Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
536 PM EDT Sun Apr 21 2024

Valid 12Z Thu Apr 25 2024 - 12Z Mon Apr 29 2024

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

12 UTC GFS/ECMWF/UKMET/Canadian model solutions are well clustered
with ensemble means into later this week. This mainly entails
meandering a primary low over the Bering Sea and the building of a
warming upper ridge over the Interior. A composite solution
maintains good detail in this time frame.

Guidance solutions remain reasonably well clustered into next
weekend, but pattern evolution continuity compared to
yesterdayâ€s runs is less than stellar, lowering forecast
confidence. The newer runs offer a more rapid transition of Bering
Sea upper trough/low energy into the Gulf of Alaska at the expense
and uncertainty of the entrainment of Pacific system energies.
Prefer to quickly pivot to an ensemble mean blended forecast
approach by Saturday in an attempt to mitigate lowering
predictability, with a solution that is somewhat less progressive
than the models over the Gulf of Alaska. This seems more
reasonable considering overall amplitude. Applied manual
adjustments to restore maritime low pressure depth lost in the
blending process due to displacement variances considering
potential support aloft.

...Weather/Hazards Highlights...

A main storm under the influence of an amplified/closed upper
trough/low aloft will linger and meander into later this week over
the southern Bering Sea to enhance winds and waves, with enhanced
flow periodically wrapping into coastal communities from the
Aleutians to Southwest Alaska. Surface low/front details over the
Aleutians/Bering Sea become more uncertain late week, but there is
a good signal for the general persistence of cyclonic flow with
slowly rising pressures into Thursday/Friday. There was an
uncertain signal yesterday 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. However, latest model and
ensemble trends instead now steadily progress the main Bering
system and wholesale significant height falls bodily and with
transition into/across the Gulf of Alaska Friday through the
following Monday. This would offer a protracted maritime hazard.
This would also focus flow/rainfall from the Alaska Peninsula and
Kodiak Island out across South-Central to Southeast Alaska later
in this forecast period from mainly the Bering Sea origin system
and to a lesser certainty any Pacific based entrainments to still
monitor for added moisture availability.

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 north-central mainland,
cold high pressure over the Arctic may keep temperatures near to
somewhat below normal, especially 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