Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 456 PM EDT Sat Sep 03 2022 Valid 12Z Wed Sep 07 2022 - 12Z Sun Sep 11 2022 ...Developing Gulf low to focus a heavy precipitation threat inland into south-central to southeast Alaska mid-later next week... ...Emerging Bering Sea low threat next week could reach the mainland by next weekend... ...Guidance/Predictability Assessment... Broadly speaking, despite complexity the latest models and ensemble means offer a reasonably similar upper flow evolution for the Alaskan domain through medium range time scales. Forecast uncertainty takes a hit though as there are however differences and continuity issues with potent embedded surface systems/stream energy phasing into Wednesday, especially with low development to the south of the Aleutians as well as with the deepened extratropical low track from current west Pacific Typhoon Hinnamnor. Prefer a composite blend of the initially not that well clustered solutions of the 12 UTC GFS/ECMWF/UKMET/Canadian for days 4-6. The 12 UTC ECMWF/Canadian components of this blend act to trend WPC continuity slower with system development to the south of the Aleutians midweek, more consistent with amplified flow, but all the models tend to catch up with low consolidation/WPC continuity shortly thereafter. Accordingly, this blend then seems reasonable into Thursday/Friday. The 12 UTC UKMET/GFS seem to be more in line with and as an extension from the latest official track forecast of Hinnamnor into Wednesday/Thursday, but again and for somewhat different reasons, these models solutions return more back in line with the ECMWF/Canadian over the Bering Sea Thursday/Friday, again allowing for the composite to be used as a forecast starting point (before manual adjustments) that is also generally in line with WPC product continuity. Forecast spread increases into day 7/8 seem to support a switch to the 12 UTC GEFS/ECMWF ensemble means. ...Sensible Weather and Potential Hazards... A main emphasis of the forecast into next midweek will concern the evolution of upper trough energies and embedded lows digging from the Bering Sea to the south of the Aleutians along with how they may interact with North Pacific flow/surface system as amplifying upper troughing feed development. Expect the Aleutians into the Alaska Peninsula/western mainland will subsequently see enhancing rains and unsettled conditions by Wednesday. WPC surface progs still bring an organized low/frontal system across the region that could then strengthen over the northern Gulf of Alaska next Wednesday-Friday, then exiting into Canada. There is a growing forecast signal that this low will offer a multi-day maritime and southern to southeastern Alaskan threat of enhanced rains/winds/waves and mountain snows. To the north, the overall pattern with lowered heights and passing upper systems should also support some scattered areas of mostly light precipitation over interior portions of the mainland over the period. Upstream, energetic flow off eastern Asia into early next week to include the deepened and moist extratropical low associated with current west Pacific Typhoon Hinnamnor and lead low developments are subsequently slated to work increasingly eastward into the Bering Sea, albeit with quite a bit of system evolution uncertainties given system interaction variances in guidance. System combination and nature offers potential for deep low development contingent on energy consolidation. Accordingly, expect a maritime wind/waves threat over the Bering Sea next week along with an emerging longer time frame threat of enhanced rain/winds with possible well organized system approach toward the western mainland heading into next weekend. Schichtel 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