Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 320 PM EDT Tue Jun 04 2019 Valid 12Z Sat Jun 08 2019 - 12Z Wed Jun 12 2019 The large scale pattern across Alaska and the North Pacific is expected to remain relatively stable through the extended forecast period. Ensembles show consensus that positive height anomalies should persist across the Bering Sea through the middle of next week. Upper ridging is also expected to become reestablished across western Canada, with an axis of positive height anomalies extending north/west across mainland Alaska to the Bering upper high. This setup will keep the predominant storm track/strongest upper jet suppressed to the south of Alaska and perhaps just south of the Aleutians. Models showed significant detail differences despite overall good large scale agreement. Shortwave energy traversing the strong North Pacific upper jet was one point of contention. The ECMWF was not favored in this area as it seemed to over amplify upper shortwave energy passing south of the Aleutians Sat-Sun, in between the two larger scale troughs (one across eastern Russia and another approaching the Gulf of Alaska). The GFS kept flatter flow or even slightly anticyclonic flow in this area, which made more sense conceptually. The solution across this area has downstream implications on the timing of a low pressure system expected to move into the Gulf of Alaska early next week (the ECMWF was much faster with this feature due to its somewhat less blocky flow at 500 hPa). Farther north, the ECMWF was generally weaker than consensus with the upper ridge axis across interior Alaska, which would allow more arctic shortwave energy to dig south into the interior than the GFS (and CMC) which keep a stronger ridge in place with less potential for energy from higher latitudes to move south. There was some consensus evident by the end of the period that an upper low should potentially approach the western Aleutians, with the potential for an associated relatively deep surface low. Despite broad consensus on this feature, detail differences were quite large on the timing, track, and intensity of such a system, and thus a consensus/ensemble approach was preferred. Given these considerations, the GFS was favored among the deterministic guidance, and was used heavily during days 4-5 (Sat-Sun), with a shift to majority GEFS/NAEFS ensemble mean weighting for days 6-8. Ryan Additional 3-7 Day Hazard information can be found on the WPC medium range hazards chart at: https://www.wpc.ncep.noaa.gov/threats/threats.php - No significant hazards are expected over Alaska during this forecast period. WPC medium range Alaskan products including 500mb, surface fronts/pressures progs and sensible weather grids can also be found at: https://www.wpc.ncep.noaa.gov/alaska/ak_5dayfcst500_wbg.gif https://www.wpc.ncep.noaa.gov/alaska/akmedr.shtml https://www.wpc.ncep.noaa.gov/alaska/ak_5km_gridsbody.html