Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
407 PM EDT Wed Jun 12 2019
Valid 12Z Sun Jun 16 2019 - 12Z Thu Jun 20 2019
Models have converged toward a somewhat faster progression of the
upper low across the Gulf of Alaska days 4-6 (Sun-Tue), and this
trend was reflected in the latest WPC forecast. Farther north,
models have struggled with the timing/amplitude of arctic
shortwave energy expected to dive south across northwestern Alaska
Mon-Tue, but a blend of solutions should resolve these differences
favorably. Deterministic solutions begin to diverge on the details
of the forecast from Tue onward, but ensemble means suggest that a
broad upper-level mean trough should remain in place from
near/south of the Aleutians east into Southeast Alaska and western
Canada, with the flow farther north reliant on a complex
interaction between westerlies off the Bering Sea/Siberia and
easterlies south of a ridge across the Arctic Ocean, the details
of which are elusive at this point in time. Given these
considerations, the forecast was initially based on a multi-model
deterministic blend (00Z ECMWF/CMC/12Z GFS) during days 4-5, with
a shift to majority ensemble mean weighting from day 6 onward, and
most weight placed toward the more consistent ECENS mean.
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
No significant hazards are expected over Alaska during this
forecast period.
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