Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
621 PM EDT Thu May 12 2022
Valid 12Z Mon May 16 2022 - 12Z Fri May 20 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/Aleutians and an elongated trough over the
Mainland connecting closed upper low/troughs centered over the
Arctic Ocean and eastern Gulf of Alaska. This should persist into
early next week before it may finally begin to weaken and shift
slowly eastward as the pattern begins to break down some and
become less blocky.
Models and ensembles seem in better than average agreement for
much of Alaska and vicinity with the overall pattern evolution
through medium range time scales. 12 UTC GFS/ECMWF solutions in
particular are best clustered with the GEFS/ECMWF ensemble means
days 4-8 and a composite blend tends to mitigate smaller scale
embedded system differences consistent with predictability. An
exception is over the Arctic Ocean where the GFS and ECMWF show
more significant surface low depiction differences over time whose
detail seems correctly marginalized in the blend. The resultant
base forecast along with some manual edits to ensure system
consistency surface/aloft maintains good product continuity in a
pattern with overall above normal predictability.
...Weather and Hazard Highlights...
There are chances for modest precipitation across portions of
mainland Alaska into next week as upper disturbances/surface
fronts work across the area, but the main threat should remain for
any river flooding associated with snow melt and ice jams.
Offshore to the south, a well organized upper low/trough and
associated surface system lingering over the eastern Gulf of
Alaska will favor a periodic focus for light to moderate terrain
enhanced precipitation over Southeast Alaska/Panhandle into
early-mid next week before the system slips southeastward and
loses influence over the region. Overall, a pretty benign
precipitation pattern for the state.
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 slowly works inland next
week.
Schichtel
Hazards:
- Flooding possible across portions of mainland Alaska, Sun-Thu,
May 15-May 19.
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