Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
629 PM EDT Tue May 12 2020
Valid 12Z Sat May 16 2020 - 12Z Wed May 20 2020
Pattern Overview
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An Arctic high will funnel cooler mainland temperatures for much
of the North Slope and Interior. A lead main low will pass through
the Gulf of Alaska, but well south of the Mainland. Several
subsequent lows are expected to pass through the
Aleutians/Southwest AK and emerge into the Gulf this upcoming
weekend through next midweek.
Guidance/Predictability Assessment
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The WPC medium range Alaskan product suite was primarily derived
from a composite blend of reasonably well clustered guidance from
the 12 UTC GFS/ECMWF days 4-7 and the 19 UTC National Blend of
Models in a pattern with above average forecast predictability.
Also included in the composite blend some input from the 12 UTC
ECMWF ensemble mean days 4-7 for smaller scale consistency, but
especially by day 7 into 8 amid growing forecast spread and
uncertainty with embedded weather systems. ECMWF ensembles seem
more in line with the 12 UTC GFS/ECMWF than the 12 UTC GEFS. WPC
continuity in the larger scale flow evolution was reasonably well
maintained.
Weather/Hazard Highlights
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Expect cooler temperatures over a majority of the mainland over
the upcoming week. Above normal readings should decrease in
coverage and become more confined to southern/western areas of the
state while the pattern will gradually become more favorable for
below normal temperatures over northern and eastern areas. Expect
significant precipitation to be fairly limited in coverage during
the period owing to the southern extent of the oceanic lows and
the surface high governing the overall weather pattern for central
and northern sections. A front settling across the southern
mainland may focus some activity at times while light
precipitation may reach northeastern areas next weekend with the
arrival of upper troughing. As the leading Gulf of Alaska system
progresses, expect its track to remain far enough south for only
limited moisture to reach the southeast Alaska Panhandle.
Subsequent organized systems tracking over the western Pacific
should bring moisture and wrapping rainfall Sunday-next midweek
mainly into the Aleutians/Southeast Bering Sea then the AK
Peninsula/Southwest AK. These lows will also offer a maritime
hazard.
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 meteorological 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