Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
604 PM EST Sun Dec 08 2019
Valid 12Z Thu Dec 12 2019 - 12Z Mon Dec 16 2019
Upper ridging will meander over the Arctic Ocean which will favor
reinforced/reinvigorated troughing to its southwest out of the
Bering Sea. The storm track will be fairly progressive but not
without wound-up/robust surface systems. The first system of
interest will be a dying low near Kodiak Thu per the consensus of
the 12Z ECMWF/UKMET/Canadian as the GFS remains the only one to
move a coherent surface low from the occlusion into Bristol Bay.
Weak system will slide underneath the dissipating surface low into
southern BC as another system moves through the Bering
east-southeastward through the Aleutians. Consensus from the
models (even the 12Z GFS there) sufficed until about late
Saturday. Thereafter, the ensembles favored low pressure in the
eastern Bering/Bristol Bay while the deterministic models (except
the GFS) took low pressure south of the Aleutians. Though some
triple point development may ultimately warm the front's
orientation, opted to maintain a simpler progression with the old
parent low weakening over the eastern Aleutians with the triple
point moving into the Gulf. Ensembles were steady with timing for
this cycle. Yet another system may move into the western Bering
around next Monday but with little agreement seen in the models as
of yet.
Temperatures will largely be near/above average with a southerly
component to the flow and near/above average heights and low level
temperatures (850mb temperature anomalies about +1 to +2 sigma).
There should be a trend back toward more typical December values
by next week over at least the interior. Precipitation will be
focused along the coast from Southcentral to the Panhandle around
the lead weakening occlusion and trailing upper trough. Some
rainfall could be heavy along the coast ending Thursday before a
drier pattern between systems. Expect a renewed precipitation
uptick next Sun/Mon.
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