Scientific Forecaster Discussion
Southcentral and southwest Alaska forecast discussion
National Weather Service Anchorage Alaska
410 PM akst sun Mar 1 2015
Analysis and upper levels...
there is a large and somewhat negatively tilted ridge of high
pressure over southern Alaska that extends southward to just off
the West Coast of Canada. There is an elongated trough over the
western Bering with a north-to-south oriented front across the
central Bering and central Aleutians. There is another low south
of the eastern Aleutians with a southeast-to-northwest front
stretching from the southwest Gulf into the Alaska Peninsula and
eastern Aleutians. This is a highly amplified pattern...but shows
signs of being transient in nature (i.E. It should not last very
the numerical models are in good agreement for the short term
portion of the forecast. There are of course some minor
differences in the details...but over-all the forecast confidence
is a bit higher than normal.
Short term forecast southcentral Alaska...
ridging that sits over the southcentral will allow for fog to
redevelop tonight throughout much of the southcentral. The fog
will start to get cleared out from a front approaching from the
south. This front will move through Kodiak and will make it to
the Kenai Peninsula tomorrow...bringing another surge of warm air
and precipitation to the region. The biggest question will be if
there is enough warm air to avoid the risk of freezing rain inland.
It currently looks like coastal locations will go safely over to
regular rain...but that locations along Cook Inlet will remain
colder longer so there will still be the potential for freezing
rain with the overrunning warm air. The biggest potential is late
Monday night and early Tuesday morning for the western Kenai to
the mat valley. Fortunately all precipitation for these inland
areas is expected to be light.
Short term forecast southwest Alaska...
the colder temperatures in the southwest Alaska region will
remain in the Kuskokwim Delta and lower Kuskokwim valley. The
North Pacific low continues on track to move across the central
Aleutians and by Monday morning be located just southwest of the
Pribilof Islands. An associated weather front will be positioned in
the eastern Bering Sea. This will bring warmer temperatures and
rain to the coastline of southwest Alaska before spreading inland.
This is now expected to result in a period of light freezing rain
for the Kuskokwim Delta and the lower Kuskokwim valley. As a
result...freezing rain advisories have been issued for both
locations. The Bristol Bay region has warmer temperatures and
will likely see isolated pockets of light freezing rain briefly
before temperatures rise safely above freezing. By Wednesday
another weather front will be in the eastern Bering Sea. This will
bring onshore flow and warmer temperatures to the southwest Alaska
Short term forecast Bering Sea/Aleutians...
a North Pacific low developing south of the central Aleutians
moves into the central Bering Sea by Monday morning. This system
will be located just north of the Pribilof Islands by Monday
afternoon and an associated weather front in the eastern Bering
Sea. This will result in gale force winds along the southwest
Alaska coastline with widespread rain spreading into the region.
On the backside of this low the central to western Bering Sea
will have northwesterly winds with scattered snow showers through
Monday. This system moves north into the Bering Strait by Tuesday
morning. A storm force North Pacific low moves near Kamchatka
peninsula by late Monday night with an associated weather front
approaching the western Aleutians. This frontal boundary will
move just west of the Pribilof Islands by Wednesday morning
bringing more showery precipitation. Meanwhile...the western
Aleutians/Bering Sea will have gusty westerly winds with a
mixture of rain and snow showers during this time frame.
Long term forecast (days 3 through 7)...
a progressive upper level pattern characterized by zonal flow
near 60n latitude will keep active weather over much of the
region through next weekend as a series of systems track eastward
through the Bering Sea into Mainland Alaska. The first of these
systems will depart to the east by middle week but will quickly be
followed by a sharp shortwave trough that will traverse the
Mainland late Thursday into Friday. A deeper trough then looks to
move over the Mainland during the weekend. This active pattern
will keep a chance of precipitation over a wide swath of the
Bering and southern Mainland throughout much of the next
week...with precipitation type remaining a challenge across the
Mainland as daytime temperatures hover near freezing. This will
likely result in a mix of rain and snow for many locations.
public...Freezing Rain Advisory 152 155
marine...gale 130 131 138 139 177 178
heavy freezing spray 185
Synopsis and model discussion...bl
southwest Alaska/Bering Sea/Aleutians...period