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FXAK02 KWNH 312331

Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
730 PM EDT Wed May 31 2023

Valid 12Z Sun Jun 04 2023 - 12Z Thu Jun 08 2023

...A stalled deep layer low will bring multiple days of heavy
precipitation and perhaps strong winds to the Alaska
Peninsula/Southcentral next week...

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

Early next week, an upper and surface low feature looks to move
east across Southeast Alaska, with reasonably good model
agreement. Farther north, another upper low centered just north of
Alaska should continue to shift northeast away from the state
early next week, with some minor variations in the position but
within typical model spread for this lead time. But the main
weather feature affecting Alaska through the period is ample
energy over the Bering Sea and vicinity into much of next week.
There is likely to be an initial stacked low near the eastern
Aleutians Day 4/Sunday before additional energy and low pressure
comes into the same region. There are some model differences in
the evolution of the combination of these energies, with perhaps a
slower trend to combine the two compared to yesterday's forecast
and model guidance. Though within this slower trend, the 12Z UKMET
did appear to be an outlier as it was even slower than other
guidance. Preferred instead the more agreeable 12Z GFS/ECMWF/CMC
and the ensemble means for the forecast. This worked well through
much of the period and provided an average solution for some
waffling model guidance with the positions of the upper and
surface lows stalling with time. Gradually increased the
proportion of ensemble means with lead time, but was able to
maintain a majority deterministic blend through the period with
the fairly good synoptic scale agreement. One area of uncertainty
that will have to be monitored is the interface of this upper low
and ridging farther east over western Canada, and which influence
will win out to affect the pattern over Southeast Alaska.

...Sensible Weather and Potential Hazards...

A round of light to moderate rain is likely to affect Southeast
Alaska early next week coincident with the upper and surface lows
moving through. Light to moderate rain (snow in higher elevations
of the Brooks Range) could also be in store for parts of the
western/central Mainland this weekend, followed by a drier trend
for both regions around Tuesday before potentially renewed
precipitation chances for midweek. Meanwhile the strengthening
deep layer cyclone over the Aleutians into next week should bring
increasing moisture flow onshore to the Aleutians first for some
moderate rain amounts there, followed by increasing precipitation
chances and amounts for the Alaska Peninsula eastward into
Southcentral and the Kenai Peninsula. These areas are most likely
to see heavy amounts of mainly rain, though with some snow
possible in the highest elevations. Precipitation looks to begin
Sunday with the heaviest amounts on Monday-Tuesday while some
precipitation lasts into the middle of next week, and multi-day
rain totals could be several inches for parts of Southcentral
Alaska. High available moisture values will be likely as an
atmospheric river transports moisture from what is currently
Typhoon Mawar. Strong winds could also be a threat ahead of the
lows especially over marine and adjacent areas.

A warming trend is in store for areas north of the Alaska Range
next week after a cool period in the short range, as the upper
troughing over the northern Mainland lifts out and warm front
moves north. Temperatures should generally warm to near average
Sunday and above average on Monday and beyond in the lower
elevations, though the higher elevations of the Brooks Range may
take longer to moderate. Afternoon highs will likely rise into the
70s for lower elevations of the Interior for Monday-Thursday, with
lows perhaps staying in the low 50s by midweek. However, the upper
low and the coincident rain and cloudiness chances could keep high
temperatures down below normal along the southern coastal regions.
Southeast Alaska may warm somewhat as the period progresses,
though this will depend on whether the influence of the upper
ridge reaches that far west or if it remains farther east over


- Heavy precipitation across portions of mainland Alaska, Mon-Tue,
Jun 5-Jun 6.

Additional 3-7 Day Hazard Information can be found on the WPC
medium range hazards outlook chart at:

WPC medium range Alaskan products including 500mb, surface
fronts/pressures progs and sensible weather grids can also be
found at: