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
   Accomplishments
   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
 
(Caution: Version displayed is not the latest version. - Issued 1850Z Aug 11, 2018)
 
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
250 PM EDT Sat Aug 11 2018

Valid 12Z Wed Aug 15 2018 - 12Z Sun Aug 19 2018

Model solutions continue to present a complex and difficult
forecast for Alaska during the extended range. At least early in
the forecast period, model consensus was sufficient on days 4-5
(Wed-Thu) to justify use of a slight majority of deterministic
guidance (ECMWF/GFS/CMC) as a basis for the forecast. At the large
scale, models/ensembles continue to show some support for breaking
down the persistent upper ridging across eastern Asia, but this
looks to be a rather slow process, with a large degree of chaos
introduced into the flow during the process. Additional
complexities are added by the potential arrival/interaction of
Arctic shortwave energy with additional energy (at least partially
of tropical origin) crossing the North Pacific. As a result of
these factors, forecast confidence rapidly decreases after day 5.
Ensemble means (ECENS/NAEFS) were used as a majority of the
forecast starting point starting on day 6, with deterministic
guidance eliminated entirely by the end of the forecast period.

Precipitation appears fairly common across much of Alaska through
the extended period with persistent upper troughing migrating from
the Bering Sea toward the Gulf of Alaska, and relatively small
scale upper-level disturbances traversing the flow. By next
weekend, precipitation may increase further in coverage across
southern mainland and southeastern Alaska, as a potential low
pressure system enters the Gulf (although confidence is extremely
low in this portion of the forecast). Farther north, confidence
has increased a bit with respect to Arctic shortwave energy
penetrating southward across the North Slope, increasing
precipitation chances across that region from Wed onward, with
sufficient cold air in place to support a mix of rain and snow.


Ryan


WPC medium range Alaskan products including 500mb, surface
fronts/pressures progs and sensible weather grids can be found at:

http://www.wpc.ncep.noaa.gov/alaska/ak_5dayfcst500_wbg.gif
http://www.wpc.ncep.noaa.gov/alaska/akmedr.shtml
http://www.wpc.ncep.noaa.gov/alaska/ak_5km_gridsbody.html