Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
936 PM EDT Sat Aug 28 2021
Valid 12Z Thu Sep 02 2021 - 12Z Mon Sep 06 2021
...Heavy rainfall possible for portions of the southern Coast
region during the middle part of next week...
...Pattern Overview and Model Guidance...
The models are still handling this evolution fairly well during
the extended period given the typical spread on specific details.
A combination of the 12Z ECWMF/CMC/GFS has been the preferred
starting point recently and still seems to be the path solution.
The inclusion of the ensemble means increase through the middle
and later periods. During the extended period ridging will be in
place over much of the interior and southeast and will shift
eastward as a upper trough progresses across the Aleutians into
the Gulf of Alaska. As this happens an upper low will begin to
settle in over the Bering Sea and a series of short waves will
pass through the base of the trough, spinning up a couple of
surface fronts that will track across the Aleutian Chain and into
southern coast/Alaska peninsula. Meanwhile, to the north, a strong
polar vortex and associated mid-level westerly flow will be in
place across the Arctic and North Slope early in the week before
heights begin to rise again across the region and the Polar Vortex
retreats to the north.
...Sensible Weather...
Temperatures will be below seasonal average across the northern
and central parts of the state near a draped boundary. High
pressure will keep much of the interior and parts of the panhandle
drier. By Friday, much of the state could have daily temperature
near or above normal underneath of amplified upper-level ridging.
Rain is expected to track from the peninsula to the southern
Mainland as a low pressure system lifts into the eastern Bering
Sea, as it's attendant cold front drifts eastward through the
Gulf. During this time, there will be periods where the rain will
be moderate to heavy, especially from upper portions of the
peninsula, Kodiak Island, Kenai and the Cook Inlet into Friday.
The heavier rain may reach into far southeast Alaska late Friday
and through the weekend. These areas may also experience gusty
winds.
Campbell
Hazards:
- Heavy rain across portions of southern Alaska, Wed-Thu, Sep
1-Sep 2.
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