Area Forecast Discussion
Issued by NWS Honolulu, HI

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FXHW60 PHFO 250212
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
412 PM HST WED AUG 24 2016

.SYNOPSIS...
Very humid conditions with the chance for brief downpours will
remain into tonight. Tropical moisture will move west of the area
Thursday with drier trade winds moving in from the east. Breezy
trade winds are expected through the weekend with showers focused
over the windward slopes and mountains. Tropical moisture may
affect the islands again by the middle of next week.

&&

.DISCUSSION...
Humid conditions continue to plague the aloha state, but relief
is on the way in the form of drier trade winds. The trades will
push the tropical moisture west, with drier air reaching the Big
Island later this evening, Maui County and Oahu Thursday morning,
and finally reaching Kauai Thursday afternoon. Radar imagery as of
330pm shows limited convective showers around the smaller islands,
while portions of the leeward Big Island slopes have locally heavy
showers with isolated thunderstorms. Afternoon soundings show
atmospheric moisture has already dropped over Hilo with a
precipitable water value of 1.7 inches, from the overnight maximum
of 2.3 inches. With only the elevated heat source of the leeward
Big Island slopes able to generate heavy showers this afternoon,
widespread heavy rains are not expected and the flash flood watch
has been cancelled. However, the enhanced moisture lingering over
the state still brings the chance for locally heavy showers into
tonight.

A surface trough 600 miles west of Kauai will lift north tonight
allowing easterly trade winds to push back over the islands from
east to west through Thursday. Drier trade wind weather will
continue into early next week, as high pressure remains to our
north. Showers will focus over windward and mountain areas, while
leeward locations will see mostly clear skies. There is potential
for another round of humid weather by the middle of next week with
long term model guidance bringing tropical moisture close to the
state.

&&

.AVIATION...
Thunderstorms over the leeward slopes on the Big Island have
started to flare up this afternoon. CB tops on these storms are
mainly between FL350 and FL400. Elsewhere, activity has been
rather minimal this afternoon with scattered passing showers.
Cloud tops are generally between 10 and 15 thousand feet. However,
there is still a possibility for heavier showers and thunderstorms
to form in the next few hours under daytime heating. The leeward
Big Island slopes will start to see improvement later this
evening. AIRMET SIERRA for mountain obscuration is posted for
leeward Big Island.

A more easterly flow is expected to build back in tonight,
returning clouds and showers to favor windward areas. The
lingering enhanced moisture could still lead to periods of heavy
showers. AIRMET SIERRA will be tailored as needed. Most terminals
should remain VFR tonight with passing showers possibly
introducing periods MVFR. A drier airmass is expected to move over
the state as trade winds return.

&&

.MARINE...
High pressure will build well north of the state tonight, with
moderate to locally fresh trades returning to eastern islands
tonight, and into the western islands Thursday. As a result, small
craft conditions are expected to develop over the windier waters
around Maui and the Big Island Thursday, with winds remaining at
advisory levels through at least Thursday night and likely
continuing into the weekend. Short period trade wind swell will
increase surf a notch along eastern facing shores Friday and into
the weekend. Otherwise, no significant surf is expected.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
Small Craft Advisory from 6 AM Thursday to 6 AM HST Friday for
Maalaea Bay-Pailolo Channel-Alenuihaha Channel.

&&

$$

Morrison...Discussion and Marine
Eaton...Aviation



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