Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
739 PM EDT Mon Apr 7 2025

Valid 12Z Fri 11 Apr 2025 - 12Z Tue 15 Apr 2025


...Gulf low pressure could lead to heavy precipitation for the
southern coast and strong gap winds in the Alaska Peninsula this
weekend/early next week...

...Overview...

An upper low will be in place near the Bering Strait as the
extended period begins Friday. Meanwhile an upper/surface low is
forecast to track through the northern Pacific south of the
Aleutians and Alaska Peninsula. These features should interact and
combine into the weekend and early next week, albeit with model
differences in exactly how. This pattern aloft will support
surface low pressure in the Gulf, which could become reasonably
deep early next week. Mean moist southerly flow near and east of
the low could bring locally heavy precipitation to the southern
coast of the Mainland into parts of the Panhandle, particularly
over the weekend into Monday. Northerly to northwesterly gap winds
may be brisk in the vicinity of the Alaska Peninsula behind this
low over the weekend.


...Guidance/Predictability Assessment...

Model guidance is finally in somewhat better agreement regarding 
the pattern late this week. After several days of GFS runs that 
centered an upper low north of Alaska over the Arctic, recent GFS 
runs are now in better alignment with the upper low center near 
the Bering Strait Friday. Meanwhile farther south, models are also
reasonably agreeable in showing an upper low and associated 
surface low tracking west to east south of the Aleutians Friday 
and the Alaska Peninsula Saturday. Thus for the early part of the 
period, a multi-model blend of mainly deterministic models was 
able to be used.

Over the weekend into early next week, there may be some complex 
evolution of the preexisting upper low near western Alaska with 
the shortwave trough to the south, with the possible added 
complication of Arctic energy diving south through the western 
Bering Sea. Models have a common theme of an upper low persisting 
but with more spread in its position. GFS runs center the upper 
low south in the Pacific Sunday-Tuesday, allowing for a deep 
surface low in the Gulf. Meanwhile the ECMWF and CMC keep the 
upper low farther north near Bristol Bay, and the ECMWF in 
particular then produced a deep surface low there around Monday, 
unlike other guidance. Ensemble means indicate troughing across 
both areas so it was difficult to determine if one model camp was 
better than the other. With individual models diverging, the 
forecast blend ramped up the proportion of ensemble means to 
around half Day 6 and more Day 7-8 to mitigate the differences.


...Weather/Hazards Highlights...

Late this week, weak surface low pressure in the Gulf could focus
coastal rain and inland/higher elevation snow over the far south 
and Panhandle, but with mainly light to moderate amounts. Some 
areas of lighter and more scattered precipitation (mostly snow) 
will extend farther north over the Mainland. Upstream, the upper 
low could spread light snow into the southwestern Mainland late 
week. Meanwhile, North Pacific low pressure tracking eastward 
likely just south of the Aleutians Friday and Alaska Peninsula 
Saturday will allow for increasing precipitation chances and 
breezy winds there. Combining energies aloft may lead to 
strengthening low pressure in the Gulf. With this deepening low, 
northerly to northwesterly winds on the backside could be brisk to
strong across the Alaska Peninsula for the weekend and perhaps 
into next Monday. Additionally, this should provide support for 
more precipitation, with moderate to locally heavy amounts 
becoming more likely from the Kenai Peninsula into Southeast 
Alaska for the weekend into early next week. The details will 
continue to be refined in future forecasts.

The upper low forecast to be over the western Mainland Friday 
will support below normal temperatures over the western half or so
of the state. These below average temperatures should become more
limited to the western coast with time, as milder than normal 
temperatures expand westward across much of the Mainland by early 
next week. Forecast highs in the Interior should generally be in 
the 40s to low 50s by Sunday and beyond. Southeast Alaska is 
forecast to see slightly below average temperatures late this week
but warm slightly above normal, especially for lows, early next 
week.


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