Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 730 PM EDT Wed Jun 02 2021 Valid 12Z Sun Jun 06 2021 - 12Z Thu Jun 10 2021 ...Overview and Guidance Evaluation... A deep upper-level low is forecast to be located between northwestern Alaska and Siberia at the start of the medium-range period later this weekend. The ECMWF and CMC led the trend yesterday to dig this upper low southeastward down the West Coast early next week toward the Gulf of Alaska. There has been increasing support from the ensemble means for this scenario since yesterday. The GFS has also joined this camp but with considerable run-to-run variability with the forward speed of this upper low. A general model compromise was used to derive the WPC Alaska medium-range grids. This blend included the 12Z GFS/GEFS, 12Z CMC/CMC mean, and the 12Z ECMWF/00Z & 12Z EC mean, trending toward the ensemble means for Days 7-8. With a general model compromise, the upper low is allowed to slide southeastward across western and southwestern Alaska into the Gulf of Alaska through early next week. Elsewhere, upper troughing and a surface front appear to linger south of the western Aleutians as weakening impulses push northward toward the area from the northern Pacific. ...Weather/Threats Highlights... Lingering precipitation across the Alaska Panhandle and in the vicinity of the Tanana River Valley in southeastern Alaska is forecast to gradually taper off this Sunday. Meanwhile, increasing chance of rain can be expected to reach western Alaska on Sunday before overspreading southwestern Alaska and the Alaska Peninsula on Monday and Tuesday due to the passage of the upper low. Some diurnal rain showers could linger across the interior mountain ranges into midweek. Across the Aleutians, rain chances should increase gradually through the middle of next week as moisture from the south arrives ahead of a lingering frontal system across the far northern Pacific. Temperatures are expected to be cooler than normal for southwestern Alaska on Sunday due to clouds and precipitation but they should return to slightly above normal level early to middle next week. Temperatures for the remainder of Alaska should not stray too far from normal while a slow warming trend sets in. Much of the interior sections should see highs reaching into the 70s but only into the 40s near the coast of the North Slope. Kong 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 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