Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
756 PM EDT Wed Apr 24 2024

Valid 12Z Sun Apr 28 2024 - 12Z Thu May 02 2024

...Overview...

During this period an upper/surface low will drift east from the
the Aleutians/Alaska Peninsula on Friday, across the Northeast
Pacific ocean over the weekend into early next week before pushing
into Southeast Alaska and British Columbia. North and east of this
feature, upper ridging will stretch from Southeast Alaska
northwest into the northern part of the state late week but erode
with time. Another large trough upstream with one or two rounds of
passing energy will track through the Bering Sea with a course
toward the western Alaska coast; however there is a lot of
uncertainty with the details of this feature.

...Guidance Evaluation and Preferences...

The models continue to struggle with the timing, strength and
location of the large trough and embedded energy late in the
period although consensus has it tracking through the Bering
toward the Aleutians and west coast/Southwest Mainland. This
system has QPF trending up across the Aleutians, Southwest and
western Mainland Tuesday and beyond however the specifics are
uncertain given the large spread in timing and location of the
trough; which will also impact the strength of the winds for the
Aleutians and surrounding locations. At this time, wind and
precipitation seem to be below hazardous thresholds. There was a
small improvement with model clustering with the initial
trough/low that will track trough the Gulf of Alaska and slows
near Southeast Alaska/British Columbia. Previous runs ruled the
CMC out of the running for inclusion since it was out of phase
with the ECWMF. Although the GFS has consistently been further
east/faster with this feature than the ECWMF, it did slow for the
first couple of periods and were closer within the cluster. The
preferred model blend began with ECWMF/GFS/EC ensemble means/GEFS
means at 50/30/10/10 before transitioning to 50% weighting of the
means by hour 156, 70% by hour 180 and then to 100% beyond hour
204.

...Weather/Hazards Highlights...

Gusty winds and precipitation will accompany the upper and surface
lows this weekend for portions of the Aleutians to Alaska
Peninsula, into the southwest Mainland toward Kodiak Island and
the Kenai Peninsula. At this time the wind speeds will likely
remain below the hazardous threshold but will be dependent on the
position of the upper/surface low. Some precipitation is likely
over the weekend for Southeast Alaska as moist inflow increases
ahead of the low moving east. Generally light amounts are forecast
in northern parts of the Panhandle with more moderate amounts in
southern parts. As another system approaches the Bering, Aleutians
and western Alaska, precipitation chances will renew. The timing
and location of this feature will determine where the heavier
amounts will setup for the Aleutians, southwestern and
south-central Alaska. At this time guidance is suggesting areal
average of 0.50 to 1.25 inches by Wednesday for the Aleutians.
Meanwhile the northern half of the Mainland can expect generally
dry conditions.

Above normal temperatures are expected for much of the state into
the beginning of May with the highest anomalies likely positioned
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.

Campbell


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