Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
547 PM EDT Fri Apr 17 2020
Valid 12Z Tue Apr 21 2020 - 12Z Sat Apr 25 2020
...Overview and Guidance Evaluation and Weather/Threats
Highlights...
The main weather threats should be for maritime interests next
week, with benign flow for much of Alaska. System potential and
lingering guidance uncertainties focus to the south of the
Aleutians and the Alaskan Peninsula as organized/slow evolving
lows settle over the region and reform into the Gulf of Alaska. In
this pattern moisture will tend to reach the Southern and
Southeast Alaskan coasts as main cyclones spin offshore. A lead
wave could bring a higher chance of precipitation into southern
and southeastern Alaska through midweek, with best potential for
heavier amounts over favored Southeast terrain in onshore flow.
Guidance is more agreeable farther inland over the state. An
amplified upper ridge built up through the Interior over the short
range will be replaced by a unsettling mean weakness aloft through
medium range time scales. This will moderate the current warm
spell in a pattern with modest precipitation potential that may
focus in vicinity of the weakness/low aloft and a lingering and
wavy surface front.
Overall, a composite blend of 12 UTC GFS. 12 UTC GEFS/ECMWF
ensemble means and the 19 UTC National Blend of Models seems to
produce a good forecast starting point for the day 4-8 period. Of
the deterministic models, the GFS seems best clustered with the
ensemble means and provides some enhanced detail consistent with a
pattern with average to above average predictability. Manual
adjustments were then applied to produce sufficient offshore
system depths consistent with upper support, but artificially
weakened by the blend process. This Alaskan office collaborated
forecast strategy maintains great WPC continuity.
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: No significant hazards are expected over Alaska during
this forecast period.
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