Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
751 PM EDT Tue Apr 19 2022
Valid 12Z Sat Apr 23 2022 - 12Z Wed Apr 27 2022
...Guidance/Predictability Assessment...
Extended range period over Alaska begins with a deep surface low
moving into the Gulf, and weakening with time. The latest models
are showing some timing/placement differences on this low (the GFS
is quicker to weaken/shift into western Canada late period), but a
general model blend seems to give a good middle ground for now on
this feature. Farther upstream, a surface low will cross the
Kamchatka Peninsula next weekend, moving into the western Bering
Sea by late Monday. After this, models show uncertainty on the
eventual track of this feature. The 12z GFS weakens this low over
the northern Bering Sea, while the 12z CMC and ECMWF break a new
low off this parent low and move it over the Aleutians and into
the Gulf of Alaska by the middle of next week. The ensembles are
varied on this feature resulting in a rather washed out mean
solution, but at least would suggest low pressure in the Gulf
around Tues-Wed next week, rather than ridging like the 12z GFS is
showing. By next Wednesday, another low looks to enter the Bering
but the models show quite a bit of uncertainty on timing and
strength of this. For the later periods, the WPC blend
incorporated more of the ensemble means to help mitigate the
differences, with some contribution from the deterministic CMC and
ECMWF for added system definition. Despite increasing uncertainty
in the guidance compared to yesterday, todays forecast remained
fairly consistent with yesterdays WPC forecast.
...Overview Weather/Hazard Highlights...
Moisture will direct northward along the attendant cold front of
the low pressure system into the Gulf this weekend to support
enhanced and locally heavy precipitation (lower elevation
rain/mountain snow) across parts of the Southern Coast and
eventually eastward into the Panhandle this weekend and early next
week as the system weakens. Parts of the Aleutians may also see
precipitation associated with uncertain low and cold front
progressions. Precipitation could return across the Southern
Coast/Panhandle region by mid next week, but depending on the next
low pressure system into the Gulf. Elsewhere, much of the Interior
and North Slope regions should remain dry, with temperatures
mostly above normal and trending warmer through the period.
Southern regions, from the Aleutians to the Panhandle, should
remain near or below average owing to increased clouds and
precipitation.
Santorelli
Hazards:
- Heavy precipitation across portions of the Alaska and Kenai
Peninsulas, Sat, Apr 23.
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