Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
547 PM EDT Thu Sep 12 2024

Valid 12Z Mon Sep 16 2024 - 12Z Fri Sep 20 2024

...Weekend Heavy Rain and Coastal Flooding/Wind Threat from
West/Southwest to Interior Alaska...
...Yet another Bering Sea Storm to impact the Aleutians and
Southwest Alaska/Alaska Peninsula early next week...


...Guidance Evaluation/Preferences...

Models and ensembles continue to highlight a protracted period of
highly energetic and progressive flow with a series of potent
storms to impact Alaska. A composite of well clustered guidance of
the 12 UTC GFS/ECMWF/UKMET offers excellent detail consistent with
above normal system predictability and WPC product continuity for
Monday/Tuesday. Prefer to switch to best compatible ECMWF and
GEFS/ECMWF ensemble means next Wednesday-Friday as the pattern and
historical pattern/guidance bias also supports rapid downstream
energy transfer on the faster side of the full envelope of
solutions.

...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 again risen to above average regarding the details
for the next storm slated during the early and 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 later period. This would confine the majority of
precipitation to the southwestern mainland and southern to
southeastern Alaska. This storm will again also produce maritime
threats of high winds and waves. Onshore, the WPC Hazards Outlook
depicts an associated risk of high winds and coastal impacts from
the Aleutians to Southwest Alaska and the Alaska peninsula 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