Alaska Extended Forecast Discussion
National Weather Service College Park MD
659 PM EDT Mon Jun 30 2025


Valid 12Z Fri 04 Jul 2025 - 12Z Tue 08 Jul 2025

...General Overview...

The upper pattern will be characterized by a stable upper level 
high over the North Slope/Brooks Range later this week and 
into/through the weekend. To the south, at least a couple systems 
will traverse the Aleutians/Alaska Peninsula and into the Gulf, 
bringing enhanced rainfall chances to these regions as well as the
southern coast. This pattern will be conducive to warm to hot 
temperatures and enhanced thunderstorm chances over the interior 
which may spark some fire concerns. 

...Guidance Evaluation/Preferences...

The 12Z model guidance suite was in relatively good agreement 
overall with the handling of the main upper features in a blocky 
pattern with an upper high over the northern interior/North Slope 
and a persistent upper low in the Aleutians to Alaska Peninsula 
vicinity. The largest differences were associated with the 
evolution of the upper low/individual waves/surface systems across
the Bearing, Aleutians, and into the Gulf. The GFS/ECMWF/CMC were
all well clustered through day 5 (Friday/Saturday) depicting an 
initial surface low pressure/frontal system over the Gulf 
weakening with eastward progression as ridging increased to the 
east, and a second surface low pressure/frontal system associated 
with an upper-low to the west crossing the Aleutians to Alaska 
Peninsula. Then, the GFS diverges from the ECMWF/CMC, and shows a 
second upper low developing upstream over the Bering Sea, with the
two remaining separate features through the next couple of days 
as they both progress eastward. The ECMWF/CMC, as well as the 
ensemble means, show the initial upper low persisting as the main 
feature and remaining slow in eastward progression. The means 
tended to progress a bit faster, with the ECMWF and even moreso 
the CMC slower through late this weekend and into early next week.
Additional shortwave energy looks to reinforce the low 
pressure/frontal system by early next week with some uncertainty 
in the exact evolution of the pattern. Regardless, the pattern 
supports rain chances for the Alaska Peninsula and southern Coast 
through at least this weekend, with more scattered chances into 
the interior, and additional rain chances westward through the 
Aleutians but with more uncertainty with the specifics given 
increasing smaller-scale differences. The updated WPC forecast 
used a composite blend of the GFS/ECMWF/CMC through day 5, with 
the ECens/GEFS means replacing the GFS for days 6-8 as the GFS 
diverges from the other solutions and uncertainty grows.


...Weather/Hazards Highlights...

A blocky pattern with an upper high anchored over the 
central/northern interior and North Slope will promote warm to hot
temperatures through this weekend and into early next week. Highs
south of the Brooks range may reach the mid- to upper 80s, with 
70s for the North Slope outside of coastal regions. Thunderstorm 
chances may increase by later in the week as anomalous easterly 
flow around the upper high increases instability when combined 
with very warm surface temperatures. Thunderstorms without much 
rainfall could lead to fires started by lightning, especially 
across the Tanana Valley as well as the Copper River Basin and 
Lower Kuskokwim delta region.

To the south, the passage of at least a couple systems into the 
Gulf will bring wet weather to the Alaska Peninsula and southern 
coast. The rainfall looks to be heaviest for the Alaska Peninsula 
through the 4th, and then eastward along the southern coast 
including Kodiak Island and the Kenai Peninsula through at least 
the 5th. Rainfall chances, including heavier rainfall, may linger 
especially for the southern coast into early next week. An 
additional system upstream may also bring some rainfall, 
potentially heavy, to the Aleutians. In contrast to the north, 
highs here will remain cooler and below average with persistent 
cloud cover and showers, mostly in the 50s and 60s. The Southeast 
may see some precipitation chances depending on system evolution, 
but the region should be mostly drier than average throughout the 
period, with highs in the 50s and 60s here as well. 


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