Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 739 PM EDT Mon Apr 7 2025 Valid 12Z Fri 11 Apr 2025 - 12Z Tue 15 Apr 2025 ...Gulf low pressure could lead to heavy precipitation for the southern coast and strong gap winds in the Alaska Peninsula this weekend/early next week... ...Overview... An upper low will be in place near the Bering Strait as the extended period begins Friday. Meanwhile an upper/surface low is forecast to track through the northern Pacific south of the Aleutians and Alaska Peninsula. These features should interact and combine into the weekend and early next week, albeit with model differences in exactly how. This pattern aloft will support surface low pressure in the Gulf, which could become reasonably deep early next week. Mean moist southerly flow near and east of the low could bring locally heavy precipitation to the southern coast of the Mainland into parts of the Panhandle, particularly over the weekend into Monday. Northerly to northwesterly gap winds may be brisk in the vicinity of the Alaska Peninsula behind this low over the weekend. ...Guidance/Predictability Assessment... Model guidance is finally in somewhat better agreement regarding the pattern late this week. After several days of GFS runs that centered an upper low north of Alaska over the Arctic, recent GFS runs are now in better alignment with the upper low center near the Bering Strait Friday. Meanwhile farther south, models are also reasonably agreeable in showing an upper low and associated surface low tracking west to east south of the Aleutians Friday and the Alaska Peninsula Saturday. Thus for the early part of the period, a multi-model blend of mainly deterministic models was able to be used. Over the weekend into early next week, there may be some complex evolution of the preexisting upper low near western Alaska with the shortwave trough to the south, with the possible added complication of Arctic energy diving south through the western Bering Sea. Models have a common theme of an upper low persisting but with more spread in its position. GFS runs center the upper low south in the Pacific Sunday-Tuesday, allowing for a deep surface low in the Gulf. Meanwhile the ECMWF and CMC keep the upper low farther north near Bristol Bay, and the ECMWF in particular then produced a deep surface low there around Monday, unlike other guidance. Ensemble means indicate troughing across both areas so it was difficult to determine if one model camp was better than the other. With individual models diverging, the forecast blend ramped up the proportion of ensemble means to around half Day 6 and more Day 7-8 to mitigate the differences. ...Weather/Hazards Highlights... Late this week, weak surface low pressure in the Gulf could focus coastal rain and inland/higher elevation snow over the far south and Panhandle, but with mainly light to moderate amounts. Some areas of lighter and more scattered precipitation (mostly snow) will extend farther north over the Mainland. Upstream, the upper low could spread light snow into the southwestern Mainland late week. Meanwhile, North Pacific low pressure tracking eastward likely just south of the Aleutians Friday and Alaska Peninsula Saturday will allow for increasing precipitation chances and breezy winds there. Combining energies aloft may lead to strengthening low pressure in the Gulf. With this deepening low, northerly to northwesterly winds on the backside could be brisk to strong across the Alaska Peninsula for the weekend and perhaps into next Monday. Additionally, this should provide support for more precipitation, with moderate to locally heavy amounts becoming more likely from the Kenai Peninsula into Southeast Alaska for the weekend into early next week. The details will continue to be refined in future forecasts. The upper low forecast to be over the western Mainland Friday will support below normal temperatures over the western half or so of the state. These below average temperatures should become more limited to the western coast with time, as milder than normal temperatures expand westward across much of the Mainland by early next week. Forecast highs in the Interior should generally be in the 40s to low 50s by Sunday and beyond. Southeast Alaska is forecast to see slightly below average temperatures late this week but warm slightly above normal, especially for lows, early next week. 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