Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 646 PM EDT Mon May 11 2020 Valid 12Z Fri May 15 2020 - 12Z Tue May 19 2020 Pattern Overview ________________ Through the period /Fri May 15 to Tue May 19/ there has been relatively stable continuity with the synoptic pattern evolution across the Alaska domain and adjacent maritime regions. An anomalously strong Arctic high will remain in place initially with some retrogression expected to the west. This will funnel cooler mainland temperatures for much of the Interior and Arctic Coast region. A pair of strong surface lows are expected to track through the domain, the first passing through the Gulf of Alaska but well south of the Mainland. The second system is expected to pass south of the Aleutians this upcoming weekend. Guidance/Predictability Assessment __________________________________ The 12Z model guidance showed average to slightly above average synoptic scale through most of the period. Aloft, the 500 mb pattern exhibited fairly good agreement and at the surface, through about day 6, the ECMWF/GFS/CMC showed good clustering with the initial low track across the Gulf of Alaska. After that, the CMC lags the low back while the ECMWF/GFS carry it eastward early next week. The faster solutions from the ECMWF and GFS were favored. With the second area of low pressure passing south of the Aleutians late in the weekend and early next week, there is greater model spread and the CMC was largely discounted as it develops the low too deep and large compared to the more compact GFS and ECMWF. Finally, toward the end of the period and in the far western part of the domain, another area of low pressure is possible. Here, the ECMWF rapidly deepens this feature, much more than the GFS and CMC. While the ECMWF solution may be a bit of an outlier, the WPC blend favored heavily the ECENS which dampened it a bit, given the uncertainty and model spread. Weather/Hazard Highlights _________________________ There is reasonable confidence in the general trend toward cooler temperatures over a majority of the mainland over the upcoming week. Above normal readings should decrease in coverage and become more confined to southern/western areas of the state while the pattern will gradually become more favorable for below normal temperatures over northern and eastern areas. Expect significant precipitation to be fairly limited in coverage during the period owing to the southern extent of the oceanic lows and the surface high governing the overall weather pattern for central and northern sections. The front settling across the southern mainland may focus some activity at times while light precipitation may reach northeastern areas next weekend with the arrival of upper troughing. As the Gulf of Alaska system moves eastward, expect its track to remain far enough south for at most a little moisture to reach the southeast Alaska Panhandle. The system tracking over the western Pacific may bring some moisture into the Aleutians late in the weekend but with limited confidence on placement and intensity. Taylor Additional 3-7 Day Hazard information can be found on the WPC medium range hazards chart at: https://www.wpc.ncep.noaa.gov/threats/threats.php Hazards: No significant hazards are expected over Alaska during this forecast period. 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