Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
526 PM EDT Wed Mar 18 2020
Valid 12Z Sun Mar 22 2020 - 12Z Thu Mar 26 2020
...Overview and Guidance/Predictability Assessment...
In the wake of a departing Bering Sea system late in the week, the
latter portions of the weekend into early next week is likely to
feature upper level ridging and surface high pressure, especially
across southern Alaska. A fast moving storm system across northern
mainland will bring widespread high chances of precipitation. By
Day 7-8 (Wed-Thu), model guidance trends toward more troughing as
a shortwave approaches the western mainland with the approach of a
deeper surface low that is just beyond the current forecast
period.
...Weather Highlights/Threats...
Model agreement was average to slightly above average for days 4-5
where an equal blend of the deterministic guidance was used (12Z
ECMWF/GFS/UKMET/CMC). Beyond that time frame, the latest ECMWF/CMC
showed better run to run consistency while the 12Z GFS seemed to
be racing ahead of the ensemble means somewhat. Thus, considerably
less GFS was used for day 6-8 with increasing weights of the ECENS
ensemble mean each day through day 8. This should help mitigate
the less predictable small scale variances later in the forecast
period while maintaining some WPC forecast continuity.
Taylor
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 snow across portions of mainland Alaska, Sat, Mar 21 and
Mon-Tue, Mar 23-Mar 24.
- Much above normal temperatures across portions of mainland
Alaska, Sat-Tue, Mar 21-Mar 24.
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