Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
658 PM EDT Tue Apr 07 2020
Valid 12Z Sat Apr 11 2020 - 12Z Wed Apr 15 2020
...Overview and model guidance...
Strong upper ridging over northeastern Russia (+4 sigma 500mb
height anomaly later this week) will meander between 110-130E as a
second area of ridging builds into the eastern Gulf/Panhandle.
This will favor troughing in between, mostly over the Bering, as
several shortwaves and/or weakly closed lows lift northeastward up
and over the ridge. Strong jet off central Asia will set up a
split flow east of the Dateline which has led to some run-to-run
changes in the guidance. The 12Z GFS was a bit quicker to lift a
system out of the mid-latitudes compared to the ECMWF/Canadian,
and was more eager to break down or at least punch through the
ridge in the Gulf around next Tue, but otherwise was within the
ensemble spread. However, put more weight into the ECMWF/Canadian
which clustered a bit better near the ECMWF ensemble mean, which
formed an increasing weight in the blend. To the west, a more
muddled view was evident with multiple systems in the fray. With
little predictability, 50% weighting of the ECMWF ensemble mean
helped to mute some features that can only be refined at a shorter
lead time.
...Weather/Threats Highlights...
Lead system lifting across the eastern Aleutians/AKPEN this
weekend will bring modest to perhaps locally heavier rain to
coastal areas and favored upslope regions of Kodiak Island.
Otherwise, rain/snowfall will be on the lighter side over the rest
of the state as high pressure very slowly retreats into Canada.
Along the North Slope, a warm front may bring some scattered snow
to the area before it moves into the Beaufort Sea. This will also
bring in milder air to especially northern areas with temperatures
perhaps 10-20 degrees above normal. Over southeastern areas,
temperatures will be below normal as high pressure to the
north/northeast maintains a chillier easterly flow.
Fracasso
Hazards:
- Heavy precipitation across portions of mainland Alaska, Mon-Tue,
Apr 13-Apr 14.
- Much above normal temperatures across portions of mainland
Alaska, Sun-Tue, Apr 12-Apr 14.
- Much below normal temperatures across portions of mainland
Alaska, Fri, Apr 10.
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