Scientific Forecaster Discussion
Southcentral and southwest Alaska forecast discussion
National Weather Service Anchorage Alaska
440 am akst Sat Jan 31 2015
Analysis and upper levels...
high pressure dominates the area extending across the Bering Sea
and over western parts of Mainland Alaska. However...the high is
weakening as it gradually pushes east. South of the high a deep
low is swinging a front towards the Alaska Peninsula and Gulf. Out
west another low is bringing a weak front to the western Aleutians
as it tracks north.
models are in good agreement in the short and middle terms with the
major features. The only issue is with a triple point low forming
off the front that is approaching the Gulf from the south.
Placement and intensity of the low vary between the models with
the NAM being the strongest and having the western most solution.
Short term forecast southcentral Alaska (days 1 and 2)...
dry weather on tap for the next couple of days with high pressure
building in from the northwest. The only exception to this is
Kodiak where some low level moisture will continue to be pushed
into the island through this evening. Some gap-flow winds will
continue through Sunday then begin to diminish Sunday night as the
ridge axis settles in over southern Alaska. Some patchy fog is
possible in protected areas...probably increasing a little each
night with the ridge overhead.
Short term forecast southwest Alaska (days 1 and 2)...
clear and cold conditions will continue for the Mainland today and
tomorrow. The main forecast problems will be how much wind from
just off the surface are allowed to mix down to the...affecting
temperatures. Gusty winds will relax on Sunday as the gradient
weakens. A slight warming trend will continue but light winds and
cloud free sky at night will still allow for temperatures to fall
off near zero or into the negatives.
Short term forecast Bering Sea/Aleutians (days 1 and 2)...
a storm force front approaches the Alaska Peninsula today. Light
rain should run up to the Pacific side of the peninsula
tonight...but quickly fall apart as the front weakens. High
pressure builds over the Bering Sea on Sunday keeping
precipitation and clouds at Bay.
Long term forecast (days 3 through 7)...
the forecast for Monday will remain very similar to current
conditions as ridging over the south Mainland will slowly begin
weakening. This will keep temperatures near normal throughout the
Mainland...with continued offshore flow along the Gulf Coast and
southwest coast. Starting late Monday the first in a series of
upper level troughs will quickly dive through the Mainland...dragging
with them progressively colder air over the Mainland that look to
continue through the end of next week. Most of the state will remain
under a split flow regime into the middle of next week with the
Arctic troughs diving through the Mainland...ridging over the
Mainland...and a persistent upper level low just south of the
Aleutians. This pattern will keep the bulk of the precipitation in
the aor confined from the eastern Aleutians to Kodiak Island.
The main challenge in the long term forecast is trying to
determine the exact track of the Arctic troughs. The models have
had great agreement...but with poor run to run consistency in trending
significantly eastward with these features over the last 2 days.
For example...the upper trough currently projected to move into
the Canadian Yukon on Wednesday was expected to move through the
Bering Sea with equally good model agreement just 48 hours ago.
Exactly how far east these features travel will be critical to
determining how much cold air move into the region. For this
reason temperatures in much of the long term forecast remain only
slightly below normal...but there is a potential for these
temperatures to be much colder into late next week.
Marine...gale 127 128 131 132 138 172.
Synopsis and model discussion...dk
southwest Alaska/Bering Sea/Aleutians...ml