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