Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
646 PM EDT Sun Jun 13 2021
Valid 12Z Thu Jun 17 2021 - 12Z Mon Jun 21 2021
...Guidance/Predictability Evaluation...
The WPC Alaskan medium range product suite was primarily derived
from a blend of well clustered guidance of the 12 UTC GFS/ECMWF,
12 UTC GEFS/NAEFS/ECMWF ensemble means and the 19 UTC National
Blend of Models Day 4-6 (Thursday-Saturday). The 12 UTC GFS/ECMWF
are better clustered than yesterday, so applied higher blend
influence in this period. The 12 UTC ECMWF is better clustered
with the 12 UTC GEFS/NAEFS/ECMWF ensemble means for days 6/7, so
that blend was then used as a basis for the WPC forecast. The
larger scale pattern evolution and storm track still seems solid
in guidance. However, given the recent run to run model
sensitivity/continuity issues with many flow embedded systems, the
newly improved forecast spread probably needs to be maintained for
more model runs before bolstering confidence too much with these
small-mid scale features.
...Weather/Threats Highlights...
A stable, shielding and warming mean upper ridge is expected to
settle over much of the Interior and North Slope for much of this
forecast period. Meanwhile, a persistent and active storm track
will progress near/just south of the Aleutians and into the Gulf
of Alaska. In this flow, a complex and uncertain series of
potentially deep lows and frontal systems may focus quite
unsettled maritime and periodic rains and winds into southwest
Alaska, the Alaskan peninsula and southern and southeast Alaska.
Schichtel
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