Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
716 PM EDT Wed May 11 2022
Valid 12Z Sun May 15 2022 - 12Z Thu May 19 2022
...Overview and Guidance/Predictability Assessment...
The upper flow pattern across Alaska over the next week looks to
remain quite amplified/blocky as highlighted by strong ridging
over the Bering Sea and an elongated trough from the Mainland into
the Gulf of Alaska containing high latitude system energies from
the Arctic. One shortwave looks to drop through the western
Mainland next weekend helping to reinforce a large closed
trough/low over the Gulf. This low looks to meander into early
next week before it may finally weaken and get pushed east as the
pattern begins to break down some and become less blocky.
Despite lingering differences in the details, a composite blend of
the latest 12z deterministic models seemed to offer a good
starting point for the first half of the forecast period, although
the 12z CMC was notably stronger/faster with energy rounding the
top of the ridge across eastern Siberia into the Arctic. Bigger
uncertainties begin to arise later in the period regarding
reinforcing energy into the Gulf low and also systems moving
across the Mainland. There are also differences regarding how
quickly the low in the Gulf weakens and moves into western North
America. The GFS/CMC are a little faster than the ECMWF and
ensemble means. Given these uncertainties which continue to vary
in model run to run continuity, the WPC forecast trended more
towards the ECENS/GEFS ensemble means by the second half of the
period, with some inclusion of the GFS and ECMWF for a little
added definition to systems. This forecast plan maintains decent
WPC Alaskan product continuity.
...Weather and Hazard Highlights...
Increased light and periods of moderate precipitation are likely
to organize and shift southward across portions of Mainland Alaska
this weekend into next week as upper disturbances and several well
organized surface fronts work across the area. There is some
threat for stronger and gusty winds, mainly over the western
mainland, as pressure gradients tighten with system passages. Some
river flooding is expected to be ongoing associated with snow melt
and ice jams in some locations across the Mainland as well.
Offshore to the south, regeneration through the weekend and into
early-mid next week of a well organized upper low/trough and
associated surface system position over the Gulf of Alaska will
also favor a periodic focus for moderate and terrain enhanced
precipitation over Southeast Alaska/Panhandle.
Temperatures across much of the Mainland into at least early next
week will remain below normal, with much below normal values in
some places, especially parts of northern Alaska as a deeper
shortwave drops in through the region. Temperatures may moderate
some again around Tuesday-Wednesday, though still below normal.
Parts of Western Alaska and the Peninsula may finally get above
normal though as the Bering Sea ridge begins to move into the
region.
Santorelli
Hazards:
- Flooding possible across portions of mainland Alaska, Sat-Sun,
May 14-May 15.
Additional 3-7 Day Hazard Information can be found on the WPC
medium range hazards outlook 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