Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
414 PM EDT Tue May 08 2018

Valid 12Z Sat May 12 2018 - 12Z Wed May 16 2018

...Guidance/Predictability Assessment and Preferences...

At the onset of the forecast, a broad upper low should be in the
process of crossing far west-central Alaska with the remnant
circulation continuing to lift toward the polar region. In its
wake, models have been consistent the past few cycles in driving a
longwave trough across the north-central Pacific to south of the
Aleutians by Day 7/8, May 15/16. While the guidance varies in
placement, the signal is quite strong which warrants greater use
of operational models during the period. This will ultimately help
build heights downstream across the Gulf of Alaska into the middle
of next week. Confidence in the pattern is actually higher later
in the period given the increasing amplitude of the flow regime.
With some certainty in the forecast, was able to maintain a
mixture of the 12Z GFS/00Z ECMWF out to Day 8/May 16 while
gradually increasing influences from the 06Z GEFS mean and 00Z
ECMWF/NAEFS ensemble means.


...Weather/Threat Highlights...

The largest temperature changes are expected across central Alaska
by the early to middle part of next week in response to a building
upper ridge. Expect highs to near the mid 60s in some locations
while locations in close proximity to the Arctic Ocean struggle to
get above freezing each day.

Initially, precipitation chances will be the higher end with the
approach of the upper low through the state. Such a threat should
continue into the weekend before subsiding a bit into early next
week. Gradually increasing moisture advection in advance of the
next trough will bring a threat for precipitation to the Aleutians
and eventually locations farther downstream. This should also be
accompanied by an increase in wind fields over the region,
particularly over the south-central Alaskan coast by Day 7/8, May
15/16.


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

Rubin-Oster