Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 543 PM EST Sat Mar 02 2024 Valid 12Z Wed Mar 06 2024 - 12Z Sun Mar 10 2024 ...General Overview... An upper level ridge over Alaska during the short range is expected to begin to break down by the medium range period, as a trough extends southward from the Arctic, also bringing with it a return to colder temperatures for much of the Mainland. Meanwhile, a low pressure system are looks to track south of the Aleutians and into the northern Gulf towards the end of the week, with an in increasing chance of precipitation for the Southern Coast and Southeast Alaska and adjacent mountain ranges. A deep surface low over the western Aleutians around Friday, may send some additional energy into the Gulf by next weekend. ...Guidance Evaluation and Preferences... There was enough agreement amongst the 12z model guidance to use a purely deterministic model blend for the first couple of days of the forecast period, although still some considerable uncertainty in the details of individual systems. There are some placement differences in placement of a surface low south of the Aleutians on Wednesday, but eventually models converge on decent positioning for this system as it strengthens and moves into the Gulf by Friday. At the same time, another deep surface low will be approaching the western Aleutians. With the new 12z runs, there is better agreement that triple point energy should slide southeastward across the central Aleutians, reinforcing deep low pressure/troughing in the Gulf next weekend. The 12z GFS is quicker with this transition and actually brings the entire system into the Gulf vs the ECMWF and CMC which suggests some energy/a weak surface low gets left behind near the Western Aleutians, likely due to stronger ridging developing upstream. Interestingly, the ECMWF-based machine learning models seem to support more the GFS solution, suggesting this solution should not be discounted. A second low may approach the western Aleutians next weekend, but with more uncertainty on its placement. The WPC progs incorporated the ensemble means into the blend the second half of the period, with a 50/50 blend of the deterministic models and ensembles. Overall, this maintained good continuity with the previous WPC Alaska forecast. ...Weather/Hazards Highlights... Precipitation chances increase across Southeast Alaska through the period as a couple of surface lows and frontal systems affect the region. Multi-day totals of several inches of precipitation is possible, especially next weekend. Precipitation (rain and mountain snow) should extend back into the Southeast Coast/AK Peninsula and portions of the mainland under general unsettled flow/troughing, but with much less intensity. The Aleutians should stay wet and unsettled much of the period as several systems move through. In terms of temperatures, relatively mild conditions can be expected across most of the mainland through about Wednesday, with well above normal temperatures across Western and interior Alaska. 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 and lasting into the weekend. Santorelli 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