Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
739 PM EDT Thu Jun 27 2024

Valid 12Z Mon Jul 01 2024 - 12Z Fri Jul 05 2024

...Overview and Guidance Evaluation/Preferences...

The ensemble means from the GEFS, EC, and CMC remain in good to
excellent agreement on the evolution of the upper-air pattern
across Alaska through the medium-range period.  The Rex Block
upper-air pattern setting up in the vicinity of Alaska during the
short-range period will persist into much of the medium-range
period.  Models continue to depict an initially deep Bering Sea
low will weaken as it slides to the south of an upper ridge that
will be anchored across northern Alaska.  Since yesterday, models
have further slowed down the eastward motion of the low into the
Gulf of Alaska by the middle of next week.  The deterministic
solutions are even slower in this regard, with the CMC begins to
hint at a retrograting pattern setting up by late next week.

The WPC medium-range grids for Alaska was based on a general model
compromise of 40% from the 12Z GFS and GEFS, 40% from the 00Z EC
means and 12Z ECMWF, and 20% from the 12Z CMC and CMC mean.  This
blend yielded a solution very compatible with yesterday's forecast
package.


...Weather/Hazards Highlights...

The medium-range period will begin with a rainy pattern across the
Aleutians and Alaska Peninsula as the lingering Bering Sea cyclone
gradually slides across these areas before drifting farther to the
east or southeast by early next week.  This gradually weakening
cyclone will allow for modest rainfall in its vicinity, but some
moderate rain can be expected from the southeast coast of the
Alaska Peninisula into Kodiak Island and the Kenai Peninsula on
Sunday.  The terrain in south-central and northern Alaska are
expected to have the best chance of showers and thunderstorms. 
There is also the possibility of dry lightning strikes during the
afternoons and evenings which would increase the risk for fire
weather concerns given the dry fuels across the region.

Ridging across mainland Alaska will maintain warm to hot
temperatures.  Afternoon maximums should lie the 80-90F range for
the most part across the eastern interior sections.  Highs mostly
in the 60s and 70s are expected across lower elevations of
south-central Alaska, with mainly 50s and 60s in most coastal
areas, 50s and 40s across the North Slope, and mid to upper 40s in
the Aleutians.  Higher elevations in the terrain across
south-central and southeast Alaska should fall below freezing
overnight.  The North Slope will cool down closer to normal
temperatures by Sunday as a surface high pressure system gradually
sliding from west to east off the northern coastline of Alaska
funnels colder air into the area from the Arctic Ocean.  Similar
temperatures are expected to last into late next week across
mainland Alaska but with a gradual expansion of the coverage of
scattered showers and emedded thunderstorms when upper shortwave
energy from the Arctic Ocean could pentrate the upper ridge and
destabilize the atmopshere.

Kong/Roth


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