Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 656 PM EDT Wed Apr 23 2025 Valid 12Z Sun 27 Apr 2025 - 12Z Thu 01 May 2025 ...Overview... For much of next week, a mean upper low is forecast to spin atop the Bering Sea, pinned in place by an Arctic ridge to the north and rounds of ridging over eastern Alaska. Spokes of the trough may poke into western parts of the state at times. Meanwhile the storm track on the southern side of the upper low will lead to a few surface lows and frontal systems moving through the northern Pacific. This will spread rounds of moderate precipitation to the southern coast. At the surface expect a persistent temperature gradient between a wavy Interior front and Arctic high pressure, allowing for cooler than normal temperatures in the north and warmer than normal temperatures in the south, aside from cooler coastal areas. ...Guidance/Predictability Assessment... Recent model guidance displays a somewhat typical pattern of okay agreement on the large scale with considerably greater differences in specifics that could have sensible weather implications. There is general agreement for weak low pressure over Bristol Bay Sunday, and weak lows that may consolidate in the Gulf early Monday. Meanwhile a shortwave rounding the southern side of the Bering upper low will support surface low pressure moving eastward through the northern Pacific. The ECMWF seemed most agreeable with the ensemble means' position of the low around Monday so this seemed like a favorable cluster. The 12Z GFS had a few embedded low centers, as did the 12Z UKMET. Multiple low centers are possible but wanted to depict a consolidated low for now. The 12Z CMC started out with a position near the EC/ensemble means Monday, but by Tuesday tracked north of the eastern Aleutians/Alaska Peninsula unlike consensus. This low may interact with low pressure over Bristol Bay and vicinity by midweek and overall produce lower pressures in the southwestern Mainland. Then upstream, another low is forecast to track south of the Aleutians Wednesday-Thursday. The 12Z GFS was faster than the 06Z GFS and 12Z ECMWF/CMC consensus and was not preferred. The WPC forecast was based on a blend of mostly deterministic models favoring the ECMWF early in the forecast period. As model spread increased, used half models (mostly ECMWF) and half ensemble means in the blend for Day 6, and 60 percent means Days 7-8 to minimize individual model differences since the means were more agreeable. ...Weather/Hazards Highlights... Weak surface low pressure in Bristol Bay and the Gulf at the start of the period Sunday will allow for precipitation from the Y-K Delta into favored areas of the Alaska Peninsula into Kodiak Island and the Kenai Peninsula. By Monday weak low pressure with continued moist inflow is likely to spread precipitation from Southcentral to Southeast Alaska. Precipitation should generally be light to moderate. The next, somewhat stronger, low moving through the northern Pacific is forecast to spread rain to the Aleutians Monday and continued precipitation chances in the southern Mainland Monday-Tuesday. Later Tuesday into Wednesday, precipitation looks to become enhanced in Southcentral as the low approaches, with the heaviest amounts from the Kenai terrain into Prince William Sound, though still likely not considered hazardous amounts. Lighter precipitation is possible farther north into the Interior. Another northern Pacific low is likely to produce additional rain chances in the Aleutians midweek. Wind-wise, easterly winds could be breezy along the North Slope due to the Arctic surface ridge in place to the north. Winds elsewhere should be generally weak to moderate initially, until the Monday- Wednesday surface low coming across the northern Pacific may enhance northwesterly gap winds behind it and southerly winds ahead of it. Still, 30 to 40 knots of wind are expected rather than hazardous winds of 50 knots or greater. Cooler than normal temperatures are likely for northern Alaska into the Yukon Flats through much of next week due to persistent flow around the southeast periphery of the Arctic ridge. Meanwhile warmer than average temperatures are expected for western Alaska and across much of the Interior early next week. Anomalies will generally be warmer for morning lows relative to those for daytime highs. Southern coastal areas into Southeast Alaska should see near to above average lows and below average highs much of the period during rounds of wet weather. Tate 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