Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 718 PM EDT Tue Apr 23 2024 Valid 12Z Sat Apr 27 2024 - 12Z Wed May 01 2024 ...Overview... During this period an upper/surface low will drift east from the the Aleutians/Alaska Peninsula on Friday, across the Northeast Pacific ocean over the weekend into early next week before pushing into Southeast Alaska and British Columbia. North and east of this feature, upper ridging will stretch from Southeast Alaska northwest into the northern part of the state late week but erode with time. Another large trough upstream with one or two rounds of passing energy will track through the Bering Sea with a course toward the western Alaska coast; however there is a lot of uncertainty with the details of this feature. ...Guidance Evaluation and Preferences... Initially, the latest model runs have decent clustering with the upper low and upper ridge features particularly with the low undercutting the ridge over portions of eastern to northern Alaska. The trend for a steadier progression of the low eastward persists, therefore maintained continuity by utilizing a blend of the deterministic guidance favoring the 12Z ECMWF and GFS. Like previous runs, the model spread increases yielding low confidence for the forecast next week. By Sunday there is some uncertainty with how much energy may remain/come in near Bristol Bay. This makes the ECMWF (which has a ridge) out of phase with the CMC that lingers a small upper low there and the GFS runs that push additional energy in. Then a larger scale trough may push into the Bering and the Aleutians and western Alaska, but the timing is quite variable. Once again, the GFS solutions depict a faster progression bringing the trough east than the ECMWF and CMC and leads to more out of phase issues. The inclusion and weighting of the EC and GEFS ensemble means were quickly increased through the middle and latter periods, totaling to 60% percent by Wednesday. The means are pretty zonal due to the differences across the ensemble members but hopefully models will converge with time. ...Weather/Hazards Highlights... Gusty winds and precipitation will accompany the upper and surface lows late this week for portions of the Aleutians to Alaska Peninsula, into the southwest Mainland toward Kodiak Island and the Kenai Peninsula, with moderate amounts Friday lowering on Saturday. At this time the wind speeds will likely remain below the hazardous threshold. Some precipitation is likely over the weekend for Southeast Alaska as moist inflow increases ahead of the low moving east. Generally light amounts are forecast in northern parts of the Panhandle with more moderate amounts in southern parts. As another system approaches the Bering, Aleutians and western Alaska, precipitation chances will renew. The timing and location of this feature will determine where the heavier amounts will setup for the Aleutians, southwestern and south-central Alaska. Meanwhile the northern half of the Mainland can expect generally dry conditions. A majority of the state will have above normal temperatures through the end of the month with the highest anomalies likely positioned over the Interior. To the north of a front settling over the north-central mainland, cold high pressure over the Arctic may keep temperatures near to somewhat below normal, especially across the North Slope. Locations near the Southcentral coast and northern Panhandle may also see near or slightly below normal readings. Campbell/Tate 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