Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
618 PM EDT Thu Apr 23 2020
Valid 12Z Mon Apr 27 2020 - 12Z Fri May 01 2020
...Guidance/Predictability Assessment...
The overall pattern across Alaska during the extended forecast
period continues to demonstrate average to slightly above average
predictability during the early part of the forecast period (days
4-5), and with predictability quickly decreasing during days 6-8.
The 12Z ECMWF/CMC showed relatively good consensus with the
ensemble means during days 4-5 (Mon-Tue), 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
(Wed) and beyond, increasing ensemble means (particularly the
ECENS) through time were used to account for the increasing
spread. Most guidance continues to show a low pressure system
crossing the Aleutians and moving into the western/central Bering
Sea by midweek, with a triple point low potentially developing and
deepening south of the Alaska Peninsula by Thu-Fri, although
spread becomes increasingly large with respect to the specific
details of the system structure and timing.
...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, a couple arctic
mid-upper level troughs/impulses will work over the North Slope
and the Interior through early next week, bringing below average
temperatures to portions of the Interior. A relatively weak
mid/upper-level ridge axis is forecast to build across the
Interior by the middle to latter portion of next week, gradually
moderating temperatures some. As a result, 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-Wed, Apr
26-Apr 29.
- High winds across portions of the Aleutians, Tue-Wed, Apr 28-Apr
29.
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