Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 540 PM EST Thu Dec 05 2019 Valid 12Z Mon Dec 09 2019 - 12Z Fri Dec 13 2019 ...Heavy precipitation expected across southern mainland Alaska... Multi-low pattern will be present over the high latitudes to start the week next week before settling into a deeper, singular system in the Gulf next Wednesday. Models and ensembles were in decent agreement with a few exceptions for the first few days of the forecast. The 12Z Canadian was most displaced from the otherwise good clustering of the 12Z GFS/ECMWF/UKMET for the lead low moving through Bristol Bay and its attendant cold front to the south-southeast (providing the moisture pathway from the mid-latitudes and subtropics for significant rain/snow next Sun-Tue). Areal extent may be focused, but ensembles suggest precipitable water anomalies in the +2 to +2.5 sigma range and QPF over 5" along southeastern Kenai and on the west side of Cook Inlet. To the southwest, a pair of systems south of the Aleutians will morph into a more coherent system by late Tue into Wed. Ridging to the northeast will hold tight through the end of the week, allowing/forcing the Gulf parent low to linger and slowly dissipate as its front pushes past the Panhandle. Trended toward the ensembles with some details added from the GFS/ECMWF as they tracked the low in opposite directions with the ensembles in between. Next system will enter the western Bering late in the week. Fracasso 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 Hazards: - Heavy precipitation across portions of southern Alaska, Sun-Tue, Dec 8-Dec 10. - High significant wave heights for coastal portions of mainland Alaska, Sun, Dec 8. 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