Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
659 PM EDT Tue Apr 22 2025

Valid 12Z Sat 26 Apr 2025 - 12Z Wed 30 Apr 2025

...Overview...

This weekend into early next week, mean troughing is forecast 
atop much of the Bering Sea, with mean ridging just to the east 
over portions of Mainland Alasak. Spokes of the trough may poke 
into the state at times and support some precipitation especially 
along the western and southern coasts. At the surface expect a 
persistent 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. Surface lows and frontal systems are likely
to move through the northern Pacific, and one such system looks 
to particularly consolidate and track south of the Aleutians and 
Alaska Peninsula Monday-Wednesday, spreading some possibly heavier
precipitation to the southern coast.


...Guidance/Predictability Assessment...

Even early in the medium range period over the weekend, model 
guidance continues to show differences in terms of upper low 
positioning, the trough axis, and locations of shortwaves and 
surface lows. For example, by 12Z Sunday the best model consensus 
seems to be the 12Z ECMWF/CMC and 06Z GFS in showing a closed low 
north of the eastern Aleutians. However the 12Z GFS takes this 
energy farther south into the northern Pacific, while the UKMET 
shifts it quickly east. These model differences persist early in 
the workweek. Meanwhile some weak energy may be atop Southeast 
Alaska over the weekend before building ridging early next week.

Then a secondary upper low looks to round the southern side of 
the broader trough, tracking over the northern Pacific south of 
the Aleutians Sunday-Tuesday and the Alaska Peninsula Tuesday-
Wednesday along with a surface low. There is good model consensus 
for this system to exist, but continued spread in the placement. 
The 12Z ECMWF seemed particularly slow compared to dynamical and 
AI/ML model consensus with this feature and was not favored. Other
deterministic models also showed some spread but in general the 
12Z Tuesday position of deterministic models was a bit farther 
east than the ensemble means that were well clustered with the low
position.

The WPC forecast was based on a blend of mostly deterministic 
models with some EC ensemble mean component early in the forecast 
period. As spread increased, flipped to more than half ensemble 
means by Days 6-8 as the means were more agreeable. 


...Weather/Hazards Highlights...

Light to modest precipitation is forecast across the Alaska 
Peninsula to Kodiak Island and the Kenai Peninsula this weekend. 
Farther north, light rain and snow are possible in the western 
Mainland under a spoke of the upper trough. Moist inflow also 
should continue in southeast Alaska for light to moderate rain. 
Then into early next week, more focused/heavier precipitation 
could occur from the Alaska Peninsula into Monday and spreading 
into Southcentral and Southeast by Tuesday and Wednesday with the 
consolidating northern Pacific low pressure. Some lighter 
precipitation may spread into the Interior. 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, until the possibly stronger low coming
across the northern Pacific late week may enhance northwesterly 
gap winds behind it and southerly winds ahead of it.

Cooler than normal temperatures are likely for northern Alaska 
into the Yukon Flats through the weekend and early next week due 
to persistent flow around the southeast periphery of the Arctic 
surface ridge. Meanwhile warmer than average temperatures are 
expected from the Seward Peninsula south and east through most of 
the rest of the Mainland, though cooler for the southern coast. 
Anomalies will generally be warmer for morning lows relative to 
those for daytime highs. Near average lows and below average highs
are likely in Southeast Alaska 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