Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
615 PM EDT Sat Apr 20 2024

Valid 12Z Wed Apr 24 2024 - 12Z Sun Apr 28 2024

...Overview with Guidance Evaluation and Preferences...

12 UTC GFS/ECMWF/UKMET/Canadian model solutions are reasonably
clustered with ensembles in a pattern with above normal
predictability overall for mid-later next week. This primarily
entails the slow weakening and meandering of a main deep low over
the Bering Sea and the building of a warming upper ridge over the
mainland, albeit with uncertain weaknesses aloft down toward
Southeast Alaska. Prefer a composite blend coupled with manual
adjustments to restore Bering Sea low pressure lost in the
blending process due to displacement variances.

Opted to increase blend weighting for the GEFS/Canadian/ECMWF
ensemble means to maintain maximum product continuity heading into
next weekend amid growing system and stream phasing differences in
guidance, mainly with respect to a growing signal to lift ample
Pacific low energy and moisture up into the western then northern
Gulf of Alaska. However, the ECMWF is the least supportive of this
system, highlighting lingering uncertainty.

...Weather/Hazards Highlights...

A main storm under the influence of an amplified/closed upper
trough/low aloft will linger and meander next week over the Bering
Sea to enhance winds and waves, with flow periodically wrapping
into coastal communities. Guidance is keeping precipitation
amounts relatively modest thus far. Surface low/front details over
the Aleutians/Bering Sea become more uncertain later in the week,
but there is a good signal for the general persistence of cyclonic
flow with slowly rising pressures. This could still provide
continued inflow into western Alaska. There is also a growing yet
still uncertain signal that additional digging and subsequent
rounding of ample upstream energies under the base of the main
upper trough could act to interact with Pacific system energies
set to track underneath to the south. This could result in the
lifting of Pacific low energy and rain fueling moisture up into
the western to northern Gulf of Alaska by next weekend to monitor.
Elsewhere, in advance of this, a weaker lead system tracking
across the northeastern Pacific may bring a period of mostly light
precipitation to the Panhandle into later next week with a lower
confidence due to the forecast spread.

Most of the state should see above normal temperatures during next
week, with the highest anomalies tending to be over the Interior.
To the north of a front settling over the central mainland, cold
high pressure over the Arctic may keep temperatures near to
somewhat below normal across the North Slope. Locations near the
Southcentral coast and northern Panhandle may also see near or
slightly below normal readings.

Schichtel


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