Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 658 PM EST Sun Nov 03 2024 Valid 12Z Thu Nov 07 2024 - 12Z Mon Nov 11 2024 ...Active pattern featuring multiple northeastern Pacific low pressure systems will bring periods of heavy precipitation and gusty winds to the Aleutians, southern coast, and Southeast late this week/weekend... ...Overview... A deep and broad upper low will position itself over the eastern Bering Sea and vicinity midweek, consolidating surface low pressure aided in part by the remnants of TC Kong-Rey from the western Pacific. Impacts from this system and an additional system over the northeastern Pacific passing along to the south and into the Gulf of Alaska will linger into the late week, with heavy precipitation across southwest Alaska, the southern coast, and into Southeast Alaska where flooding is possible. Additional energy and surface low pressure systems are expected to move eastward through the northeastern Pacific bringing periods of precipitation and gusty winds along the Aleutians, southern Coast, and Southeast Alaska this weekend and early next week as an active storm track remains in place. Meanwhile, a tight surface pressure gradient could cause strong easterly winds across the North Slope with some blowing snow, but precipitation chances otherwise should remain very scattered across the Interior/North Slope. ...Guidance Evaluation/Preferences... Overall the latest model guidance is in reasonably good agreement featuring a progressive, active period in the northeast Pacific into the Gulf of Alaska with a parade of multiple, potentially deep low pressure systems. A deepening/consolidating low pressure system connected in part to the remnants of TC Kong-Rey will pass over the Aleutians early next week and bottom out on Tuesday as it moves into the Bering Sea. The system will weaken but remain as an area of low pressure in the vicinity into the start of the forecast period (Thursday Nov 4 - Monday Nov 11). A steady area of high pressure over the Arctic will keep activity to the south, with multiple systems expected to track northeastward from the Pacific along/south of the Aleutians and into the Gulf of Alaska on the southern side of the mean troughing/low pressure over the Bering Sea. The deterministic models were well clustered with an initial system moving into the Gulf of Alaska Thursday, allowing for a composite model blend to start the period. Upstream another system approaches the Aleutians Friday with good clustering of the 12Z ECMWF/GFS/CMC allowing for another composite blend without the UKMET. The GFS brings this system east faster, south of the the Alaska Peninsula by Saturday, while the ECMWF/CMC and ensemble means remain a bit further west, with the updated forecast emphasizing the better clustered ECMWF/CMC during this time frame. The guidance clusters well again as the system moves into the Gulf Sunday with yet another system upstream south of the Aleutians. The GFS/ECMWF begin to diverge a bit in placement but not on strength with the next upstream system, indicating yet another potentially deep low, while the CMC is much weaker. An eastward track of the system south of the Aleutians is relatively well agreed upon in the GFS/ECMWF given the increasing forecast lead time by next Monday, both indicating a deep low and within the range of the ensemble means. This generally good agreement allowed for an emphasis on the more detailed ECMWF/GFS rather than too much reliance on the ensemble means for the end of the forecast period late this weekend and into Monday. ...Weather/Hazards Highlights... A busy early to mid-week will feature high winds along the Aleutians and Alaska Peninsula, potential coastal flooding along the southwest coast, and heavy precipitation from the Alaska Peninsula and along the southwest/southern coast into Southeast Alaska, as a northeastern Pacific system rotates around mean troughing/low pressure over the Bering Sea and into the Gulf of Alaska. An active, progressive pattern will promote additional rounds of precipitation and gusty winds moving west to east through late week and into the weekend. First, heavy precipitation with coastal rain and potential flooding concerns will continue into Thursday and may linger through Friday, particularly for Southeast Alaska, ahead of the initial system in the Gulf of Alaska. Meanwhile, periods of increased precipitation chances and gusty winds will continue for the Aleutians, Alaska Peninsula, and along the southern Coast as the additional Pacific systems upstream approach and track just south of the state with favored regions trending from west to east Friday-Saturday and Sunday-Monday. Mean surface troughing along the coast of Southeast as these multiple systems move into the Gulf and approach the region will keep precipitation chances in the forecast here as well, which may be heavy at times. Meanwhile, a tight pressure gradient across the North Slope between troughing to the south and a stagnant Arctic high to the north looks to cause some breezy easterly winds and blowing snow/blizzard conditions mid- to late week before winds ease into the weekend. In general, some lighter snow showers will be possible inland and along the North Slope through the period, but precipitation chances overall look to be focused further south ahead of and along the active offshore storm track. Most locations of the Interior to the North Slope will see above average temperatures as next week progresses, with the possible exceptions of the Seward Peninsula, parts of the higher mountain peaks, and southern portions of the state showing cooler than average temperatures as multiple systems move through. Forecast 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. Heading into the weekend, Arctic high pressure pushing further south will bring a cooling trend for southwest Alaska, with highs dropping into the 20s, and into the Interior and North Slope, with highs generally falling into the single digits to low teens. Putnam 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