Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 329 PM EDT Fri May 17 2019 Valid 12Z Tue May 21 2019 - 12Z Sat May 25 2019 Models present chaotic and disparate solutions in terms of the pattern across Alaska during the extended forecast period. An upper-level mean trough is expected to be in place on Wed near/south of the western Aleutians, with shortwave energy traversing southwesterly flow on the east side of the trough into the Gulf of Alaska and a mainland Alaska. Timing differences exist even early in the period with respect to these smaller-scale waves. Through time, differences only amplify. Major differences emerge by the middle of next week as to whether upper riding builds north across the Gulf toward mainland Alaska (a scenario the ECMWF has fairly consistently shown), or ridging that remains weaker allowing the upper mean trough to slide east toward the Gulf (as shown by the GFS). The CMC has waffled between the two scenarios, while ensemble means seem to provide somewhat more support toward the ECMWF idea, which is also consistent with forecast continuity. Thus, a blend of the ECMWF with ECENS/NAEFS ensemble means was used as a forecast starting point on day 4 (Tue), with majority ensemble means from day 5 (Wed) onward. This solutions depicts a slow-moving low pressure system south of the Aleutians Wed-Thu, and nearing the island chain by Fri-Sat. Confidence is low in the specifics of this forecast, however. 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