Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
640 PM EDT Wed Apr 22 2020
Valid 12Z Sun Apr 26 2020 - 12Z Thu Apr 30 2020
...Guidance/Predictability Assessment...
The overall pattern across Alaska during the extended forecast
period continues to demonstrate average to slightly above average
predictability, particularly early in the forecast period. The 12Z
ECMWF/CMC showed relatively good consensus with the ensemble means
during days 4-5 (Sun-Mon), and a blend of these solutions was used
as a forecast starting point during that time frame. This blend
maintained excellent forecast continuity, with a couple relatively
deep low pressure systems rotating northward into the Gulf of
Alaska during that time frame. Starting on day 6 (Tue) and beyond,
a blend of the ECMWF along with increasing ECENS/GEFS ensemble
means through time was used, to account for gradually increasing
spread. Most guidance continues to show a low pressure system
crossing the Aleutians and moving into the western/central Bering
Sea Tue/Wed, although spread becomes increasingly large with
respect to the specific details of the system structure and
timing. The aforementioned blend resulted in a new triple point
low that is forecast to develop south of the Alaska Peninsula by
next Thu.
...Weather/Threats Highlights...
Two low pressure systems expected rotate over the Gulf of Alaska
to off Southeast and Southern Alaska through early next week will
bring an increased threat for high winds across portions of the
Panhandle, along with locally heavy precipitation. Potential for
precipitation/winds should increase across portions of the
Aleutians toward the middle of next week in association with the
Bering Sea low pressure system. Farther inland over the state, a
couple arctic mid-upper level troughs/impulses will work over the
North Slope and the Interior over the coming week, bring below
average temperatures through the weekend to portions of eastern
mainland Alaska. The air mass across the Interior and the North
Slope will remain quite dry through the forecast period, with
little in the way of appreciable precipitation.
Ryan
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:
- High winds across portions of the Alaska Panhandle, Sun-Mon, Apr
26-Apr 27.
- High winds across portions of the Aleutians, Tue-Wed, Apr 28-Apr
29.
- Much below normal temperatures across portions of mainland
Alaska, Sat-Sun, Apr 25-Apr 26.
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