435 
FXHW60 PHFO 191944
AFDHFO

Area Forecast Discussion
National Weather Service Honolulu HI
944 AM HST Thu May 19 2022

.SYNOPSIS...
Moisture along a weakening front will maintain higher shower 
chances for Kauai through tomorrow, with flooding rainfall and 
thunderstorms possible this afternoon. The rest of the state will 
experience mainly spotty afternoon showers under decreasing 
southeast to south winds. Layered clouds will gradually diminish 
today as humid conditions persist through Friday. Moderate trade 
winds will build during the weekend and will hold into next week.

&&

.DISCUSSION...
Humid southerly winds will produce areas of heavy showers today,
especially around Kauai, while layered mid to high clouds thin.
Active showers persist along a stalled front just northwest of 
Kauai, though little rainfall is occurring from Oahu to the Big 
Island this morning. The strong upper level trough that brought 
stratiform rainfall to mainly Kauai and Oahu yesterday is pushing 
east of the state this morning. Mid to high clouds will slowly 
thin, but conditions will remain somewhat unstable as the upper 
trough slowly departs. As a result, expect low clouds and spotty 
heavy showers to develop over the islands this afternoon, 
especially around Kauai where a Flash Flood Watch remains in 
effect due to the proximity of the lingering deep moisture. There 
could be areas of gusty south winds to the north of terrain on 
Kauai and Oahu today, but as winds decline this afternoon, sea 
breezes should dominate over most areas. With dew points hovering 
in the lower 70s, humidity will remain high.

Tonight and Friday, a humid land and sea breeze regime will 
prevail from Oahu to the Big Island, while a band of moisture 
along the dissipated front stalls over Kauai. Upper level ridging
will be slowly building, but a lingering mid level trough will
maintain some instability. As a result, expect clouds and spotty
showers, some briefly heavy, to develop over most islands in the
afternoon and diminish during the overnight hours. Cloud cover 
and shower chances will remain highest over Kauai. There does not
appear to much of a flood threat on Kauai tonight and Friday 
morning, but heavier rainfall possible Friday afternoon could lead
to short term flooding concerns.

An increasingly stable trade wind flow will build during the
weekend. High pressure far northeast of the state will strengthen,
causing trade winds to slowly increase and push the deeper 
moisture west of the state. A mid level ridge will also build 
overhead and bring increased stability. The result will be a
return to typical trade wind weather that will hold into next
week.

&&

.AVIATION...
A broad field of gentle background ascent within the established 
moist southerly flow regime will result in periodic low clouds 
and showers focusing over leeward zones. A few showers may be 
locally heavy, mainly near Kauai which is located within the 
eastern edge of the deepest moisture. Likewise, Kauai will 
experience a greater frequency of MVFR through the forecast 
period. Showers will further increase over Kauai tonight as a 
remnant front approaches from the west.

AIRMET Sierra for mountain obscuration is in effect for Kauai &
Lanai, and will likely remain in effect for Kauai through tonight.

Light icing is possible within the 14.5-25kft mid/upper cloud
layer.

&&

.MARINE...
Strong southerly winds will continue over Kauai waters today as 
a slow moving cold front stalls just west of Kauai. The southerly
winds and a long period south swell are producing rough seas over
southern leeward waters near Kauai and Niihau that are normally 
protected during a typical trade wind weather pattern. A Small 
Craft Advisory (SCA) remains in effect for all waters around Kauai
through this afternoon. Expect locally higher winds and seas near
heavy showers and thunderstorms. The front is expected to weaken 
as it lifts northward later this evening with a sharp drop in 
southerly winds by tonight. High pressure will begin to build back
over the region Friday with easterly trade winds strengthening 
from east to west across the area this weekend. SCA conditions 
will likely return to the typical windier waters and channels 
around Maui County and the Big Island as this happens.

Surf heights along south facing shores will remain elevated into 
the weekend as the current south swell becomes reinforced today. 
In the long range, models show quite a bit of activity in the 
southern hemisphere, which could translate to a few south shore 
surf events over the next week or so. 

Surf along north and west facing shores will trend up today as a 
small, medium-period northwest (300-320 degrees) swell arrives. A 
return to small, summer-like conditions is expected over the 
weekend and into the first half of next week as this swell energy
fades.

&&

.HFO WATCHES/WARNINGS/ADVISORIES...
Flood Watch until 6 PM HST this evening for Niihau-Kauai-

Small Craft Advisory until 6 PM HST this evening for Kauai 
Northwest Waters-Kauai Windward Waters-Kauai Leeward Waters-
Kauai Channel.

&&

$$

DISCUSSION...Wroe
AVIATION...JVC
MARINE...TS