Hawaii Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
829 AM EDT Wed May 02 2018

Valid 00Z Thu May 03 2018 - 00Z Thu May 10 2018

...Locally heavy rain possible over the western islands...

A moisture plume associated with the dying/former front just to
the southeast of the Big Island is currently moving back to the
northwest through the islands as an upper low near 31N/167W is
moving eastward. This moisture axis will linger over the NW
islands over the next few days where flash flooding may be an
issue with persistent/training rain/convection with LIs around
zero to -2. Global/hi-res models and ensembles indicate some
potential for locally heavy rains, also shown per the 00Z GEFS
reforecast QPF "MAX" values (relative to similar forecasts)
Thu-Fri. The upper trough should move through by Friday, shifting
the less intense moisture axis southeastward until another
boundary to the NW moves through on Sunday to finally bring in
drier air to most of the state. A 1030mb high will slide eastward
along 33N next week, keeping higher PWs along/south of 20N. Shower
activity should then be limited to windward locations next week
with local enhancements via brisk northeast trades.


Fracasso