Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
309 PM EDT Sun May 05 2019
Valid 12Z Thu May 09 2019 - 12Z Mon May 13 2019
The models and ensembles still show a blocking pattern through
this week with a high amplitude Bering Sea trough extending across
the Aleutians into the north Pacific and resultant high amplitude
ridge across the northeast Pacific and southeast Alaska.
Towards the end of next week, the models start to diverge with the
timing and placement of vortices rotating around the Bering Sea
trough and resultant placement of lows in the Bering/northern
Pacific and adjacent southwestern AK.
The 00z ECMWF/00z ECMWF Ensemble Mean/06z GEFS Mean show a cyclone
developing over the northeast Pacific Thu that then moves north
onshore later Fri to early Sat. The 12z GFS lagged several hours
behind the 06z GFS/00z ECMWF/respective GEFS/ECMWF Ensemble Means,
so the 12z GFS was not included in the blend, with the majority
cluster preferred.
The next area of interest would be a wave developing over the
northern Pacific
around 12z Fri south of the Aleutians. There was sufficient
clustering on the location among the 00z ECMWF/yesterday's 12z GFS
/00 ECMWF Ensemble Mean/06z GEFS Mean/NAEFS Mean to use a blend of
these solutions Fri and Sat as the system moves northeast. By 12z
Sun there is potential for this cyclone to be as far north as
either the upper Aleutians and/or Kodiak Island. At 12z Sun the 00
ECMWF Ensemble Mean and 00z NAEFS Mean/06z GEFS Mean cluster west
of the operational ECMWF low pressure center location.
Temperatures will be warmer than normal over southeast AK through
most of the week due to the strong upper ridge and corresponding
warm temperatures that remain well above normal.
Precipitation will focus over the southern coastal areas Thu-Fri,
with low pressure moving onshore fostering showers moving inland.
Locally heavy rain may be possible in upslope locations.
Petersen
Bullet points from the WPC Days 3-7 Hazards chart can be found at:
https://www.wpc.ncep.noaa.gov/threats/threats.php
WPC medium range Alaskan products including 500mb, surface
fronts/pressures progs and sensible weather grids can also be
found at:
https://www.wpc.ncep.noaa.gov/alaska/ak_5dayfcst500_wbg.gif
https://www.wpc.ncep.noaa.gov/alaska/akmedr.shtml
https://www.wpc.ncep.noaa.gov/alaska/ak_5km_gridsbody.html