Area Forecast Discussion
Issued by NWS Honolulu, HI

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000
FXHW60 PHFO 241947
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
947 AM HST Wed Feb 24 2021

.SYNOPSIS...
Breezy to locally strong easterly trade winds will prevail
through the weekend, with clouds and showers favoring windward
and mountain locations. A modest increase in moisture moving in
from the east combined with an upper disturbance may lead to
better windward shower coverage Thursday night through the
weekend. A return of drier trade wind conditions will be possible
early next week.

&&

.DISCUSSION...
Breezy to locally strong trade winds will continue through the
weekend in response to strong high pressure (1040-1050 mb) far
northeast of the state. Clouds and showers will favor windward and
mountain locations, especially through the overnight and early
morning periods. Lowering upper heights combined with a slight
increase in moisture shifting into the area from the east will
support better windward shower coverage Thursday night through the
weekend. Although confidence remains low, this added instability
and better moisture source could trigger a thunderstorm or two
over the Big Island Friday into the weekend - mainly through the
afternoon periods across the leeward Big Island slopes. For the
smaller islands, expect some showers to spill over into leeward
locations due to a combination of the strong trades and the trade
wind inversion rising. A more typical trade wind pattern will be
possible beginning early next week, as drier air arrives from the
east.

&&

.AVIATION...
This morning, occasional MVFR cloud decks and mountain obscuration
have been noted on satellite imagery for Kauai, Maui, and the Big
Island. Airmet Sierra will continue for a couple more hours to
account for this, but improvement is expected by around midday as
most area airports return to VFR flight conditions this
afternoon. Drier trade wind weather is expected today, so any
isolated to scattered showers will favor north through east
sections of the islands throughout the period.

The main aviation concern throughout the period will be strong
easterly trade winds as a surface high northeast of the main
Hawaiian Islands strengthens overnight and tomorrow. This will
keep the threat of low-level mechanical turbulence throughout the
forecast period. As a result, Airmet Tango will remain in effect
for the entire state. Low-level wind shear concerns may also
return this afternoon, though confidence is not high enough to
include in the TAFs at this time.

&&

.MARINE...
Strengthening high pressure northeast of the state will produce
strong- to near gale-force easterly trade winds across most of
the Hawaiian waters. The exception will be over the Alenuihaha
Channel, where gales are expected through Thursday. Thus, a Gale
Warning is now in effect for the Alenuihaha Channel through
Thursday afternoon. A Small Craft Advisory is in effect for rest
of the coastal waters due to a combination of strong trades and
elevated seas. Strong trades and elevated seas will likely
continue through the weekend as another strong high builds far
north of the state on Sunday.

Strong trade winds over and upstream of the islands will keep
advisory level surf in place along east facing shores through the
first half of next week. A High Surf Advisory (HSA) is in effect for
east facing shores of Kauai, Oahu, Molokai, Maui and the Big
Island through 6 AM Monday morning. An uptick in surf is expected
over the next few days as the winds increase locally and upstream
of the state.

A series of small overlapping northwest swells will move through
the area into next week, with surf remaining below advisory levels
along exposed north and west facing shores. The first of the
series of northwest swells is expected late Thursday followed by
another reinforcing northwest swell late Saturday into Sunday.

Wrapping trade wind swell continues to provide some small surf
along south facing shores. A small out of season south swell will
give a boost to south shore surf late Thursday through Saturday.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
High Surf Advisory until 6 AM HST Monday for Kauai Windward-Oahu
Koolau-Olomana-Molokai Windward-Maui Windward West-Windward
Haleakala-South Big Island-Big Island North and East.

Wind Advisory until 6 PM HST Thursday for Molokai-Kahoolawe-Maui
Windward West-Maui Leeward West-Maui Central Valley-Windward
Haleakala-Leeward Haleakala-South Big Island-Big Island North
and East-Kohala-Big Island Interior.

Small Craft Advisory until 6 AM HST Friday for Kauai Northwest
Waters-Kauai Windward Waters-Kauai Leeward Waters-Kauai Channel-
Oahu Windward Waters-Oahu Leeward Waters-Kaiwi Channel-Maui
County Windward Waters-Maui County Leeward Waters-Maalaea Bay-
Pailolo Channel-Big Island Windward Waters-Big Island Leeward
Waters-Big Island Southeast Waters.

Gale Warning until 6 PM HST Thursday for Alenuihaha Channel.

&&

$$

DISCUSSION...Gibbs
AVIATION...Vaughan/Burke
MARINE...Kino


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