Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
613 PM EST Sat Jan 18 2020
Valid 12Z Wed Jan 22 2020 - 12Z Sun Jan 26 2020
A mean trough/upper low is forecast to develop/persist across the
Arctic Ocean north of Alaska and Siberia through the the middle of
next week, with an active storm track across the North Pacific,
generally south of the Aleutians, and into the Gulf of Alaska.
Models/ensemble today have solidified a trend toward developing a
negatively tilted upper ridge axis from the Gulf of Alaska across
the Alaska Peninsula and into the eastern Bering Sea by late next
week. If this occurs, it would allow for the potential for
shortwave energy originating in the arctic to amplify and dive
southeastward around the eastern side of the ridge, potentially
affecting eastern portions of Alaska with colder temperatures. The
ridge also appears to be wreaking some degree of havoc with
respect to the evolution of low pressure systems in the
aforementioned North Pacific storm track, with spread quickly
increasing by the latter part of the forecast period. A blend of
the ECMWF/GFS served as a forecast starting point early in the
period, with a low pressure system forecast to track into the
southern Gulf of Alaska, spreading widespread precipitation into
the Alaska Panhandle. Following low pressure systems in the series
show greater spread, with some consensus that another system
should track south of the Aleutians Thu-Fri and into the Gulf on
Sat, and perhaps another passing south of the Aleutians Sat night
into Sun (although confidence is quite low by that point in time).
Given the increased spread, began quickly boosting components of
ECENS/GEFS ensemble means in the forecast starting on day 5 (Thu)
through the remainder of the forecast period.
Ryan
Additional 3-7 Day Hazard information can be found on the WPC
medium range hazards 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