Skip Navigation Links weather.gov 
NOAA logo - Click to go to the NOAA homepage National Weather Service   NWS logo - Click to go to the NWS homepage
The Weather Prediction Center

 
 

 

Follow the Weather Prediction Center on Facebook Follow the Weather Prediction Center on Twitter
NCEP Quarterly Newsletter
WPC Home
Analyses and Forecasts
   National High & Low
   WPC Discussions
   Surface Analysis
   Days ½-2½ CONUS
   Days 3-7 CONUS
   Days 4-8 Alaska
   QPF
   PQPF
   Flood Outlook
   Winter Weather
   Storm Summaries
   Heat Index
   Tropical Products
   Daily Weather Map
   GIS Products
Current Watches/
Warnings

Satellite and Radar Imagery
  GOES-East Satellite
  GOES-West Satellite
  National Radar
Product Archive
WPC Verification
   QPF
   Medium Range
   Model Diagnostics
   Event Reviews
   Winter Weather
International Desks
Development and Training
   Development
WPC Overview
   About the WPC
   Staff
   WPC History
   Other Sites
   FAQs
Meteorological Calculators
Contact Us
   About Our Site
 
USA.gov is the U.S. Government's official web portal to all federal, state, and local government web resources and services.
 
Alaska Extended Forecast Discussion
 
(Latest Discussion - Issued 2357Z Oct 23, 2021)
 
Version Selection
Versions back from latest:  0   1   2   3   4   5   6   7   8   9   10   
 
Abbreviations and acronyms used in this product
 
View Alaska Map

Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
757 PM EDT Sat Oct 23 2021

Valid 12Z Wed Oct 27 2021 - 12Z Sun Oct 31 2021

...Overview and Guidance/Predictability Assessment...

The medium range forecast over Alaska shows a persistent pattern
with an upper low northwest of the state, with rounds of troughing
tracking around it. One such shortwave trough is forecast to push
across the Alaska Peninsula Wed-Thu, before deeper troughing
establishes itself south of the Aleutians in the northeast Pacific
on Friday and tracks slowly eastward over the weekend. Model
agreement starts to go awry particularly with this second trough
and its associated surface low. The 12Z UKMET quickly becomes a
strong/fast/northern outlier near the Aleutians Thu-Fri, while the
12Z CMC is somewhat slower/south. The 12Z GFS and ECMWF align
fairly well to begin with, but by Friday into the weekend the GFS
shows a northern track of the surface low closer to the Alaskan
coast (and thus copious amounts of precip) compared to the farther
south ECMWF. The ensemble mean solutions have somewhat of a middle
ground placement of the low, so using these seemed most prudent
for now.

Farther upstream, a possibly closed low is forecast to move east
across eastern Russia from midweek onward, while a southern stream
low of possibly tropical origin tracks northeast but well to the
south of the Aleutians. These features may end up combining as
particularly the CMC shows, or stay separate, but confidence is
low with this evolution.

Therefore, WPC's forecast for Alaska began with a deterministic
model blend heavily favoring the GFS and ECMWF early in the
period, but gradually transitioned to using a blend of mainly the
GEFS and EC ensemble mean solutions by Friday into next weekend.

...Weather/Hazard Highlights...

As a relatively weak low pressure system tracks across the Bering
Sea Wed and toward Southcentral Alaska Thu-Fri, precipitation and
possibly gusty winds should increase somewhat from the eastern
Aleutians to Southcentral, while generally rainy conditions
continue for the Panhandle with convergent flow. Then by Friday
into the weekend, the amount of precipitation expected will be
dependent on the surface low track in the Northeast Pacific/Gulf
of Alaska. Heavy amounts are possible if the low takes a northern
track more like the 12Z GFS, but lighter to moderate amounts are
forecast with a southern low track. Meanwhile, generally quiet
conditions are expected for much of mainland Alaska, with
occasional snow showers along the southwestern mainland and the
North Slope and Arctic Coastal Plain.

Expect above normal temperatures to dominate much of interior
Alaska to start the medium range period next Wednesday. A slow
cooling trend is anticipated for the entire area as heights aloft
are forecast to slowly decrease due to the slow approach of the
broad cyclonic circulation over the Gulf. The southwestern
mainland may see temperatures well below average with this
cooldown, with highs 10-20F below normal, and temperatures should
become below normal farther east into the Panhandle as well.

Tate


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