Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
700 PM EDT Wed Sep 11 2024

Valid 12Z Sun Sep 15 2024 - 12Z Thu Sep 19 2024

...Bering Sea storm to bring heavy rain and coastal flooding/wind
threats to West/Southwest to Interior Alaska this weekend...


...Guidance Evaluation/Preferences...

Latest models and ensembles show highly energetic and progressive
flow with a series of potent storms for Alaska and maritime
interests A composite of reasonably clustered guidance of the 12
UTC GFS/ECMWF/UKMET/Canadian offers good detail consistent with
improved to above normal system predictability and WPC product
continuity into early next week despite some lingering timing
differences averaged by the blend. Prefer the still compatible
GEFS/ECMWF ensemble means at longer time frames amid steadily
growing forecast spread and uncertainty. Manual adjustments ensure
sufficiently strong surface systems given favorable upper support
to offset weakening inherent to this blending process.

...Weather/Hazards Highlights...

A potent low pressure system tracking across the northern Bering
Sea during the weekend will slam inland to bring a threat of heavy
rains and high winds/coastal flooding to western and especially
southwest Alaska before working earnestly inland to affect the
Interior and Brooks and Alaska Ranges. These threat are depicted
on the WPC Day 3-7 Hazards Outlook. Energy will also quickly
progress underneath and eastward to spread a swath of unsettled
weather with and enhanced rains/winds/waves over the Gulf of
Alaska and inland to southern to southeastern areas of the state
in association with the storm's frontal system and triple point
low pressure system development. By Monday, uncertain lingering
low pressure over or near the northwestern mainland and shortwave
energy aloft may support persistence of lighter precipitation.

Confidence has risen to closer to average regarding the details of
the next potential storm during the early-middle part of next
week. Current guidance preference would bring the low track
through the Aleutians and southern Bering Sea, then tracking
near/offshore the Alaskan southern tier, eventually crossing
Southeast Alaska. This would confine the majority of precipitation
to the southwestern mainland and southern to southeastern Alaska.
There is also a risk a enhanced to high winds/waves given system
strength and speed.

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