Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 600 PM EDT Wed May 15 2024 Valid 12Z Sun May 19 2024 - 12Z Thu May 23 2024 ...Heavy rainfall/runoff threat for Kodiak Island and SouthCentral Alaska Saturday... ...Guidance Evaluation and Preferences... 12 UTC GFS/ECMWF/UKMET/Canadian model pattern solutions still offer less than stellar run to run continuity through medium range time scales. A composite seems reasonable for this weekend, but forecast spread increases thereafter. Opted to switch preference to still compatible 12 UTC GEFS/ECMWF/Canadian ensemble means for next week amid growing uncertainty. Of the models, the 12 UTC GFS/ECMWF are in better larger scale pattern evolution agreement with the GEFS/ECMWF/Canadian ensemble means next week to venture for details. ...Overview and Weather/Hazards Highlights... The southeastward digging of an amplified Arctic stream upper trough and surface low/frontal system through the Bering Sea and Southwest Alaska/southern Interior to the northern Gulf of Alaska remains highlighted for this weekend. This should spread a swath of enhanced winds and moderate rains across the broad region and into Southeast Alaska before exiting Monday. The greatest risk of heavier rainfall and associated runoff issues may be Saturday/Saturday night for Kodiak Island and SouthCentral, so a collaborated threat area is depicted on the WPC Hazards Outlook chart linked below along with additional supporting WPC products. The weather pattern remains unsettled into Monday over the Mainland as upper ridging is temporarily eroded before rebounding for through next midweek to renew warmth. However, it is a system to monitor as an outlier 12 UTC Canadian model does not support the rebounding of this ridge in a more progressive flow regime. Meanwhile in most guidance, amplified upper trough and associated and organized surface lows/frontal systems with some enhanced winds/waves/rains remain slated to work across the northern Pacific, Aleutians, the Bering Sea and toward Southwest Alaska early next week. There is some opportunity for the subsequent transfering of ample energy downstream into the Gulf of Alaska into/through next midweek to monitor for growing predictability and hazardous focus for the Alaskan southern tier. Schichtel 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