Alaska Extended Forecast Discussion
NWS Weather Prediction Center College Park MD
657 PM EST Wed Feb 26 2025
Valid 12Z Sun Mar 02 2025 - 12Z Thu Mar 06 2025
...A fairly deep cyclone could bring enhanced precipitation and
gusty winds into the southern coastal section of mainland Alaska
midweek next week...
...Overview...
Multiple disturbances rotating about a large cyclonic gyre in the
vicinity of northeastern Siberia and the Bering Sea will be
directed against a strong and persistent upper ridge extending
across mainland Alaska through much of the medium-range period.
Ensemble means show good agreement that a larger and fairly deep
cyclone will eventually erode and undercut the ridge over the Gulf
of Alaska by midweek next week to bring increasing chances of
heavy precipitation into the southern coastal sections of mainland
Alaska along with anomalously mild conditions.
...Guidance Evaluation and Preferences...
Much of the uncertainty regarding today's medium-range guidance
for the Alaskan domain today is centered around the timing of a
cyclone that is projected to slide from west to east along the
Aleutians early next week, possibly reaching the Alaska Peninsula
to the Gulf of Alaska by Day 8 Thursday. There is one general
theme displayed by the model guidance today--the GFS/GEFS
continues to yield a cyclone track that is noticeably west of the
ECMWF/EC mean solution, with the Canadian/CMC mean only slightly
farther west of the EC solutions. The preference is to lean
toward the EC/CMC mean cluster since their solutions from recent
runs have been more consistent with one another when comparing
with the consistency of the GFS/GEFS cluster. The EC-AIFS does
not appear to offer helpful insights into the cyclone track as the
model outputs continue to exhibit noticeable run-to-run
inconsistency across the Alaskan domain.
The WPC forecast package for Alaska today was based on a consensus
blend leaning toward the ECMWF/CMC cluster, with 50% from the 12Z
ECMWF and 00Z/12Z EC mean, 25% from the 12Z GFS/GEFS, and 25% from
the 12Z CMC/CMC mean. The main differences seen on today's
forecasts versus yesterday's forecasts were regarding the timing
of the interaction and merging of smaller-scale disturbances south
of the Alaska Peninsula on Day 4-6. Difference in the timing of
the larger cyclone near the eastern Aleutians on Day 7 was minimal
when comparing with yesterday's Day 8 forecast.
...Weather/Hazards Highlights...
Moderate coastal rain and higher elevation snow associated with
the remnants of a northeast Pacific cyclone should continue to
diminish this weekend as the cyclone is forecast to dissipate in
place, but with some light precipitation possibly extending into
southwestern mainland. Another modestly strong cyclone will
likely follow in its wake and approach the Peninsula from the
south early next week before it gradually dissipates. This
disturbance will help sustain the light to locally moderate
precipitation across Kenai Peninsula and eastward along the
Southcentral coast. Both features may bring some moisture farther
east, reaching mainly into the northern portion of the Panhandle.
Meanwhile, periods of some light snow can be expected to spread
northward across the western mainland near a wavy front through
midweek as the front evolves into a stationary inverted trough.
Thereafter, the system being forecast to track from the
northwestern Pacific into the Aleutians early-mid week should
become the dominant feature by Wednesday, eventually increasing
winds across a broad area over the Pacific and Bering Sea plus
spreading organized precipitation across the Aleutians and then
supporting an easterly fetch of moisture into the Alaska
Peninsula. It appears that heavy precipitation is possible by the
latter part of next week over the typically-favored areas of the
Kenai Peninsula and into the eastern Peninsula as a fairly deep
cyclone is forecast to track generally from west to east passing
south of these locations.
Expect temperatures to be above normal over a majority of the
state through the period along with a gradual warming trend from
this weekend into early next week. There should be decent
coverage of plus 10-20F or greater anomalies. The North Slope
will be an exception, as Arctic high pressure supports somewhat
below normal readings that may linger into Saturday before the
general warming trend pushes anomalies above normal. Portions of
the lower elevations of southern mainland could see afternoon
temperatures well into the 40s by midweek next week. Meanwhile, a
wavy front pushing across the western mainland may lead to some
cooling over western areas from the weekend into early next week
but temperatures should remain above normal.
Kong
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