Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 623 PM EDT Sat Oct 1 2022 Valid 12Z Wed Oct 5 2022 - 12Z Sun Oct 9 2022 ...Synoptic Overview... The extended forecast period begins on Wednesday with a deep closed low slowly sinking south across the Gulf and a narrow ridge axis extending across south-central Alaska, along with a shortwave trough crossing the northern half of the state. By the end of the week, a major storm system brushes past the northwestern coast, with the core of the storm expected to pass well to the northwest of the state. ...Guidance/Predictability Assessment... The 12Z model guidance suite depicts good overall synoptic scale agreement across the Alaska domain mid-week with the deep closed low slowly moving south over the Gulf, and a blocking ridge axis over northwest Canada. The ECMWF is stronger and slower with a lead shortwave trough crossing the mainland Wednesday into early Thursday compared to the model consensus. The CMC is likely displaced with a surface high over the eastern Gulf late in the week, whereas the model consensus supports this closer to the coast. A stronger disturbance approaching the Bering from Siberia is also reflected well in the guidance, although the CMC is bit more progressive and there is general agreement the core of the disturbance will pass well to the northwest of the state. By Saturday, the GFS remains much stronger with a trailing storm system over the Aleutians that has less in the way of ensemble support. Overall, a multi-deterministic model blend suffices as a starting point through Thursday, and then gradually increase the ensemble means going into next weekend to account for greater forecast uncertainty. ...Weather/Hazards Highlights... The broad low pressure situated over the Gulf should be close enough on Wednesday and Thursday to produce showers and mountain snow for coastal portions of southern Alaska and into the Panhandle region, before precipitation tapers off some in coverage to close out the week. For western Alaska, the potent disturbance approaching from Siberia will have a trailing cold front that should produce a band of light to moderate rain that will likely change to snow for the Brooks range and northwestern Alaska. Another surge of moisture is possible from the Kenai Peninsula to the St. Elias Mountains for the weekend as a new surface low may form along the front. In terms of temperatures, most of the state should enjoy readings above normal for early October, especially across the Interior with highs potentially running up to 20 degrees above normal. A modest cool down is likely behind the front across western Alaska later in the period, with readings returning closer to seasonal averages. Hamrick Additional 3-7 Day Hazard Information can be found on the WPC medium range hazards outlook chart at: https://www.wpc.ncep.noaa.gov/threats/threats.php 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