Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
221 PM EST Fri Nov 08 2019
Valid 12Z Tue Nov 12 2019 - 12Z Sat Nov 16 2019
Models show relatively good consensus that a deep surface low
should approach the Alaska Peninsula Tue-Wed. Timing and some
remaining intensity differences among deterministic and ensemble
solutions make for moderate confidence, with ensemble means
showing central pressure values 15-20 mb higher than their
respective deterministic solutions. Given the trend, incorporated
a blend of the latest deterministic guidance (ECMWF/CMC/GFS) into
the forecast for days 4-5 (Tue-Wed), which resulted in a downward
trend in the central pressure of the system compared to the
previous forecast (although still not quite as low as shown in the
latest deterministic solutions). This low pressure system could
produce a variety of impacts, including the potential for high
winds and significant waves along the coast. As this system moves
inland and weakens Thu-Fri, the upper-level energy, along with
additional arctic shortwave energy arriving from the north, are
forecast to linger across western mainland Alaska in the form of
an upper low through late next week. Model solutions agree on this
general concept although solutions differ as to the specific
intensity of the upper low. South of this upper low, a stream of
small scale but quick moving shortwaves are expected to cross near
the Aleutians and toward the Gulf of Alaska. Spread increases
through time, but some consensus was noted among ensemble means
that another low pressure system should approach southern mainland
Alaska by next Fri night or Sat, associated with one of the more
significant aforementioned shortwaves. Given gradually increasing
spread, a trend to heavier weighting of ECENS/GEFS ensemble means
was shown during days 6-8 (Thu-Sat).
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
- High winds across portions of mainland Alaska, Tue-Wed, Nov
12-Nov 13.
- Much above normal temperatures across portions of northern
Alaska, Mon-Wed, Nov 11-Nov 13.
- High significant wave heights for coastal portions of mainland
Alaska and the Aleutians, Tue-Wed, Nov 12-Nov 13.
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