Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
354 PM EDT Thu May 17 2018

Valid 12Z Mon May 21 2018 - 12Z Fri May 25 2018

Lead upper low will slowly fill in the Gulf of Alaska next week as
another system moves through the southern Bering Sea to the
central Aleutians Wed-Fri. The models show better than average
agreement with the initial system and a blend of the 12Z GFS with
the 00Z ECMWF/UKMET/Canadian served as a good starting point. This
takes the front quickly inland on Monday as it rides up and over
the upper ridge to the east. Lingering boundary to the south will
slowly head eastward into British Columbia. Models diverge on the
handling of the Bering system next Tue-Thu with the 00Z UKMET much
quicker than the consensus. 12Z GFS was close to the agreeable 06Z
GEFS/00Z ECMWF ensemble mean with the 00Z ECMWF just a bit slower.
A blend of these four kept good continuity. That system should
slide eastward toward the western Gulf but perhaps dissipate as
heights attempt to rebuild over the Panhandle later next week.
Trailing upper trough may support a secondary front next Thu/Fri
wrapping around the low.

Temperatures will be near to below average, especially over south
central areas with abundant cloudiness/showers. Some areas of
above average temperatures will be found through the interior.
Rain and mountain snow will focus across southern/coastal areas
into the Panhandle early in the week with modest precipitation
over the eastern interior relative to normal as the dissipating
occlusion passes through. Second system will spread rain across
the Aleutians starting Tuesday through most of the week.

Fracasso


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