Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 259 PM EDT Thu Jun 14 2018 Valid 12Z Mon Jun 18 2018 - 12Z Fri Jun 22 2018 ...Heavy rainfall for Southwest/Southern Alaskan and Panhandle up into the interior... ...Guidance Assessment and Weather Highlights... Models and ensembles agree with synoptic scale depiction of an anomalously amplified flow pattern over Alaska and vicinity for the next week. This lingering pattern is highlighted aloft by a moisture/precipitation laden closed mean trough anchoring over the southeastern Bering Sea and potent ridging spread from western Canada to the eastern Alaskan interior. A series of low pressure systems are slated to lift poleward on the western peripherty of the ridge, with a lead system including the moist extratropical remains of former western Pacific tropical storm Maliksi. While the smaller scale specifics of this low train and flow interactions remain quite unclear, it is very likely that deep layered moisture feeding inland into southwest and southern/southestern Alaska downstream will fuel widespread and terrain enhanced heavy precipitation onshore, with lessening but locally enhanced activity working into the west-central interior. Mid-upper level arctic mean troughing prominent overtop to the north of the state offers less predictability, but guidance overall shows the feature and cooling/unsettling effects through northern Alaska weakens and ejects into midweek. The WPC Alaskan product suite was mainly derived from a composite blend of the 12 UTC GFS/GEFS mean and 00 UTC ECMWF/ECMWF ensemble mean. Applied higher weighting to the deterministic models days 4/5 (Monday/Tuesday) and transitioned emphasis Wednesday onward toward the ensemble means amid growing forecast spread. Schichtel WPC medium range Alaskan products including 500mb, surface fronts/pressures progs and sensible weather grids can be found at: http://www.wpc.ncep.noaa.gov/alaska/ak_5dayfcst500_wbg.gif www.wpc.ncep.noaa.gov/alaska/akmedr.shtml http://www.wpc.ncep.noaa.gov/alaska/ak_5km_gridsbody.html