Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 233 PM EST Thu Jan 31 2019 Valid 12Z Mon Feb 04 2019 - 12Z Fri Feb 08 2019 Overall the guidance is maintaining better than average agreement and consistency for most aspects of the extended Alaska forecast. Expect a mean ridge to extend from the eastern Pacific through Mainland Alaska through the period. This ridge should allow some upstream shortwave energy to pass through early-mid week but may become stronger and extend into the Arctic later in the week. At the same time mean troughing with one or more embedded lows should prevail over the Bering Sea and extreme northwestern Pacific. Within this mean pattern the strongest surface lows will likely track over the Bering Sea while less intense but precipitation-focusing waves track near or over the Alaska Peninsula and Gulf of Alaska. Days 4-5 Mon-Tue start with a nearly even blend of the 06Z GFS/00Z ECMWF/00Z UKMET to represent consensus details early in the period. Primary features of note in this time frame are an eastern Aleutians into eastern Bering Sea system, a leading triple point wave, and farther north a front expected to reach the northwest coast of the mainland. This front has become a little more progressive over the past day. Continuity was holding up fairly well for the southeastern Bering Sea system through the 00Z/06Z cycles but the 12Z GFS has strayed toward the southwest side of the model/ensemble envelope. Leading waviness exhibits typical run to run variability. During days 6-8 Wed-Fri the forecast blend gradually increases ensemble mean input (reaching 70 percent on day 8) while shifting emphasis at least 2/3 toward the ECMWF/ECMWF mean versus the 06Z GFS/GEFS mean. Over the past 2-3 days continuity and clustering have generally been much better than average for the strong storm tracking across the western Aleutians and into the Bering Sea albeit with some variability for progress of the associated leading front across the Bering/Aleutians. Stronger ECMWF mean depiction of this storm versus the GEFS mean favors weighting more of the former for the ensemble component of the blend. There is a fairly strong signal for another storm reaching the northwestern Pacific/western Aleutians late in the week but solutions differ in timing and track. Recent GFS runs have been in the faster portion of the spread with GEFS/ECMWF/CMC means all supporting a slower system. The downstream upper ridge has trended stronger in most guidance over the past day or so. This trend favors greater weight of the ECMWF/ECMWF mean which are stronger with the ridge than the 06Z GFS/GEFS mean. Note that the 00Z/12Z GFS runs show a stronger ridge and better represent forecast preferences. Rausch WPC medium range Alaskan products including 500mb, surface fronts/pressures progs and sensible weather grids can be found at: http://www.wpc.ncep.noaa.gov/alaska/ak_5dayfcst500_wbg.gif http://www.wpc.ncep.noaa.gov/alaska/akmedr.shtml http://www.wpc.ncep.noaa.gov/alaska/ak_5km_gridsbody.html