Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
238 PM EDT Mon May 20 2019
Valid 12Z Fri May 24 2019 - 12Z Tue May 28 2019
Models showed relatively agreement during the first part of the
extended period (Fri-Sat). The consensus is that a low pressure
system should approach the Alaska Peninsula during that time
frame, moving into the eastern Bering Sea. Given somewhat improved
consensus, the forecast during days 4-5 was based on a blend of
deterministic solutions including the 00Z ECMWF/12Z GFS.
After day 5, ensembles show general agreement on the large scale
pattern, with the upper trough gradually slowly sliding east,
beginning to break down the northern extent of the upper ridge.
Models/ensemble have trended a bit slower with the process of
breaking down the ridge, however. Differences become quite
significant among deterministic solutions with respect to the
details of individual systems traversing the broader mean trough.
Thus, trended heavily toward the ECENS/GEFS ensemble means during
days 6-8 (Sun-Tue), which supported the idea of another low
pressure system crossing the Aleutians during that time frame, as
the system farther east reaches southern mainland Alaska bringing
a round of increased precipitation coverage/intensity as the
system moves inland and weakens.
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
-Heavy precipitation across portions of the southwest and south
central mainland Alaska coast, Thu, May 23.
-Heavy precipitation across portions of the southwest and south
central mainland Alaska coast, Sat-Mon, May 25-27.
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