Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
644 PM EDT Sat Mar 28 2020
Valid 12Z Wed Apr 01 2020 - 12Z Sun Apr 05 2020
A relatively progressive weather pattern appears set to evolve
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. The evolving pattern will also lead to a
very gradual warming trend, with initially well below average
temperatures across portions of southern/eastern mainland Alaska
slowly moderating at least a bit closer to seasonal norms through
the mid to latter portion of next week (but perhaps remaining
slightly below normal). A leading frontal system should bring
precipitation and gusty winds to the Alaska Peninsula Wed-Thu (day
4-5), while surface high pressure begins to weaken and retreat
across the Interior. The GFS was the preferred solution during
days 4-5, as it has shown perhaps somewhat more consistency than
other guidance, and also remains reasonably well-centered within
the ensemble spread. By late next week, guidance shows general
agreement that a relatively deep low pressure system should take
shape in the Bering Sea. Deterministic solutions show typical
variability for the time range with respect to timing, structure,
and intensity of the system. Consensus among ensemble means is
much better, however, with the ECENS/GEFS/NAEFS all showing a low
deepening across the western Bering Sea Thu night-Fri, and either
approaching the Bering Strait (per the ECENS) or northwestern
mainland Alaska (GEFS/NAEFS) next Sat-Sun. In either of these
scenarios, the surface front south of the low would bring
increasingly widespread precipitation across the Aleutians and
into the western half of mainland Alaska through next weekend,
with some potential for strong gusty winds for coastal locations.
Given the increased spread after day 5, opted to lean much more
heavily toward ECENS/GEFS ensemble means for days 6-8 (Fri-Sun).
Ryan
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