Scientific Forecaster Discussion
Southcentral and southwest Alaska forecast discussion
National Weather Service Anchorage Alaska
336 PM akst Wednesday Dec 17 2014
Analysis and upper levels...
there is an upper level low in the southwest Gulf of Alaska. There
is another low over the northern Bering Sea. There is a low
centered south of the Kamchatka peninsula...and associated with it
is a 200 knots jet at around 35 to 40 degrees north latitude poking
into the middle Pacific (around 170 degrees east longitude). There is
an upper level ridge beginning to build over southern Alaska.
the numerical models are not in very good agreement today. They
quickly begin to diverge on solutions for a complex low south of
the Aleutians (24 to 36 hours into the forecast) and also with the
low in the Gulf of Alaska as it becomes complex. Some of the
models struggles probably are related to the 200 knots jet...where
small perturbations in the flow can quickly develop into large
differences. Therefore forecast confidence is below normal today.
Short term forecast southcentral Alaska (days 1 through 3)...
there is a weak front over south central Alaska that will
dissipate tonight as ridging builds ahead of the low approaching
from the southwest. This low (currently over the southwest gulf)
will push east into the south central Gulf tonight...turn
northward on Thursday...then push westward to the western
Gulf/Alaska Peninsula where it will settle in through Saturday. A
strong front associated with this low will push into the north
Gulf tonight then stall off the Gulf Coast. This is where the
models begin to disagree...but essentially a triple point low will
form on the front Thursday night then move northward through
Friday. For Friday night and Saturday...various surface low
centers will be spinning around the main upper low.
Short term forecast southwest Alaska (days 1 and 2)...
the remainder of today will be fairly quiet across the Mainland as
the area remains between weather systems. Higher clouds will
continue to stream overhead from the south tonight as a frontal
boundary swings up toward the Alaska Peninsula associated with a
low pressure system in the North Pacific. Some weak disturbances
in the flow could bring areas of rain mixed with snow to mainly
southern areas of interior Bristol Bay along with northerly winds
of 10 to 20 miles per hour. Temperatures will continue to run above normal
without a deep Arctic air mass in the interior. The pattern holds
through Friday with any potential precipitation chances staying
in interior Bristol Bay.
Short term forecast Bering Sea/Aleutians (days 1 and 2)...
the Bering Sea also currently sits between three systems. A
frontal boundary close to the Alaska Peninsula will keep rain
showers in the forecast...but cloud cover should be on the
decrease tonight. Most of the Bering Sea sits under an unstable
showery regime left over by the last system. These conditions
will taper tonight as a new front forms south of the chain
bringing an increase in easterly winds and snow.
Long term forecast (days 4 through 7)...
the main story is that the upper level pattern will become more
progressive next week. The low over the western Gulf/Alaska
Peninsula will be pushed eastward on Sunday and Monday as a large
upper low develops over the western Bering Sea. Strong westerly
flow aloft will progressively push east until all of the Bering
Sea and southern Alaska are involved by Wednesday night. The wpc
forecast favors the 00z European model (ecmwf) and 00z European model (ecmwf) ensemble mean...with
some 12z GFS sprinkled in.
Marine...gales...119 120 127 130-132 138 139 150 175-178