Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 624 PM EDT Fri Sep 02 2022 Valid 12Z Tue Sep 06 2022 - 12Z Sat Sep 10 2022 ...Heavy precipitation threat for south-central Alaska by next midweek... ...Guidance/Predictability Assessment... The WPC Alaskan Day 4-8 product suite was primarily derived from a composite blend of reaonably well clustered guidance of the 12 UTC GFS/ECMWF/Canadian for days 4/5 (Tuesday/Wednesday) before switching to a blend of the still compatable 12 UTC GEFS/ECMWF ensemble means for days 6-8 amid growing forecast spread. This forecast strategy was collaborated with local Alaskan NWS offices. WPC product continuity was reasonably well maintained in this manner in a pattern with near normal overall predictability lowering a bit into longer time frames. Forecaster applied adjustments to these resultant blends tend to mitigate unwanted embedded system weakening due to the blend process when upper support or continuity seemed to mandate as consistent with predictability. ...Sensible Weather and Potential Hazards... The lead emphasis of the forecast starting early next week will concern the evolution of upper trough energies and embedded lows moving across the Bering Sea along with how it 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 rain and unsettled conditions develop into Tuesday-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 interations 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 Hazards: - Heavy rain across portions of mainland Alaska, Wed-Thu, Sep 7-Sep 8. 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