Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 622 PM EST Fri Mar 1 2024 Valid 12Z Tue Mar 5 2024 - 12Z Sat Mar 9 2024 ...General Overview... An upper level ridge that will initially be over mainland Alaska on Tuesday is expected to break down some going into Wednesday, and then replaced by a trough extending southward from the Arctic towards the end of the week, with a return to colder temperatures for western and northern portions of the state. Meanwhile, multiple low pressure systems are forecast to track south of the Aleutians and then enter the northern Gulf towards the end of the week, perhaps consolidating into one main low over the northern Gulf by Friday, and therefore result in increasing chances of precipitation for the southern coastal areas and adjacent mountain ranges. ...Guidance Evaluation and Preferences... The 12Z model guidance suite, along with the 18Z GFS, have a decent overall handling of the upper level pattern to begin the forecast period on Tuesday, although there are already some placement and intensity differences with the low pressure system tracking south of the Aleutians. The GFS is initially quite strong with this surface low and also faster with it. There is better consensus that a triple point low will develop and become the primary low as the storm system enters the northern Gulf. There will likely be a second surface low that quickly follows behind this, with closer agreement among the CMC/ECMWF compared to the GFS, which suggests a more northern track near the Aleutians. The WPC progs have this low trending farther south during the Tuesday-Thursday time period as it approaches the Gulf region compared to yesterday's forecast. In addition, there has also been a trend in the guidance for a slightly faster progression of the cold front across western Alaska late in the week, and for a colder air mass compared to the previous forecast. A multi-deterministic model blend was used as a starting point in the forecast process on Tuesday with slightly more weighting towards the CMC and ECMWF, and then up to about 50% ensemble means by next Saturday owing to the uncertain surface low evolutions over the north Pacific. ...Weather/Hazards Highlights... Enhanced precipitation is likely for the south-facing terrain of the Alaska Peninsula, Kodiak Island, and the Kenai Peninsula early in the week as the lead low pressure system advects moisture northward across these mountain ranges, mainly in the form of snow. There will likely be some abatement midweek before the next pair of Gulf lows bring additional snow to the southern mountains, and eventually the southeastern Panhandle by Friday and beyond, although many aspects of the forecast are likely to change. Over the past 24 hours, there has been a general trend for heavier snow and coastal rain during this forecast period across the southeast Panhandle region, but not to the point of reaching hazardous level criteria. Some snow showers are also likely across western portions of the mainland for the first half of the week, and then mainly dry for areas north of the Alaska Range for the middle to end of the week. In terms of temperatures, relatively mild conditions can be expected across most of the mainland through about Wednesday, although the Arctic Coast remains quite cold. A cold front crossing western mainland Alaska will likely bring readings back down to below average levels for the western half of the state, and the North Slope, by the end of the week. This will result in widespread subzero overnight lows for these areas. Hamrick 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