Hawaii Extended Forecast Discussion NWS Weather Prediction Center College Park MD 816 AM EDT Wed Mar 28 2018 Valid 00Z Thu Mar 29 2018 - 00Z Thu Apr 05 2018 By Thursday expect low level winds to become more easterly/southeasterly as the extreme southwest periphery of eastern Pacific high pressure builds over the islands. This wind regime should extend into the weekend. At least into Friday expect most shower activity to be on the lighter side with some degree of ridging aloft, though windward terrain of the Big Island may see a little enhancement. From the weekend into next week the primary forecast problem involves the southeastward extent of a slow moving surface front associated with a large central Pacific system, and corresponding axis of potentially heavy rainfall. Guidance continues to be split in terms of the amplitude of cyclonic flow aloft. The 00z/06z GFS and 00z UKMET/CMC/GEFS mean all suggest slightly greater amplitude/lower heights aloft relative to the 00z ECMWF/ECMWF mean/CMC mean, with the former scenario bringing more rainfall into the northwestern islands. However note from Monday onward the GEFS mean actually shows lower heights aloft than any other solution, so its southeastward extent of highest moisture and rainfall axis may be overdone. Continue to prefer an intermediate axis of moisture/rainfall between the GFS and ECMWF while awaiting a better clustering of guidance. Regardless of exactly where the front aligns during the weekend into early next week, there is reasonable model/ensemble agreement with upstream energy supporting the approach of another front with possible embedded waves by next Wednesday. Low level winds should turn more southwesterly and rainfall ahead of the front may reach the far northwestern islands by Wednesday. Rausch