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FXAK02 KWNH 282350
PMDAK

Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
750 PM EDT Tue May 28 2024

Valid 12Z Sat Jun 01 2024 - 12Z Wed Jun 05 2024

...Overview...

An initial upper low will pivot across the northeast Pacific Ocean
by the weekend while another closed upper low advances across the
Aleutians over the weekend, reaching the northeast Pacific early
next week. This pattern will a mean low across the Aleutians, the
Gulf of Alaska and southern portions of the state; which will be
supportive for precipitation to spreading along the Southern Coast
of Alaska with cooler than normal temperatures. Upper ridging to
the northeast of this storm track should promote mild to warm
temperatures over the Interior with some lighter convective
showers, at least into the weekend, but with more uncertainty
early next week as Arctic energy may approach.

...Guidance Evaluation and Preferences...

The last few runs of the deterministic models and the ensemble
means have an agreeable large scale pattern through the weekend
before the spread increases by the start of the coming week. There
continues to be no clear outlier as the models are all within the
normal degree of spread for the long range. An upper trough and an
associated surface low will be located south of Kodiak Island as
the period begins Friday and pivot toward the Gulf into Saturday,
with just some minor spread in the models. Upstream, another
upper/surface low is forecast to track east across the Aleutians
Friday-Saturday, likely crossing the eastern Aleutians into the
northern Pacific by Sunday. Additional energy rounding the base of
the upper low should help to consolidate it and possibly deepen
the surface low in the northeastern Pacific early next week.

To the north and east of the storm track, a generally ridgy
pattern aloft should be in place across much of the Mainland into
late week. Model guidance does show some possibility of Arctic
energy diving southwest toward or into the northwestern Mainland
by the weekend or early next week. This could increase the
potential for convective showers across the Mainland however this
feature remains an uncertain aspect of the forecast with low
confidence.

The WPC forecast began with a multi-model approach by including
the ECWMF/GFS/UKMET/CMC through forecast hour 144. For forecast
hour 156 and beyond the weighting of the deterministic guidance
reduced as the GEFS and EC ensemble means were included. The
proportion of ensemble means as the period progressed was
increased steadily, reaching around 50% by Days 7-8 given the
increasing uncertainty especially in northern areas.


...Weather/Hazards Highlights...

During this period no significant weather hazards are forecast.
There may be instances were the convective showers over portions
of the Interior during the afternoons and evenings produce heavy
rain which may lead to very local impacts, however the exact
location and timing is uncertain. Depending on the eventual flow
pattern over the Mainland next week, precipitation may become more
widespread and heavier, but this remains uncertain. River flooding
is a possibility in a spot or two with the seasonal ice breakup;
see the Alaska-Pacific River Forecast Center for details. For the
Southern Coast of the state--across the Alaska Peninsula (and
Kodiak Island) to the Kenai Peninsula and Prince William Sound to
the Panhandle--can expect some precipitation chances given the
favorable troughing and expected low tracks. Some localized
heavier totals in typically favored areas of terrain are possible,
but heavy amounts should not be widespread.

With weak riding in place over central/northern portions of the
Mainland daily temperatures will be near or above average.
Interior Alaska is likely to see the mildest temperatures across
the state, with highs in the 60s to low 70s late this week into
early next week, around 5-10 degrees above average. The North
Slope is likely to be closer to or below average, with highs just
above the freezing mark in the Arctic Coast communities. For the
southern coast, temperatures at least for highs are forecast to
stay below normal given the troughing and active pattern in place,
with 40s and 50s for the most part. However, 60s look to sneak
into Anchorage to Talkeetna.


Campbell/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

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