Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 750 PM EDT Tue Apr 18 2023 Valid 12Z Sat Apr 22 2023 - 12Z Wed Apr 26 2023 ...A cold pattern returns this weekend into early next week especially across the eastern mainland... ...Overview... A blocky closed upper high to the northwest of Alaska will take multiple days to slowly lift northwestward farther away from the state. The overall flow will be redirected around this feature to the east and south for an Omega-style blocking pattern. Upper/surface low pressure in the Gulf of Alaska/northeastern Pacific as the period begins Saturday should get reinforced by a lobe of vorticity tracking south across the eastern mainland this weekend (leading to cold temperatures) to deepen in the Gulf by Monday. Then an upper low meandering near the Kamchatka Peninsula looks to send energy eastward near the Aleutians Monday-Wednesday with a surface low pressure system, leading to a bout of rain for the Aleutians and eventually the Alaska Peninsula. All this should continue a wet pattern at times for the southern coast. ...Guidance Evaluation/Predictability Assessment... Fortunately, recent guidance has come into better agreement with the pattern described above, after multiple days of showing blocky flow with the ridge northwest of Alaska but low confidence in the surrounding flow. 12Z models and ensembles all indicated low pressure redeveloping from the northeast Pacific into the Gulf of Alaska in response to the upper troughing extension diving south. A blend of the deterministic guidance favoring the GFS and ECMWF worked well for these features with the blending process serving to reduce individual model issues and provide a middle ground. Then, while there is general consensus for upper energy to track somewhere across the Bering Sea/Aleutians/northern Pacific through the first half of next week, there are some differences in timing and strength that affect the accompanying surface lows as well as variations with the interaction between this incoming energy and the preexisting Gulf energy. Some GEFS and EC ensemble mean components were added to the blend amid increasing uncertainty in the details of the overall pattern, but a majority deterministic blend was able to be maintained through the period for this issuance. ...Weather/Hazard Highlights... The lobe of energy/troughing moving across the eastern mainland this weekend will lead to chances of light precipitation there, but perhaps more notably, another shot of cold air. Expect well below average temperatures by 20-40F in between the Brooks and Alaska ranges, with cold air (though less anomalous) affecting the North Slope as well. Colder than average temperatures could make it all the way to the West Coast early next week as this trough overtakes the late week ridging. Temperatures should start to moderate gradually by midweek next week. The Panhandle may see below average temperatures in terms of highs but closer to normal for lows. Multiple developments of low pressure in the Gulf of Alaska/northeastern Pacific will support a wet and unsettled pattern across southeastern Alaska/the Panhandle this weekend into next week. Precipitation totals do not look terribly heavy on individual days but some moderate/enhanced totals are likely especially given the persistence of the precipitation adding up over time. Farther west, rain is likely to track east across the Aleutians this weekend and reaching the Alaska Peninsula early in the workweek with a low pressure/frontal system. This and some combination of energies from the east could spread precipitation into Southcentral Alaska around Monday-Wednesday. Tate Hazards: - Much below normal temperatures across portions of mainland Alaska, Sat-Tue, Apr 22-Apr 25. 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