Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
447 PM EDT Mon May 06 2019
Valid 12Z Fri May 10 2019 - 12Z Tue May 14 2019
The models and ensembles still show a blocking pattern through
this week into the weekend 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 Gulf of AK and 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 remains slower than
the 00z ECMWF/respective GEFS/ECMWF Ensemble Means/Canadian global
model, so the 12z GFS was under weighted 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. The spread of models and
ensembles actually increased a bit from yesterday, so a blend of
the 00z ECMWF/12z GFS /00 ECMWF Ensemble Mean/06z GEFS Mean/NAEFS
Mean/Operational Canadian was used Fri through the weekend as the
system moves northeast.
By 12z Sun there is potential for another cyclone to develop over
the northern Pacific and have potential to reach the Aleutians
early next week.
The 12z GFS/00z ECMWF had good timing agreement while the Canadian
global had an intermediate timing in between the GFS and the
faster/further east ECMWF Ensemble Mean. A blend of these
solutions was used until better agreement develops.
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. Gale force winds
are forecasts over the western Gulf of AK with the Thu night to
early Fri cyclone.
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