Area Forecast Discussion Issued by NWS Honolulu, HI
000
FXHW60 PHFO 170239 CCA
AFDHFO
Area Forecast Discussion...CORRECTED
National Weather Service Honolulu HI
439 PM HST Sat Mar 16 2024
.SYNOPSIS...
Moisture along a front dissipating south of the state will
continue to bring showery weather to windward Big Island and Maui
tonight, while moderate northeasterly trade winds maintain
somewhat cool and slightly drier conditions over the rest of the
island chain. Moderate trade winds and a typical pattern of
windward rainfall will prevail early next week. Trade wind showers
may increase late Wednesday into Friday as a trough aloft passes
over the islands.
&&
.DISCUSSION...
A moderate and somewhat cool northeasterly trade wind flow
persists across Kauai and Oahu this afternoon, while lingering
moisture is maintaining wetter conditions over portions of Maui
County and the Big Island. The moisture is what remains from a
dissipating front, now located south and southeast of the Big
Island. While rainfall has been fairly unimpressive today,
generally less than a tenth of an inch, expect the northeast
trade winds produce continued light rainfall along windward Big
Island and Maui tonight, followed by a diminishing trend Sunday
morning. Showers will also linger over Kau and South Kona slopes
through the evening, then taper off late. From Molokai westward,
moderate northeast winds will maintain a cooler and drier air
mass tonight, with dew points in the upper 50s to around 60 and
limited moisture. Expect modest shower activity on windward slopes
of these islands and little rainfall leeward.
By Sunday afternoon, the front will dissipate to the south, and
trades will shift to a more typical east-northeast direction as
low-level ridging persists to the north of Kauai. Dew points will
hold in the lower 60s, and precipitable water will hover below an
inch, reflecting a somewhat dry air mass. Meanwhile, a mid-level
ridge will maintain stable conditions. As a result, expect modest
windward rainfall, and aside from a few afternoon showers on the
Kona slopes of the Big Island, leeward areas should be dry.
No significant changes are due early next week. The mid-level
ridge overhead will begin to erode Monday night and Tuesday as an
upper-level trough approaches from the west. Stable, moderate
trade winds will hold, focusing modest showers over windward
areas.
A gradual strengthening and destabilization of the trade wind
flow is possible Wednesday into Friday. Confidence is higher that
trades will likely build as a deeper surface high sets up far
north of the state, with breezy conditions possible by Friday. The
above mentioned upper-level trough will slowly pass over the
region during this time, bringing 500 mb temperatures as low as
-16C on Wednesday night and Thursday. While there could be some
increase in shower activity, a mid-level ridge may be able to
maintain stability and lower the chances of heavy rainfall.
&&
.AVIATION...
With increased moisture persisting across the eastern end of the
state, parts of Maui and the Big Island continue to be impacted by
periodic MVFR conditions due to clouds and showers. See AIRMET
Sierra below. Moderate to breezy northeast winds will increase
slightly heading into Sunday, and usher in drier air that will
help to gradually improve conditions across Maui and the Big
Island through the period.
AIRMET Sierra remains in effect for tempo mountain obscuration
above 2500 feet across north and eastern portions of Maui and the
Big Island. These conditions will gradually improving sometime
this evening.
&&
.MARINE...
A weak stationary front just southeast of the Big Island will
dissipate tonight. High pressure to the northwest of the islands
will build northwest of the state and gradually drift eastward,
resulting in moderate northeast winds through the remainder of
the weekend. An approaching front will pass north of the islands,
keeping moderate trades in place through the middle of next week.
Strong trades could return toward the end of next week, as a new
high builds north of the islands.
The current long-period northwest swell has come down
significantly today, enough that the High Surf Advisory has been
cancelled. A reinforcing northwest swell should arrive late
tonight, with surf along north and west facing shores returning to
near-advisory level late Sunday through early next week. Another
long-period northwest swell reinforcement may push surf up to
advisory levels Wednesday, before declining through the end of the
week.
South shore surf will remain tiny through the forecast period,
except for a slight boost Sunday through Tuesday as a new long-
period south swell moves through. East shore surf will also remain
small through early next week, with a slight increase possible
during the middle to latter part of the upcoming week as trades
increase over and upstream of the state.
&&
.HFO WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
DISCUSSION...Wroe
AVIATION...Farris
MARINE...TS