Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
158 PM EDT Sun Mar 31 2019
Valid 12Z Thu Apr 04 2019 - 12Z Mon Apr 08 2019
Models and ensembles reasonably agree that a positively tilted
upper trough across western and northern AK will deepen as a piece
of energy slowly drops down its axis into the Bering Sea. The
cooling temperatures aloft associated with the strengthening mid-
to upper-level trough will slowly transition clear skies early on
to cloudy conditions by next weekend across mainland AK and
rainfall in southeast AK and the panhandle is expected to slowly
increase in amounts and coverage from Friday through next weekend.
Ridging is expected to persist on either side of the trough
across Siberia and western Canada.
Guidance is not in perfect agreement with how the upper low drops
down the trough, but is reasonably close; no significant outliers
were noted. The WPC product suite was primarily derived from a
composite blend of the 00z bias-corrected NAEFS mean, 00z ECMWF
ensemble mean, 00z ECMWF, 06z/12z GFS, and 00z Canadian guidance.
This pattern will hold the main Pacific storm track south of
Alaska/the Gulf of AK from Thursday through next Monday. The
potential phasing of systems passing around the base of the upper
trough could lead to more northward and deeper low pressure
systems closer to Alaska sooner or later, which needs to be
watched on later runs. Precipitation will be mainly limited to
parts of the Aleutians closer to the storm track, along with the
AK Panhandle and southern coastal Alaska.
Roth/Schichtel
Bullet points from the WPC Days 3-7 Hazards chart can be found 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