Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 751 PM EDT Sat Apr 01 2023 Valid 12Z Wed Apr 05 2023 - 12Z Sun Apr 09 2023 ...Overview... Overall an upper troughing pattern is likely across much of Alaska through the latter half of next week into next weekend with various shortwave and longwave troughs producing it. Meanwhile rounds of low pressure in the Gulf of Alaska should lead to a wet pattern for southeast Alaska. ...Guidance Evaluation/Predictability Assessment... Model guidance appears fairly agreeable on the large scale but with some small scale differences certainly within typical spread at the medium range lead time. The period starts Wednesday with an upper low north of Alaska (that remains there through much of the week) producing troughing across the mainland while another shortwave moves across Southcentral Alaska and helps produce a Gulf of Alaska surface low. For Thursday-Friday, another upper low shifts southeastward across the Bering Sea and Aleutians, while a northern Pacific low shifts east and northeast toward the Gulf of Alaska. The main outlier that appeared in the 12Z model guidance was with the latter feature, as the 12Z GFS/GEFS suite was farther east/more progressive than the non-NCEP guidance and the previous GFS. Other than that, models show general agreement that energy from those features should merge and produce a northern-Pacific-centered upper low over the weekend. The WPC forecast was based on a blend of the 06Z GFS (given the differences noted in the 12Z GFS) and the 12Z ECMWF/UKMET/CMC, with introduction of the ensemble means with time and increasing their proportion to almost half by day 8. ...Weather/Hazard Highlights... Multiple rounds of precipitation are likely especially across the Panhandle and back into Southcentral Alaska as surface lows and deep layer southwesterly Pacific flow direct moisture into the region. There may be some potential for flooding if there are multiple days with heavy amounts in the same area and/or rain falling on areas with snowpack and rising dewpoints promoting quick snowmelt, but this remains uncertain. Snow is possible farther inland across the mainland particularly Wednesday and perhaps into the latter part of the week. Meanwhile the Aleutians has a chance of light precipitation around Thursday/Friday as a low passes over, with some threat of windy conditions too. Moderate to strong winds are possible on the backside of the Gulf lows with possibly some gap winds in favored areas from the Aleutians east to the Kenai Peninsula depending on the low tracks. The trough aloft will keep temperatures near to below normal in terms of highs through the period, though lows could stay warmer than normal across the Panhandle and southeastern parts of the mainland with the mild moist inflow. Tate 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