Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
635 PM EDT Fri Mar 13 2020
Valid 12Z Tue Mar 17 2020 - 12Z Sat Mar 21 2020
...Overview and Guidance/Predictability Assessment...
A series of potentially powerful Pacific systems will lift through
a highly unsettled Aleutians and Bering Sea and tend to work
inland into the Interior/North Slope then Arctic Ocean, breaking
through a lead upper level mean ridge position. There is potential
for the development of quite deep lows with well organized frontal
structures that would focus winds and widespread and
enhanced/widespread precipitation. Temperatures will warm across
the Interior/North Slope next week, but remain cold enough to
support widespread heavy snows, with a particular risk for
northwest Alaska with strongest low approach and shearing over the
region later next week.
Meanwhile underneath, additional system trough/jet energies will
break eastward through the southern portion of a lead main upper
ridge position next week over the Gulf of Alaska in a pattern with
more modest precipitation potential for
southwest/southern/southeast Alaska.
...Weather Highlights/Threats...
The WPC Alaskan medium range product suite valid Tuesday-Thursday
was mainly derived from a composite blend of reasonably well
clustered guidance from the 12 UTC GFS/ECMWF, GEFS/NAEFS/ECMWF
ensemble means and the 19 UTC National Blend of Models (NBM).
Forecast continuity and predictability seem above normal during
this period. Forecast spread increases with embedded systems in
the 7/8 day timeframe, so it seems prudent to rely on more
consistent and seemingly reasonable GFS/NAEFS and ECMWF ensemble
mean guidance and the NBM at these longer time frames along with
manual edits to depict system strength/integrity consistent with
near average predictability.
Schichtel
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
Hazards:
- Heavy precipitation across portions of the Alaska Peninsula,
Mon, Mar 16.
- Heavy precipitation across portions of the coastal sections of
southern Alaska, Tue, Mar 17.
- Heavy snow across portions of northwestern Alaska, Thu-Fri, Mar
19-Mar 20.
- High winds across much of western and northwestern Alaska,
Wed-Fri, Mar 18-Mar 20.
- High winds across the Aleutians, Tue-Wed, Mar 17-Mar 18.
- Much above normal temperatures across much of western and
northern Alaska, Mon-Fri, Mar 16-Mar 20.
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