Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 659 PM EST Wed Nov 15 2023 Valid 12Z Sun Nov 19 2023 - 12Z Thu Nov 23 2023 ...High winds likely over the Aleutians on Sunday... ...High winds and heavy precipitation likely for Southeast Alaska Monday and possibly pivoting toward Southcentral Alaska by midweek... ...Overview... The pattern over Alaska will be shifting next week as an upper trough bringing below normal temperatures to the southern two-thirds of the state moves out, as ridging tracks over the Aleutians/Bering Sea eastward into the Mainland and lasting over the Interior through midweek. But lows at the surface and aloft are likely to be on the periphery of this ridge, including a deep surface low over the Kamchatka Peninsula that should erode well west of the state, but push a cold front across the Aleutians and bring some high winds there on Sunday. A low farther south should take over and track eastward likely across the northern Pacific south of the Aleutians. Additionally, guidance has now been consistent for a couple of days for upper and surface low pressure farther east in the northeast Pacific to track north into the Gulf, potentially causing enhanced precipitation and gusty winds in Southeast Alaska around Monday and then possibly into Southcentral. ...Guidance Evaluation and Preferences... Model guidance is agreeable with the overall pattern change occurring as mid-upper ridging pushes across the Aleutians and Bering Sea on Sunday and into the Mainland Monday, joining up with a western Canada ridge by Tuesday. But especially by Wednesday-Thursday, there is some model spread in timing of the ridge pushing east into Canada, with the 12Z ECMWF bringing more troughing into the state and pushing the ridge more quickly eastward than the other guidance, including (at least the 00Z) EC ensemble mean. Farther west, guidance is quite consistent in showing a strong surface low (likely <960 mb) over the Kamchatka Peninsula early next week, with good agreement on the low position and then it also weakening quickly as its energy shears eastward. Then rounds of energy coming from north and west should support an upper and surface low tracking east across the northern Pacific likely to the south of the Aleutians, but possibly pivoting north a bit by Thursday. Meanwhile farther east, low pressure and energy aloft tracking northeastward toward the Gulf of Alaska Monday-Wednesday is still expected. There has been some model waffling with how far west-east the low gets, affecting the impacts for Southeast. The 12Z guidance trended somewhat west away from the state compared to the previous 00/06Z cycle, with the exception of the 12Z UKMET that now looks like an outlier with its farther northeast (closer to the Panhandle) track. Thus the precipitation forecast trended down in most 12Z models, but models could make more adjustments going forward. Considering the model guidance handling of these features, a blend favoring mainly the deterministic 12Z GFS, ECMWF, and CMC and a bit of the ensemble means early in the period. Then increased the proportions of ensemble means in the model blend to about half by Day 7 and over half by Day 8 amid increasing spread. ...Weather/Hazards Highlights... A cold front stemming from the Kamchatka surface low approaching/crossing the Aleutians and adjoining waters should spread an area of high winds and precipitation across the region around Sunday. Additional rounds of enhanced winds are possible there by Tuesday-Thursday given the low south of the islands, first easterly winds and then northeasterly on the backside of the low. Farther east as a low tracks through the northeast Pacific, precipitation that could be heavy is likely in the Panhandle starting around Monday. While the most recent models have trended down with rain/snow amounts and there is some spread with the greatest moisture axis, will continue to monitor the details. It is becoming more likely that some enhanced precipitation comes into the southern coast of the state as the low pivots, and even more so in the next round with the low south of the Aleutians. The deep upper trough crossing the mainland early next week will bring below normal temperatures to most of the southern two-thirds of the state, with coldest departures from normal likely to be over southern areas through the Panhandle. A warming trend should progress from west to east during Monday-Thursday. The North Slope will be one area that should remain above normal through the period given relatively milder onshore flow, with anomalies increasing as part of the general warming trend over the mainland 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