Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
247 PM EDT Sat Apr 06 2019
Valid 12Z Wed Apr 10 2019 - 12Z Sun Apr 14 2019
Deep troughing well southwest of the Aleutians on Wednesday (500mb
height anomaly around -3 stnd dev) will lift northeastward into
the Bering as ridging builds ahead of it into the Gulf and eastern
interior portions of Alaska. This will help strengthen a system
well down into the 960s mb, reaching peak intensity as it crosses
the Aleutians. Strong winds 40-50 kts are likely. Upper pattern
will largely split the system into the decaying parent low in the
Bering and triple point low with the frontal system into the Gulf,
spreading rain/snow to the AKPen, Southcentral, and eastward into
the Panhandle. The North Slope and eastern interior will stay
largely quiet and precipitation-free.
The ensembles were mostly aligned through the period and were
close to continuity, so used that as a starting point for the
forecast. The 00Z ECMWF was closest among the deterministic
models, followed by the Canadian and GFS in various stages. The
evolution of the multi-shortwave conglomerate early in the week
will act to modulate how the deeper system tracks into the Bering
Sea, but opted to maintain a somewhat simpler frontal analysis for
now. Next system of interest would be next weekend out of the
central Pacific and across the western or central Aleutians and
into the Bering Sea. 00Z ECMWF/GFS and 12Z GFS/FV3 GFS were either
close to or surrounded the ensemble consensus. Upper ridging
should still hold in place from the Yukon northwestward into the
Beaufort Sea.
Fracasso
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