Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
744 PM EDT Thu May 23 2024

Valid 12Z Mon May 27 2024 - 12Z Fri May 31 2024

...Overview...

An upper low over the northeastern Pacific early next week will
spin down as it slowly moves east. Meanwhile models suggest that
another upper low will track meander near the Bering Strait early
to midweek. As the week progresses, troughing/energy are likely to
spill east into the Bering Sea and Aleutians but with low
confidence in the details.


...Guidance Evaluation and Preferences...

Model guidance is agreeable with the large upper low and
associated surface low over the northeast Pacific gradually
drifting east while weakening early through midweek. Meanwhile,
models continue to indicate an upper low near the Bering Strait
and vicinity as the period begins, but guidance has shifted from a
southward track of the low that they showed a day ago to more of a
meandering slow westward track into midweek, so trended the
forecast that direction. While models are generally agreeable in
the low's existence, GFS runs are centered farther northeast with
it compared to the more agreeable non-NCEP models. The low's track
is also dependent on upstream features; model spread increases
upstream as larger scale upper troughing/possible closed lows and
vorticity maxima track from the Kamchatka Peninsula eastward
across the Bering Sea/Aleutians/Northern Pacific. Fortunately
there was some better agreement than a day ago as models generally
show a first upper low tracking east across the Aleutians around
Tuesday-Wednesday, though still with spread in timing, strength,
and track. especially as it moves into the northeastern Pacific
late week. Another upper low could reach the western Aleutians by
Thursday or Friday. Given all the spread in individual members,
ensemble means seem to be having problems resolving the individual
systems. Overall, rounds of troughing are likely for the western
part of the forecast domain but finer details will have to be
resolved in future forecasts.

The WPC forecast used a model blend favoring the ECMWF and CMC
early in the forecast. Gradually progressed to include more
ensemble means to half by Days 7-8 amid the increasing spread and
uncertainty.


...Weather/Hazards Highlights...

Rain amounts should be modest through the period overall. Southern
parts of the Panhandle may see a relative maximum as the northeast
Pacific upper low directs moisture there. Light to moderate lower
elevation rain and higher elevation snow is forecast in the
southeastern quadrant of the Mainland to the Alaska Range in
particular, with some light amounts farther west, and by midweek
farther north into the Interior. Energies and possible
lows/frontal systems pushing through the Aleutians to Alaska
Peninsula could lead to periodic precipitation as well. River
flooding is a possibility in a couple of spots as ice breaks
up--see the Alaska-Pacific River Forecast Center for details.

Interior Alaska is likely to see the mildest temperatures across
the state, with highs generally in the 60s to low 70s as the week
progresses with a warming trend. The Brooks Range to North Slope
should also see temperatures warm with time, from around to above
the freezing mark for highs in the Arctic Coast communities. For
the southern coast, temperatures at least for highs are forecast
to stay below normal, with 40s and 50s for the most part.


Tate


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