Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
754 PM EDT Sat Mar 26 2022
Valid 12Z Wed Mar 30 2022 - 12Z Sun Apr 03 2022
...Overview...
Guidance continues to show an active pattern across the Bering
Sea/Aleutians/North Pacific with episodes of enhanced
precipitation and winds, while flow aloft likely trends toward
mean ridging from western Canada into Mainland Alaska. There is
improving confidence today that the two regimes will interact
between the Alaska Peninsula and Kenai Peninsula, leading to a
period of locally heavy precipitation focused by one or more
fronts/waves after midweek. Lighter precipitation should extend
farther east to the Panhandle as well. A strong system may track
into the Aleutians/Bering Sea next weekend but with some
uncertainty for details.
...Guidance/Predictability Assessment...
Early in the period, guidance appears to have gravitated toward
intermediate ideas between yesterday's contrasting GFS and
majority cluster solutions. Parent low pressure near the
Aleutians may stay fairly far south as GFS runs had been
indicating but there may still be lingering over the Bering Sea as
well, reflecting prior majority. Meanwhile there is still a
decent signal for frontal waviness to track over or near the
Alaska Peninsula/southwestern mainland. Over the past day the CMC
has trended somewhat in this direction from its prior progressive
solution (still a bit east of the GFS/ECMWF), but remains on the
fast side with the wave's front that lifts through the Gulf of
Alaska.
Farther upstream most solutions continue to hint at progressive
North Pacific energy that may produce or reinforce low pressure
along or south of the eastern Aleutians/Alaska Peninsula around
Friday-Saturday before dissipating. There is still a variety of
detail possibilities, tempering confidence in any particular
evolution.
Operational models have done a lot of shuffling around for the
potentially deep system that may reach the Aleutians/Bering Sea by
next weekend, while the ensemble means have been fairly stable
thus far. The past two ECMWF runs are fairly close to the means
after some earlier runs were on the fast side. On the other hand
the GFS has become quite weak and suppressed with the initial
western Pacific energy/surface wave, though it has sufficiently
low heights aloft over the Bering Sea to yield some low pressure
there as well. The 12Z UKMET strays fast by the end of its run
while the CMC holds the low west of the means. Preference is to
stay closest to the means/ECMWF until a more confident alternative
arises.
The model/mean majority maintains the general theme from yesterday
that somewhat ill-defined flow over the mainland as of midweek
should then evolve more toward ridging that extends from western
Canada. The current consensus has generally trended a bit
stronger with this ridge over the past 24 hours. Models do offer
the potential for some energy within the trough to the northeast
to cut into the ridge toward the weekend, most likely over the
North Slope if that occurs.
Today's forecast started with a blend of 12Z models and then
transitioned toward the past two ECMWF runs plus the 12Z GEFS/00Z
ECMWF means late. This reflected detail refinements early in the
period and then helped to maintain the best continuity possible
mid-late period.
...Weather/Hazard Highlights...
There is gradually improving consensus that by Thursday Pacific
waviness lifting north along a front initially anchored by
Aleutians/Bering Sea low pressure should focus a period of
enhanced moist flow into southern coastal areas. Currently expect
the heaviest precipitation to be centered along the eastern Alaska
Peninsula to Kenai Peninsula. Some of this precipitation with
lesser totals should extend farther east to the southeastern coast
and Panhandle. Upstream lows/fronts may promote lingering
activity along the southern coast through the weekend but with
lower amounts than with the Thursday episode. The potential still
exists for a vigorous storm to track into the Aleutians/Bering Sea
next weekend with organized precipitation and strong winds, though
with enough spread in the guidance to keep confidence at moderate
levels.
The temperature forecast is fairly consistent from yesterday.
Expect most of the southwestern half of the mainland to see above
normal temperatures. Anomalies for highs should be greatest over
far western areas while well above normal lows may be more
widespread over the south and west. The rest of the mainland
should see a mix of above/below normal readings, with some below
normal temperatures most likely over the North Slope/northeast
corner of the mainland. Expect the Panhandle to see below normal
highs and near to above normal lows.
Rausch
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