Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
357 PM EDT Mon May 28 2018

Valid 12Z Fri Jun 1 2018 - 12Z Tue Jun 5 2018

The extended forecast period over the Alaska domain begins on
Friday with more deterministic model differences than usual for
that time range, and these differences increase going into the
weekend.  The 00Z CMC is well to the east of the model and
ensemble clustering over eastern Siberia with the closed upper
low, and the upper ridge over the Aleutians is much more
progressive.  The surface low over the northeast Pacific is
forecast to slowly weaken as it reaches the British Columbia
coast, with the GFS and ECMWF to the southeast of the ensemble
means.  By Saturday, the guidance is indicating a stronger system
approaching the western and central Aleutians, with the UKMET and
ECMWF being the stronger solutions, and the GFS and CMC the faster
and weaker models.  By Sunday, the ECMWF is closer to both the
GEFS and EC means whilst deeper than the GFS and CMC.  Towards the
end of the forecast period, the GFS tries to take this low
underneath a much strong upper ridge (compared to the model
consensus) over the Alaska mainland and has limited ensemble
support for this scenario.  Given the large scale differences by
the second half of the forecast period, confidence is below
average and this suggests maintaining some continuity from
yesterday's forecast.

In terms of sensible weather, much of the mainland should be
mainly dry with isolated showers during the afternoon.  The best
prospects for rain will be for the Aleutians as the strong storm
system slowly approaches from the western Bering Sea by the
weekend, along with gusty southerly winds ahead of the cold front.
 Temperatures will be gradually moderating north of the Brooks
Range and including the Arctic Coast, with highs easily reaching
into the 40s for highs.  Pleasantly warm conditions are expected
for the Interior with widespread highs in the 60s and 70s for the
lower elevations.

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


D. Hamrick