half of the state,
namely around Kauai and Oahu, as a weak trough rides by. These
winds are expected to approach small craft advisory levels, and
these areas will need to be closely monitored throughout the next
24 hours.

Southerly swell continues to slowly decline in energy. A second
smaller, long period south swell is expected to arrive late
Sunday, bringing below advisory level surf through the middle of
the week. Elevated surf along windward facing shores will continue
due to short period trade wind swell. These surf heights are
expected to remain below advisory levels.

&&

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

&&

$$

DISCUSSION/MARINE...Jacobson
AVIATION...Kinel

Bulletins, Forecasts and Observations are courtesy of Honolulu National Weather Service Forecast Office