Alaska Extended Forecast Discussion
National Weather Service College Park MD
620 PM EDT Wed Jun 4 2025
Valid 12Z Sun 08 Jun 2025 - 12Z Thu 12 Jun 2025
...Another Gulf of Alaska storm to bring a heavy rainfall threat
and winds to Southcentral and Southeast Alaska this weekend...
...Guidance Evaluation/Preferences...
The WPC Alaskan medium range guidance suite was mainly derived
from a composite blend of well clustered guidance of the 12 UTC
GFS/ECMWF/UKMET/Canadian models valid for Sunday and Monday. This
solution has good ensemble and machine learning guidance support
and maintains good product continuity in an active pattern with
above average predictability. Guidance offers reasonably similar
larger scale flow evolutions into next week, but model forecast
spread and uncertainty grows more rapidly with smaller scale
system depictions. Accordingly, prefer to pivot to a composite of
better clustered guidance of the 12 UTC GEFS/ECMWF/Canadian
ensemble means for these longer time frames in overall more
benign flow over the state. In this blend, applied greater
weighting to the ECMWF ensemble mean that generally seems best in
line with more common multi-model details.
...Weather/Hazards Highlights...
A concentrated area of heavier rainfall is expected along the
southern coast and into the Southeast this weekend as another
upper-low/accompanying surface frontal system lifts from the
northeastern Pacific into the Gulf bringing a fetch of Pacific
moisture. This collaborated threat is depicted on the WPC Hazards
Outlook. Some quite gusty winds are also expected, particularly
for favorable gap locations around the main low.
Meanwhile, expect scattered precipitation chances will continue
Sunday into Monday down mainly across the west-central mainland
as focused locally by a slowly southward shifting upper low. This
low will gradually work from the northern to eastern Gulf of
Alaska next week to support a moderately unsettled and rainy
pattern from coastal Southcentral to the Southeast in replacement
of the much wetter/windy lead southern stream Gulf of Alaska low.
Upstream, high latitude system translations have less than stellar
run to run guidance continuity, but offer a pattern for some
increased precipitation chances to northwestern areas of the
state next week as moisture is channeled around a building ridge
into Southwest/West Alaska in the wake of the exiting weekend
Interior upper low. Also, a series of uncertain Pacific systems
slated to work into the Bering Sea and Aleutians will likely
bring some enhanced rainfall chances in unsettled flow, with depth
and detail emerging into shorter time frames to monitor.
Schichtel
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