Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
256 PM EDT Sat Jul 13 2019
Valid 12Z Wed Jul 17 2019 - 12Z Sun Jul 21 2019
One upper low will wobble around the Arctic Ocean as another
slowly exits the Gulf through the Panhandle. This leaves much of
the interior in weak ridging aloft that will be replaced by
incoming troughing on the south side of the Arctic upper low late
next week. The models/ensembles show good agreement in the
northern areas but less agreement over the Pacific. The recent GFS
runs were much stronger with a surface low pressure along a
baroclinic zone to the north of an upper and sfc high in the
mid-latitudes (between Alaska and Hawai'i) as the ensembles
generally keep the boundary flat. The flatter scenario is
preferred given the setup with seemingly little room to develop so
robustly. The 00Z ECMWF was closest to the ensemble consensus and
was used to add detail to the forecast with the 00Z GEFS mean and
00Z ECMWF ensemble mean to smooth out some timing differences.
Farther north, the 00Z ECMWF may be too aggressive with height
falls next weekend with the incoming trough into northwestern
Alaska. Blend with the means tempered that in the blend but
building ridging into the Bering next weekend could support
something like the ECMWF (at least 10-20% of the ensembles were at
least as aggressive as the ECMWF).
Scattered showers and a few thunderstorms will be possible through
much of the forecast period, particularly across the interior and
over the higher terrain along the wavy boundary. Coverage north of
65N will increase as the upper trough moves through. Cooler than
average temperatures are expected to the north. Upper low and
onshore flow will keep the rain chances high over the Panhandle
with near to below average temperatures.
Fracasso
Additional 3-7 Day Hazard information can be found on the WPC
medium range hazards chart 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