Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 354 PM EDT Mon Jun 03 2019 Valid 12Z Fri Jun 07 2019 - 12Z Tue Jun 11 2019 The forecast once again follows the general strategy of depicting an operational model blend early in the period (day 4 Fri into day 5 Sat) and then fairly quickly adjusts toward an even model/ensemble mean weight mid-late period (through day 8 Tue) as specifics become increasingly uncertain. The 06Z GFS/FV3 GFS and 00Z ECMWF/CMC/UKMET provides operational input while the ensemble component consists of the 06Z GEFS/00Z ECMWF means. One notable adjustment/clustering in the guidance relative to yesterday is for the upper low initially north of Siberia. Models/ensembles have been wildly divergent with the ultimate track of this feature but the 00-06Z model/mean solutions are much closer together today, showing northeastward progression and a better defined leading surface front reaching the North Slope region. The general idea of high pressure progressing eastward across the Arctic during the weekend/early next week has better continuity. The 12Z GFS has reverted to a farther westward path for the upper low so confidence is still not particularly great. Farther south the specifics continue to be ambiguous but consensus/continuity show mean ridging aloft over the Bering Sea and parts of the mainland. At the surface Bering Sea high pressure and mainland low pressure/troughing prevail through the period with fairly low sensitivity to exact details aloft. Into about day 6 Sun the leading system drifting northeastward from the mid-latitude Pacific has been reasonably well forecast in principle but with typical differences in track/speed, favoring a consensus approach. Today's guidance average is a bit slower than 24 hours ago. Ahead of this system expect an upper ridge to build into the northeastern Pacific and then the Panhandle/western Canada into the mainland. This general scenario has had fairly good continuity over recent days. Farther west individual models/ensemble members diverge significantly for track and timing of individual systems. These issues begin to affect the northeastern Pacific by days 7-8 Mon-Tue, such as determining whether the initial system will persist through late period or dissipate in favor of one or more trailing waves. Although the blend includes minority weight of the 00Z ECMWF/CMC, preference reflects the ensemble means that keep best-defined (though still fairly weak) low pressure westward of the separate eastern waves depicted in those model runs by day 8 Tue. Over and south of the western-central Aleutians the primary observation is that the recent trend of ensemble members has been to trim away the northern part of the spread for low pressure/frontal systems. This would seem to provide less confidence in some recent ECMWF runs that have tended to bring low pressure and/or surface fronts at least as far north as the Aleutians by the latter part of the forecast period. Rausch 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 - 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