Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
746 PM EDT Wed Jun 21 2023

Valid 12Z Sun Jun 25 2023 - 12Z Thu Jun 29 2023

...Pattern Overview and Weather/Hazards Highlights...

The dominant feature for the weekend into early next week will be
a nearly stationary closed upper low and associated surface low
over the southern Bering Sea, with multiple shortwave
perturbations pivoting around the base of it.  The first wave of
low pressure is progged to arrive early Sunday and bring moderate
to locally heavy rainfall for the coastal mountains from the
western Alaska Peninsula to the Kenai Peninsula and southern
mainland coast, with 2-4 inches of rainfall possible for the
upslope terrain.  Gale force winds are also possible across the
northern Gulf waters and this could result in potentially
hazardous maritime conditions for the upcoming weekend, followed
by improving conditions going into Monday.  Portions of the
Interior will also have isolated to scattered showers and perhaps
a few thunderstorms on most days, but overall QPF should be light
in most cases.  In terms of temperatures, high temperatures are
expected to rise into the upper 60s to middle 70s for many of the
Interior valleys, and 50s/low 60s for the central and coastal
areas.  The Arctic Coast will likely remain cooler with highs
generally in the 40s/low 50s most days.

...Guidance Evaluation/Preferences...

The 12Z model guidance suite has good overall synoptic scale
agreement for the upcoming weekend, and a multi-deterministic
model blend suffices as a good starting point in the forecast
process.  The shortwave disturbance pivoting northeast towards the
northern Gulf on Sunday continues to have a stronger signal in the
GFS, but similar in timing to the ECMWF, whereas the CMC has a
slightly slower track.  The next disturbance pivoting around the
upper gyre is generally weaker in the guidance, although the GFS
is the strongest solution with this second feature also, so
additional changes in the forecast are expected over the next few
days.  All of the guidance agrees that the main upper low will
remain nearly anchored in place across the southern Bering Sea
through about Tuesday night, before drifting eastward across the
Alaska Peninsula and towards the northern Gulf.  The ensemble
means accounted for about 50-60% of the forecast blend by
Wednesday/Thursday.

Hamrick

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