Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 700 PM EDT Tue Sep 06 2022 Valid 12Z Sat Sep 10 2022 - 12Z Wed Sep 14 2022 ...Heavy rain threat for parts of the Panhandle and southern Alaska Monday-Wednesday... ...Pattern Overview and Guidance/Predictability Assessment... The 12z guidance suite for today shows overall good agreement on the large scale pattern the first half of the period which features a shortwave trough shifting through the Gulf on Saturday while an upper level low drops into the Bering Sea this weekend/early next week. The exception to this remains the GFS solution which displaces the Bering low farther to the north/east than the better consensus/ensemble means and is also faster with the next shortwave into the Gulf this weekend. After day 6, some of the more typical guidance errors regarding timing and strength of individual systems begins to creep in. The main outlier once again is the GFS showing a much stronger/deep closed low into the Gulf around next Tuesday (which has some support from the CMC as well). The ECMWF and the ensemble means suggest a little more modest of a solution which seems to be a good direction to lean at this point given the day 7-8 time frame. WPCs forecasts for today used a non-GFS consensus for days 4-6, quickly increasing usage of the ensemble means by 7-8. Some smaller amounts of the ECMWF was maintained through day 8 just for some added system definition. Generally, this maintains good continuity with the previous WPC forecast as well. ...Sensible Weather and Potential Hazards... The main emphasis of the forecast going into the weekend will be the evolution of shortwaves and embedded lows digging from the Bering to just south of the Aleutians, along with how they may interact with North Pacific flow/surface low pressure systems. Ongoing heavy rainfall across parts of the Panhandle to the eastern Kenai Peninsula should be waning by this weekend as the associated cold front exits into western Canada. However, another round of moderate to heavy rain is likely by early next week across the Southern Coast and northern Panhandle, with daily 1-2+ inch totals possible. Farther north, several inches of snow is likely for the higher terrain of the Brooks Range as moisture lifts northward ahead of a strong low pressure system in the Bering Sea, and moderate rain for the valley locations and western Alaska. Gusty winds and rough seas are also likely across the Aleutians and coastal areas as surface low pressure is maintained in the Bering Sea and cold fronts shift into the Gulf. Temperatures across the southern half of Alaska should remain near or below normal as clouds and precipitation dominate. A warming trend however looks to be on tap for the North Slope region and eastern Alaska. Santorelli Hazards: -Heavy rain across portions of the Alaska Panhandle into southern Alaska, Fri, Sep 9 and Mon-Tue, Sep 12-Sep 13. 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