Alaska Extended Forecast Discussion
National Weather Service College Park MD
709 PM EDT Tue Jun 3 2025


Valid 12Z Sat 07 Jun 2025 - 12Z Wed 11 Jun 2025

...Overview...

The extended range period begins Saturday with a persistent 
upper-low over mainland Alaska that will linger through the 
weekend before drifting southward early next week. To the South, 
an upper-level low and accompanying surface frontal system will 
lift northeastward from the northeastern Pacific and into the Gulf
of Alaska. Both lingering precipitation chances from the initial 
upper-low and the approach of the next system will keep unsettled 
weather in the forecast at least through the weekend, with a 
general downward trend in precipitation expected as the Gulf 
system begins to weaken early next week. The presence of the 
persistent upper-low over the state will keep mean troughing in 
place and a period of generally below average temperatures. 


...Guidance Evaluation/Preferences...

Guidance has come into even better agreement with regards to the 
overall synoptic pattern this weekend. A persistent, lingering 
upper-low over the mainland looks to remain in place as another 
upper-low/accompanying surface frontal system over the 
northeastern Pacific lifts northward. The GFS, which was faster 
with this system the prior few days, is now in line with the ECMWF
and CMC, and all guidance shows the system trending a bit 
stronger. This will likely bring greater heavy rainfall impacts to
portions of the southern coast/Southeast. Thereafter, guidance 
begins to diverge a bit, but tends to favor two general features. 
First, the persistent upper-low over the mainland looks to 
continue, first drifting south over the southwest/southern coast 
before shifting eastward towards the Southeast. There are 
differences in the progression of this feature between the 
deterministic models, but all favor this general evolution. The 
means are less detailed, but at least the ECens and CMC ensemble 
show persistence of mean troughing shifting eastward with time. 
The surface reflection is more complex, with the latest 12Z ECMWF 
showing the potential for restrengthening and/or redevelopment of 
low pressure over the Gulf following the departure of the prior 
system. This would have the potential for increased precipitation 
chances along the southern coast. Most other guidance maintains a 
broad, strong area of high pressure over the Gulf and into the 
southern Coast. The second feature is the approach of another 
system upstream over the Bering Sea. The GFS remains faster with 
the approach of the system, but all deterministic guidance has 
come into better agreement on the general progression of an area 
of low pressure upstream of ridging in place to the east. The 
deterministic guidance is a bit faster than the means, which tend 
to hold the system back further to the west, and most guidance 
tends to agree that the ridging to the east will persist while the
system begins to weaken. Regardless, there does appear to be a 
stronger signal for at least some modest precipitation chances 
over the Aleutians with the focused moist southerly flow between 
the low pressure system and ridge. 

Given the overall good agreement on the pattern and features, the
updated WPC forecast used a composite blend of the ECMWF/CMC/GFS 
early to mid-period, with a contribution from the means later in 
the period as differences naturally increase, which captures the 
noted features without any strong preference in location/timing 
given to any one model. The most notable trends in the updated 
forecast are a stronger depiction of the Gulf system this weekend,
potential for at least lingering if not increasing precipitation 
chances for these same regions mid-next week with the persistence 
of the upper-low, and increasing precipitation chances across the 
Aleutians with the approach of the system over the Bering Sea. 


...Weather/Hazards Highlights...

Precipitation chances will continue into the weekend and into 
early next week broadly across the mainland as a lingering upper- 
low remains in place. A threat for some heavier, potentially 
impactful snow over the Brooks Range given the cold temperatures 
in place may linger into Friday and early Saturday. A more 
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. Forecast rainfall amounts have continued to trend 
upward, now in the 2-6" range, especially from Cordova southeast 
past Yakutat and into northern portions of the Southeast Saturday 
and possibly into Sunday. Some gusty winds are also expected, 
particularly for favorable gap locations. Shower chances will 
linger into early next week but with lighter amounts forecast as 
the upper-low shifts southward. An increase in precipitation 
chances may return to the southern coast/Southeast depending on 
the evolution of this system. An upper-level shortwave over the 
Arctic may also bring some increased precipitation chances to 
northwestern areas. Further west, a slow moving system shifting 
into the Bering Sea will likely bring some rainfall chances to the
Aleutians early next week with some locally heavier amounts 
possible. 

High temperatures across much of the state will remain below 
average through the weekend and into early next week as mean 
troughing remains in place in the upper levels. Most of the state 
will see highs 5-10 degrees below average, with even greater 
anomalies along the North Slope of 15-25 degrees. Forecast high 
temperatures are generally in the 30s for the North Slope, 40s and
50s for western interior/coast and Aleutians, 50s for the 
Southeast, and 50s to mid-60s for the central/eastern interior and
Southcentral. While temperatures will remain cooler and below 
average, there does look to be a slow but steady warm up through 
the period, with temperatures rising a degree or two each day, 
particularly for the interior.

Putnam



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