Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
707 PM EDT Mon Mar 30 2020
Valid 12Z Fri Apr 03 2020 - 12Z Tue Apr 07 2020
A relatively progressive weather pattern appears likely across
Alaska and the North Pacific during the extended forecast period.
A strong upper-level jet along the northern periphery of a
building upper-level ridge axis near the date line and along the
southern periphery of a broad region of cyclonic flow across
eastern Siberia will result in an increasingly active storm track
across the Bering Sea. Ensembles show general agreement that this
relatively progressive flow regime should persist across Alaska
and the Bering Sea through the extended forecast period (and
beyond), with relatively strong shortwaves traversing the North
Pacific jet spaced 2-3 days apart.
A leading frontal system should bring precipitation and gusty
winds to portions of southern mainland Alaska and the Alaska
Panhandle on Fri (day 4). Deterministic solutions showed quite a
bit of variability and inconsistency throughout the extended
forecast period, making it difficult to prefer a single model
solution for the forecast across Alaska and surrounding waters. A
blend of the ECMWF/UKMET along with the ECENS/GEFS ensemble means
represented a reasonable consensus during days 4-5, as a deep low
pressure system moves across the western/central Bering Sea. After
that, deterministic spread becomes quite large, by Sun (day 6) as
the weakening low pressure system crosses mainland Alaska, and a
new low develops farther south across the northern Gulf of Alaska
on Mon (day 7). This system appears likely to bring a period of
relatively widespread precipitation to mainland Alaska Sun-Mon,
with some potential for gusty winds along the Bering Sea coast. By
Mon and into Tue, as the low develops in the Gulf, expect
precipitation to increase across the Alaska Panhandle. Given the
increased guidance spread during days 6-8, a majority ensemble
blend (ECENS/GEFS ensemble means) was used during that time frame.
Ensemble means showed much better overall consensus than did
deterministic solutions.
Ryan
Hazards:
- Heavy precipitation across portions of mainland Alaska, Thu, Apr
2.
- Much above normal temperatures across portions of mainland
Alaska, Thu-Fri, Apr 2-Apr 3.
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