Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 728 PM EDT Fri Apr 5 2024 Valid 12Z Tue Apr 9 2024 - 12Z Sat Apr 13 2024 ...Synoptic Overview... A surface low is forecast to encompass much of the northern Gulf region going into the middle of the work week, with an arctic trough reinforcing this low and giving it some staying power through late Wednesday. Much colder temperatures arrive for the western half of the mainland to begin the week behind a strong cold front that will be aided by the arctic upper trough, followed by a steady moderating trend through the end of the week. Periods of rain and mountain snow are expected for the southern coastal areas owing to onshore flow. The next organized storm system crosses the Bering Sea mid to late week with increasing winds and rain for the Aleutians. ...Guidance Evaluation and Preferences... The 12Z model guidance suite has a good overall depiction of the synoptic scale pattern on Tuesday across the Alaska domain with only minor mesoscale differences noted, so a multi-deterministic model blend works well as a starting point in the forecast process. There is more model spread with the next incoming storm system across the Bering during the Wednesday-Thursday time period, with the GFS continuing to depict a stronger triple point low south of the Aleutians. Model spread increases substantially by next Friday and Saturday with shortwave energy pivoting around the southern periphery of the main Bering Sea low, with ensemble means increasing to about 50-60% of the forecast blend by that time. ...Weather/Hazards Highlights... The low pressure system over the Gulf through Wednesday will result in moist Pacific onshore flow for precipitation from the Kenai Peninsula to Southeast Alaska. While amounts are not forecast to be all that heavy on any particular day (no atmospheric river events anticipated), rain and snow totals will add up with multiple days of moderate rain/snow through next week, generally on the order of 1 to 3 inches of QPF. On the backside of the Gulf low, northwesterly gap winds could be strong for the Alaska Peninsula to Kodiak Island and to the western Kenai Peninsula and surrounding waters, likely peaking in strength on Monday into Monday night. For the Monday-Tuesday time period, a pronounced cooling trend is likely for much of the western and northern mainland, with anomalies of 15-25 degrees below normal going into Tuesday. This equates to subzero overnight low temperatures for the normally colder locations of the western Interior, and highs in the 0s over the North Slope and 10s for the western Interior. Gradual moderation closer to normal is forecast for midweek and beyond, possibly reaching above average for many areas by next weekend. Southeast Alaska should see near average lows but persistent below normal highs next week given the increased cloud cover and precipitation. Hamrick 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