Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 753 PM EDT Sun Mar 27 2022 Valid 12Z Thu Mar 31 2022 - 12Z Mon Apr 04 2022 ...Overview... Today's models and ensembles still show an active pattern over the North Pacific and vicinity, bringing periods of enhanced precipitation and/or brisk to strong winds across the Aleutians and southern coast of the mainland. Highest precipitation totals should be along the Alaska Peninsula into the Kenai Peninsula with some moisture extending to the Panhandle as well. Guidance shows elongated ridging aloft over the mainland late this week but energy within cyclonic flow to the east/northeast may lower heights thereafter as a high closes off over the Arctic. At the surface, the mainland will likely be in a persistent gradient between Arctic high pressure and North Pacific/Bering Sea lows. ...Guidance/Predictability Assessment... A 12Z GFS/ECMWF/CMC blend early followed by inclusion of the 12Z GEFS/00Z ECMWF means along with those models later in the period provided the best account for the most common themes of guidance/latest refinements and then resolving differing ideas for specifics within a fairly agreeable large scale pattern. Over the past day guidance has trended stronger with a developing frontal wave that should track to around the Alaska Peninsula by early Friday. Latest ECMWF/CMC runs have gravitated somewhat toward GFS runs that have tended to keep the system near the Peninsula versus continuing into the Bering Sea or southwestern mainland. As has been the case in recent days, there is still a minority scenario that is farther east--now represented by the 12Z UKMET and CMC mean instead of the CMC that had previously served that role. The stronger depiction of this wave has led to a moderate westward adjustment for heaviest associated precipitation. Continuity is good for rapidly arriving upstream energy to interact with the upper dynamics to yield low pressure near or south of the Alaska Peninsula by early Saturday, though it remains to be seen whether by persistence of the original low or redevelopment. There are still notable differences for developing western Pacific low pressure that should track across the Aleutians/southern Bering Sea during the weekend, with emphasis transitioning to or near the Gulf of Alaska by next Monday. Operational model differences include the latest GFS/CMC runs tracking the parent low into the Bering Sea with a leading frontal wave ultimately reaching the vicinity of the Gulf in contrast to the ECMWF that is faster and farther south with the main low, with the system itself tracking into the Gulf. UKMET runs have been on the fast side of the spread thus far. The ensemble means have been favoring a primary system track into the Bering Sea though perhaps not holding it as far west as some CMC runs, while hinting at potential for leading triple point development. The preferred model/mean blend offers reasonable continuity and a good intermediate evolution relative to the array of guidance. Over the past day or so the guidance has shown a tendency for mainland ridging aloft as of Thursday to be replaced by a weakness as a high closes off over the Arctic and energy arrives from cyclonic flow to the east/northeast of the mainland. Confidence in specifics is not great given the complexity of the flow. ...Weather/Hazard Highlights... A fairly vigorous developing North Pacific frontal wave tracking toward the Alaska Peninsula Thursday should bring an episode of locally heavy precipitation and brisk to strong winds to the Peninsula and vicinity. Highest totals should be along the eastern half of the Peninsula and perhaps as far east as the Kenai Peninsula. Specifics will depend on small-scale system details that tend to have low predictability a few days out in time. Moisture along this system's leading front as well as a trailing front will likely bring a couple periods of precipitation into the southeastern coast and Panhandle. A strong upstream Pacific system should track into the Bering Sea or Aleutians, with either the system itself or a leading wave reaching into or near the Gulf of Alaska by early next week. Details of this evolution remain unresolved but most possible scenarios would bring a period of precipitation and brisk to strong winds to the Aleutians, followed by precipitation of varying intensity reaching the Alaska Peninsula and southern coast/Panhandle. Continue to expect mostly above normal temperatures over the southwestern half of the mainland, with greatest anomalies for highs over far western areas and those for lows somewhat more widespread over the south and west. The rest of the mainland should see a mix of above/below normal readings, with below normal temperatures most likely over the North Slope/northeast-interior part of the mainland. The transition of the upper pattern from moderate ridging on Thursday to some degree of troughing or shear axis may lead to a gradual cooling trend over some areas during the period. The Panhandle will likely see below normal highs and near to above normal lows. Rausch 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