Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 728 PM EDT Sun Mar 14 2021 Valid 12Z Thu Mar 18 2021 - 12Z Mon Mar 22 2021 ...Overview and Guidance/Uncertainty Assessment... The blocky pattern persists with the latest run of model guidance, at least for the first half of the extended forecast with the leading trough/low over the Gulf of Alaska, weak ridging behind it and a trough over western Bering Sea/eastern Siberia. Overall, there is decent clustering and agreement with the large scale setup with typical spread on specific details. These differences increase through the second half of the extended forecast, which decreases confidence on the timing, strength and location of features. A couple waves of low pressure are expected to lift toward the Southeast coast and along southern mainland early in the period, then with some ridging expected to develop aloft for day 6-8 over western mainland Alaska. For this issuance the preferred WPC blend began with equal parts of the 12Z ECWMF/GFS/UKMET and shifted to a steady increase of the GEFS mean and the ECWMF ensemble means for days 6 and beyond. ...Weather/Hazards Highlights... With the waves of low pressure approaching the southern Mainland and the Southeast, these areas could have periods of scattered to widespread precipitation. A majority of the Mainland with be mostly quiet and dry. The Aleutians could also have several rounds of precipitation. Most of the region will have temperatures near seasonal average, or slightly below average through the extended period. The North Slope is forecast to have temperatures warmer than seasonal average. Campbell No significant hazards are expected over Alaska during this forecast period. 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