Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
343 AM EDT Thu May 18 2023

Valid 00Z Fri May 19 2023 - 00Z Fri May 26 2023

A wet pattern is in store for Hawaii for the latter part of this
week as an upper trough moves across the state. Anomalously high
tropical moisture will stream in with the deep southerly flow
with/ahead of this feature, providing for widespread rain. Some
thunderstorms may be possible as the trough aloft could lessen or
or eliminate the typical inversion and provide instability, but a
limiting factor for strong storms could be the widespread cloud
cover reducing surface heating. Regardless enhanced rainfall
totals are likely across especially the western islands
Thursday-Friday, where the local Weather Forecast Office has a
Flood Watch in place, as Kauai/Oahu are likely to see the best
combination of moisture and dynamical support for heavy rain.
Showers with potentially heavy rain rates can still be expected
for the eastern part of the state though.

Shower coverage should gradually decrease through the weekend as
the weakening upper trough moves away and is replaced by an upper
ridge. This will shift the moisture plume west of the state next
week while surface highs build to the northeast and eventually the
northwest too, creating a more typical and drier easterly trade
wind pattern. Trades may increase to breezy levels at times next
week, and showers that do form should focus across windward and
mountain areas.

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