Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 755 PM EDT Fri Mar 25 2022 Valid 12Z Tue Mar 29 2022 - 12Z Sat Apr 02 2022 ...Overview... The primary focus of the forecast will be on a series of systems/fronts that should bring episodes of enhanced precipitation and winds from the North Pacific/Aleutians/Bering Sea into the Gulf of Alaska and nearby land areas. There is decent agreement on the general pattern but more spread on important details that will affect the location and magnitude of greatest precipitation and winds. Expected flow aloft over the mainland appears somewhat ambiguous for at least portions of the period. Best consensus of guidance highlights a mean ridge to the north/northwest of the mainland, a trough/upper low to the east, and a mean ridge over western Canada (briefly dampened by a shortwave or two). This may leave a col region over the mainland for a time but by later in the week a moderate majority of guidance suggests a tendency for the western Canada and Arctic ridges to connect to some degree. ...Guidance/Predictability Assessment... In principle there is decent clustering for the leading system heading toward the southeastern coast/Panhandle Tuesday into Wednesday. Small-scale aspects of the system still temper predictability for specifics though. Most solutions currently show a frontal wave tracking northward close to the Panhandle while the parent low south of Kodiak Island early Tuesday could track eastward behind it. Additional complexities exist with the upstream area of low pressure progressing eastward from the Bering Sea/Aleutians. At the very least the prevailing theme in latest guidance is that the core of upper dynamics should not extend as far eastward/southeastward as depicted in recent GFS runs, so the greater probability is for the parent low to track over the Bering Sea rather than over or south of the Aleutians. The GEFS mean is somewhat south of the ECMWF/CMC means but not to the degree of the GFS. Details of energy aloft will also determine how frontal waviness may evolve after midweek. ECMWF runs have been suggesting such a wave that may track into the far southwestern mainland, even with an upper evolution closer to consensus than the GFS (which ultimately keeps the wave farther south). On the other hand the 12Z CMC is much more progressive, pushing a frontal wave more toward the Panhandle. The scale of this frontal waviness is too small to be reflected in the ensemble means. Finally, there is a hint of another progressive low/front that could arrive from the west with upstream energy feeding into the eastern Bering into Pacific mean trough aloft. Models and ensembles show yet another storm tracking into the Aleutians/Bering Sea by day 8 Saturday. Some operational runs suggest it could be fairly deep. Latest ECMWF runs stray to the east or southeast side of the full guidance spread and a slower trend in the new 12Z ECMWF mean would further suggest that the operational ECMWF scenario has relatively lower probability so far. Recent GFS/ECMWF runs have differed considerably for specifics of upper flow over the mainland during the period, with the GFS tending to favor more troughing that extends from the northeast (though less pronounced in the 12Z/18Z runs) versus the ECMWF that wants to extend ridging northwest from western Canada. The full model/ensemble consensus suggests there may be a col region over the mainland into midweek, followed by the ensemble means being fairly consistent in developing more of a ridge per ECMWF runs. Guidance comparisons led to starting the first half of the forecast with a 12Z operational model blend with slightly less GFS input than average due to its lower-confidence evolution over the Bering Sea/North Pacific during that time frame. Phasing in some of the 12Z GEFS/00Z ECMWF means to complement the operational runs after early Thursday reflected the most agreeable aspects of significant features. ...Weather/Hazard Highlights... The leading system reaching the Gulf of Alaska should promote a period of moderate to heavy precipitation over the southeastern coast/Panhandle through Tuesday. The next low/frontal system over the Bering Sea and Aleutians will initially be accompanied by some organized precipitation and enhanced winds. By mid-late week a wave may develop along the front just south of or near the Alaska Peninsula--helping to focus precipitation over southward/eastward-facing locations along the Peninsula and farther east. Confidence is not yet great in the details though, as a more progressive minority scenario would push greater precip focus into the Panhandle instead. Another system merging into the larger scale circulation could maintain some degree of moist flow into parts of the southern coast through the end of the week. A potentially strong storm may bring another episode of precipitation/winds to the Bering Sea and Aleutians by next Saturday. Most of the southwestern half of the mainland will likely trend toward above normal temperatures with the highest anomalies over far southwestern locations. The remainder of the mainland should see a mix of above/below normal readings. Best potential for below normal temperatures should be over the North Slope and for morning lows. Expect the Panhandle to see below normal highs and near to above normal lows. Rausch Hazards: - Heavy precipitation across portions of the Alaska Panhandle and mainland Alaska, Mon-Tue, Mar 28-Mar 29. 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