Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 727 PM EDT Sat Jul 08 2023 Valid 12Z Wed Jul 12 2023 - 12Z Sun Jul 16 2023 ...Overview... A stacked low pressure system is forecast to meander around the northern Pacific for the latter half of next week into the weekend, and the initial surge of moisture with this system should lead to some moderate rain amounts around the southeastern quadrant of the Mainland Wednesday-Thursday. Farther north, the upper-level flow should be a little more progressive, with a ridge over the Aleutians and Bering Sea midweek before pushing east while likely weakening somewhat, as energy/troughing from the Kamchatka Peninsula presses eastward into the Bering. The strength of the ridge remaining over the Interior will help determine how much temperatures could warm there, but some areas may potentially see highs in the 80s. ...Guidance Evaluation/Preferences and Predictability Assessment... Most model guidance is in relatively good agreement through much of next week with the pattern described above, with the exception of the CMC. While there could be some relatively small-scale troughing atop the North Slope on Wednesday-Thursday, the CMC took energy from there southward and lingered a somewhat potent upper low over the Interior that refuses to weaken. Given that other models direct energy elsewhere and show higher heights than the CMC, a blend of the 06/12Z GFS and 12Z ECMWF and UKMET was favored instead for the early part of the forecast. As troughing comes closer to the state across Siberia and the Bering Sea by late week, some notable model differences do start to arise with its timing, while farther east across the Arctic, the largest model differences appear. The 12Z GFS was particularly strong with ridging over northeastern Alaska into the Arctic, while the 06Z GFS and 12Z ECMWF indicate more troughing northeast of the state, not allowing for as strong of ridging to take hold. The latter solution was more similar to the ensemble means, so the 12Z GFS solution seemed suspect at this point. There are also some typical wiggles with the positions of the northern Pacific low between models. Given the increasing spread, decreased particularly the GFS runs in the forecast, and increased the proportion of ensemble means through the period to about half Day 7 and just over half Day 8 since the means were in relatively good agreement compared to the individual models. ...Weather/Hazards Highlights... Low pressure over the northern Pacific/Gulf of Alaska will allow for some precipitation to affect Southcentral into the Copper River Basin and northward on Wednesday-Thursday. Rainfall amounts do not look to be too heavy but could be relatively enhanced over the southern Kenai Peninsula and the Alaska Range. A swath of moisture ahead of the upper trough and a cold front could bring some rain chances to the Aleutians and western Alaska Thursday-Friday and into the Alaska Peninsula Friday-Saturday. Meanwhile, weak but persistent low pressure in the northeast Pacific may lead to showers over the Alaska Range most days through next weekend, likely following a diurnal pattern. Temperatures at the start of the forecast period Wednesday are likely to be a mix of above and below normal without too much in terms of significant anomalies. The southeastern Mainland may be generally below average for highs given the rain potential. But into late week, the potential ridgy pattern may help create warmer than average temperatures across much of the state, with widespread above normal lows and likely warm highs as well, tracking west to east with time. Model guidance varies on how warm temperatures could get dependent on the strength of the ridge, but a middle ground forecast currently shows temperatures in the 70s to low 80s across the Interior by late week into the weekend. 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