Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 656 PM EDT Tue May 05 2020 Valid 12Z Sat May 09 2020 - 12Z Wed May 13 2020 ...Significant Bering Sea Weekend Storm... ...Guidance/Predictability Assessment and Weather/Hazard Highlights... There is a good guidance signal in support of deep storm genesis this weekend as an anomalously deep closed low/trough aloft lifts northward over the western Bering Sea on the western periphery of a building/warming upper ridge over the mainland. Favorable upper support should help ensure a deep low/system underneath and the 12 UTC models have trended WPC continuity strongly in that direction. Surface low pressure may fall into the upper 960 mb range by 12 UTC Saturday before slowly filling over the subsequent several days. Tight pressure gradients around the low will offer a threat of high winds/seas over the Aleutians and much of the Bering Sea in addition to wrapping areas of heavy rain that could work into western and southwestern Alaska. A second developing low/frontal system may threaten the Aleutians and southern Bering Sea next Tuesday/Wednesday. This storm should also be well organized, but does not seem to have as potent support as the powerful lead system. Meanwhile, rising heights across mainland Alaska as the upper ridge builds will promote warming temperatures. High temperatures are forecast to upwards of 20 degrees above average across much of mainland Alaska through much of the forecast period, with temperatures forecast to rise into the 60s and 70s for portions up through the Interior. Underneath, low energies held down over the Gulf of Alaska and the northeast Pacific should offer limited influence on Alaska weather into next week, but flow should support periodic rainfall over the southern Alaskan tier. Overall of all the models, the 12 UTC GFS seems most in line with GEFS/ECMWF ensembles and was favored through the weekend. A composite blend of the GFS and ensembles offers a solution with system details consistent with a pattern with above normal predictability next week. Schichtel 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: - Heavy precipitation across portions of mainland Alaska, Fri, May 8. - High winds across portions of mainland Alaska, Fri, May 8. - Much above normal temperatures across portions of mainland Alaska, Fri-Tue, May 8-May 12. 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