Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 732 PM EDT Wed Oct 30 2024 Valid 12Z Sun Nov 03 2024 - 12Z Thu Nov 07 2024 ...Deep low pressure system(s) could cause high winds across the Aleutians to Alaska Peninsula and enhanced precipitation in southern Alaska next week... ...Overview... Models continue to indicate a relatively broad and weak elongated upper low across the Bering Sea into the weekend. Shortwaves rounding the elongated low will provide support for a handful of weak surface lows, including atop the southwestern Mainland and the Gulf on Sunday, and models show a better signal today of one approaching Haida Gwaii by Monday as well. Meanwhile models continue to indicate that North Pacific surface lows are likely to consolidate and deepen Monday-Tuesday as the Bering upper low combines with energy stemming from current Typhoon Kong-rey and possibly Arctic energy quickly dropping south. The surface/upper lows look to move northeast and cross the Aleutians or western Alaska Peninsula and reach Bristol Bay or so by Tuesday or Wednesday, and perhaps get reinforced by another surface low. The deepening and then reloading upper troughing over the Bering Sea southward into the Aleutians and northern Pacific should promote ridging developing across the eastern Mainland to Panhandle after a mildly troughy pattern over the weekend. ...Guidance Evaluation/Preferences... As the medium range period begins Sunday, GFS/ECMWF/UKMET runs show surface low pressure in the Gulf, while the CMC focuses more on low pressure atop the Lower Kuskokwim region where other models have weaker low pressure. Then models are in somewhat better agreement for a low moving through the northeastern Pacific and strengthening as it moves toward Haida Gwaii Sunday-Monday, though still with some positional spread. GFS runs are generally in between the farther northeast 12Z EC and the west CMC and UKMET. The most impactful feature during the period will likely be a surface low that deepens as it moves northeast across the Aleutians/Alaska Peninsula causing high winds and enhanced precipitation. Features aloft consolidating to create upper troughing and support this surface low will be at least a piece of vorticity from what is currently Typhoon Kong-rey tracking northeast, the Bering upper low, and Arctic energy. On 12Z Monday/Day 5, there are likely to be two surface lows of note, one just south of the Aleutians and one to the west of that, and models vary on which one would become more dominant. ECMWF runs have been primarily strengthening the eastern low while the older 00Z and 06Z GFS runs favor the western one. The 12Z GFS depicted two surface lows in reasonable middle ground places for both, so that was favored for now while awaiting better model clustering. The NAEFS mean also depicted this (though could be right for the wrong reasons if some ensemble members favor each solution), as did the AIFS. Regardless, the lows seem to merge by Tuesday and the broadening surface low continues to deepen into the 940s or 950s. The surface low could move into the Lower Kuskokwim region or so into midweek, and potentially get reinforced by another surface low tracking east from Kamchatka by next Wednesday-Thursday. The 12Z GFS does not cluster well with other models for this secondary low as it is farther east/fast. The WPC forecast favored the 12Z GFS with lesser components of other models/means early in the period. Gradually transitioned away from the GFS and increased the ensemble means to just over half Day 7 and to 70 percent by Day 8 given the spread. ...Weather/Hazards Highlights... Winds should be weakening with low pressure in the Gulf of Alaska into Sunday, but some generally moderate precipitation could stream ahead of the low from Prince William Sound east into Southeast Alaska. Then the next surface low moving toward Haida Gwaii and vicinity could lead to locally heavy precipitation in the southern Panhandle early next week. Then the deep surface low moving from the northern Pacific northeastward is likely to cause high winds for the Aleutians and Alaska Peninsula by Monday-Tuesday. Strong winds may move into the Southwest Mainland depending on the eventual low track. Precipitation amounts will also increase once again from the Aleutians to Alaska Peninsula/southwest Mainland late Sunday-Monday to Southcentral on Tuesday and toward Southeast by next Wednesday-Thursday. Meanwhile, rounds of snow showers are possible farther north through the period. A tight pressure gradient across the North Slope could also cause some breezy easterly winds and blowing snow there. Most locations will see above average temperatures rising further into next week, with the possible exceptions of the Seward Peninsula, parts of the higher mountain peaks, and the Panhandle showing cooler temperatures early in the week. In most cases the anomalies for morning lows should be greater than anomalies for daytime highs. High temperatures will generally be in the upper teens to 20s in the Interior and North Slope, with 30s and low to mid 40s in southern areas. 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