Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 659 PM EDT Thu Sep 28 2023 Valid 12Z Mon Oct 02 2023 - 12Z Fri Oct 06 2023 ...Parts of Southern and Southeast Alaska to remain generally unsettled through next week... ...Pattern Overview and Guidance Evaluation/Preferences... The period begins Monday with shortwave energy moving into the Gulf of Alaska, as additional waves of energy rotate through western/southern Alaska around a meandering Arctic upper low into the middle of the week. Latest 12z guidance for today shows some uncertainties in the details/timing of these shortwaves, but a general model blend (weighted towards the ECMWF) seemed to provide a good starting point for the day 4-6 forecast. After this, uncertainty grows regarding a couple of upper lows, one towards the Aleutians and another initially well south of Alaska, and eventual late period interaction/phasing as a blocky upper ridge builds into the Gulf and Southeast Alaska. Models suggest this blocky ridge should force the upper low over the northern Pacific northward, possibly bringing a modest cyclone towards the Alaska Peninsula/Southern Coast region late next week. Given the growing uncertainty, the days 7 and 8 WPC forecast relied heavily on the ensemble means, with the ECMWF which was the deterministic solution closest to the ensemble means and could provide a little extra detail and system definition. ...Pattern Overview and Weather/Hazards Highlights... A deepened Pacific Storm this weekend in the Gulf will push inland by Monday, but a renewed surge of energy in its wake across the Gulf will continue a threat for at least locally heavy rains across parts of Southeast Alaska through Monday. This cold frontal surge, aided by northern stream flow, should allow for gusty gap winds through Southcentral Alaska and vicinity. Rainfall should become lighter and more showery during the middle of next week but still generally unsettled along the coast as general troughing remains over the region. Elsewhere, Mainland Alaska should stay relatively quiet/showery as precipitation chances increase from west to east across the Aleutians ahead of an upper low moving into the region. Another surface low which lifts towards the Alaska Peninsula region late in the week could bring another round of potentially heavy rainfall to parts of southern Alaska, but there is still a great deal of uncertainty on this setup. Temperatures across Alaska should trend cooler with time, with the greatest anomalies across Southern/Southeast Alaska and the Brooks Range. The North Slope, especially closer to the coast, should stay near or above normal during the period. The far southern Panhandle region may trend warmer by later in the week as upper ridging builds over the region. Santorelli Hazards: - Heavy rain across portions of the Alaska Panhandle and mainland Alaska, Sun-Mon, Oct 1-Oct 2. 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