Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
349 PM EDT Thu Oct 11 2018

Valid 12Z Mon Oct 15 2018 - 12Z Fri Oct 19 2018

...Heavy precipitation likely across southeastern Alaska early
next week...

...Guidance and Predictability Assessment...

A powerful mid/upper-level low with height departures around 1.5
sigma below climatology will track across the eastern Aleutians
eventually weakening upon approach into far southwestern Alaska.
The accompanying deep surface cyclone is expected to weaken as
this occurs while persistent warm advection continues across the
northeastern Pacific. The synoptic-scale pattern does not move
appreciably until mid-week as the upper low opens up and
translates downstream. Shifting focus to the south and west, a
pair of features emerge on the map by late next week. Amplified
flow west of the Aleutians as well as over the northeast Pacific
will play key roles in the upcoming forecast. Some forecast
solutions, particularly the past few runs of the GFS are extremely
deep with sub 960-mb pressures by 19/1200Z for the latter system.
Initially, solutions were well clustered supporting a heavier use
of operational models. A general balance of the 12Z GFS/00Z ECMWF
with their respective means were utilized through Day 6/October 17
before moving toward a more ensemble based approach.


...Weather Highlights/Hazards...

Initially, the weather will be quite active along the
south-central coast of Alaska toward the panhandle region. Strong
pressure gradients in response to the deep surface low over the
Aleutians could afford wind gusts into the 40 to 60 knot range
along the southern Alaska coastline. Farther east, a substantial
plume of Pacific moisture will take aim at southeastern Alaska
with a lengthy period of moderate/locally heavy precipitation.
Through early next week, some of the 12-hour totals via the
GFS/ECMWF runs favor 1 to 2 inch amounts. The intensity should
come down a bit by mid week before possibly ramping up late in the
period in response to the next projected deep low. Otherwise, cool
and cloudy conditions should persist over much of the state given
the upper trough in place. It is forecast to be quite chilly over
northern Alaska with lows and highs struggling to escape the 20s.


Rubin-Oster

WPC medium range Alaskan products including 500mb, surface
fronts/pressures progs and sensible weather grids can be found at:

http://www.wpc.ncep.noaa.gov/alaska/ak_5dayfcst500_wbg.gif
http://www.wpc.ncep.noaa.gov/alaska/akmedr.shtml
http://www.wpc.ncep.noaa.gov/alaska/ak_5km_gridsbody.html