Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
221 PM EDT Fri Jun 15 2018

Valid 12Z Tue Jun 19 2018 - 12Z Sat Jun 23 2018

The medium range period begins on Tuesday with a large upper low
over the eastern Bering Sea and its associated surface low over
southwestern Alaska, and a quasi-stationary frontal boundary
situated near the Brooks Range.  The guidance is hinting at a
weaker surface low pivoting northward towards the south-central
coast by midweek and possibly a third and stronger system entering
the Gulf of Alaska by the end of the forecast period next Saturday
as depicted by the CMC and GFS.  The ECMWF is not on board with
this third system and has more indications of high pressure over
that region. 

In terms of sensible weather impacts, widespread rain and high
mountain snow is likely for the coastal areas of southern Alaska
owing to deep southerly flow from the northern Pacific.  This
moisture is forecast to reach portions of the Interior on Tuesday
and Wednesday, albeit lighter than the coastal areas.  Mild
temperatures are expected during this forecast period with 60s
commonplace across the lower elevations and 50s closer to the
coast.  It will still be cold north of the Brooks Range to the
Arctic coast, however highs are expected to be above freezing
area-wide.

The forecast for the Alaska domain during the medium range period
next week was mainly derived from a composite blend of the 6Z
GFS/GEFS mean and 00Z ECMWF/EC mean. Consistent with previous WPC
continuity, the first part of the forecast (through Wednesday) was
derived with a higher percentage of the deterministic GFS/ECMWF
and then greater weighting to the GEFS/EC means for Thursday and
beyond.   

D. Hamrick

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