Scientific Forecaster Discussion
fxak69 pafg 162318
Northern Alaska forecast discussion
National Weather Service Fairbanks Alaska
318 PM akdt Mon Oct 16 2017
Models...trending toward colder pattern next couple days.
Initialized well against the 16/18z surface analysis. Run to run
solutions remain very good in the short term and midrange. Some
significant discrepancies in the extended periods over the
Aleutians that will need to be worked out over time. Models have
handled the low dropping out of the high Arctic similarly with not
much spread in location or strength. Temperature guidance is not
very good, and in particular is not handling low temperatures well
since many areas remain snow free on the ground. Will utilize a
blend of the solutions for precipitation and will lean on
continuity for temperatures but need to make some changes to match
Aloft...at 500 hpa...stacked low that has been over the Gulf of
Anadyr the last few days continues to weaken and will eventually
merge with the low dropping out of the Arctic. The low dropping
out of the Arctic is 100 nm north of Banks Island at 495 dam and
will move southwest to be Over Point Barrow by Thursday morning at
496 dam, and over the Seward Peninsula by Friday afternoon at 500
dam. Ridging west of 160w in the Arctic and over the Chukchi Sea
will continue to be pushed west as the low moves southwest and
will be west of 180 by Tuesday evening. Weak ridging over the
southwest Mainland with a 525 dam center will continue to weaken
and move east tonight and merge with ridging over the Gulf of
Alaska. A shortwave associated with the Arctic low is moving over
the Arctic coast this afternoon and will continue to rotate around
the low. A second shortwave will move to the coast on Tuesday
afternoon, and a third on Wednesday morning. A 513 dam low over
the central Aleutians will move rapidly east through Thursday
then dissipate over the southeast Panhandle. At 850 hpa...zero
isotherm south of the state. The low over the Canadian archipelago
continues to spin colder air south and the -10 isotherm lies from
Dawson yt to Anaktuvuk Pass to Cape Lisburne this afternoon, and
will lie from Dawson yt to Bettles to Teller and west by Tuesday
afternoon. By Wednesday morning it will lie from Chalkyitsik to
Monday morning. By Tuesday morning it will lie almost entirely
south of out forecast area. The -20 isotherm approaches the
central and eastern Arctic coast Wednesday.
Surface...weak high pressure over southwest Mainland and eastern
interior will weaken and pull back over the northeast Pacific and
Yukon territory. Weak high pressure over the western Brooks range
will pull back to the west. A weak trough over the Seward
Peninsula extends east over the upper Yukon Flats and will
continue to expand as broad area of troughing develops between the
991 mb low near Banks Island, and the 975 mb low over the western
Aleutians. The low near Banks Island will remain stationary
through the evening, then move north Tuesday rotating west then
south to be Over Point Barrow by early Thursday morning. A rapidly
developing low 500 nm north of Point Barrow will move to 150 nm
north of Point Barrow by Tuesday morning at 998 mb and over the
central Arctic plain by Tuesday evening. High pressure west of
160w and over the Chukchi Sea will weaken and be pushed west as
the low drops out of the Arctic to the coast. The low in the
western Aleutians will move to 100 nm south of Cold Bay by Tuesday
morning, and into the northeast Pacific Tuesday night. The low
over Banks Island will continue to move south after moving over
the coast Thursday and will be over Kotzebue Sound by Thursday
afternoon at 993 mb.
Arctic coast and Brooks range...could be very interesting Tuesday
as the low sitting high in the Arctic moves to the central coast.
Winds will increase from Point Barrow west and winter weatehr
advisories remain in place for zones 201 and 202. Conditions will
be improving on the eastern Arctic coast by morning. Snowfall
amounts 2 to 4 inches but may be up to 6 inches depending on
development of the low and how much moisture it will pick up. The
open water factor, no sea ice within 500 nm of most of the Arctic
coast, will have unknown impact on the moisture values. Northwest
winds 5 to 15 becoming north 10 to 30 mph with the strongest winds
between Point Lay and Point Barrow.
West Coast and western interior...quiet period overall. Some
sprinkles or flurries with mostly cloudy conditions. Patchy fog
along the rivers in the morning. Winds generally variable to 10
mph through Tuesday. Temperatures slightly cooler.
Central and eastern interior...cloudy with some flurries this
evening, then some light snow developing early Tuesday morning
with up to 2 inches of snow possible. Heaviest snow will be in the
White Mountains and upper chena river basin east of Two Rivers.
Patchy fog. Generally light winds. Temperatures will continue the
cooling trend with lows falling to around 20 and high around 30 in
Fairbanks and vicinity. Coldest temperatures will be north of the
Yukon river where lows will fall to zero to -10. Much cooler
temperatures for the end of the week through the weekend across
Extended forecast for days 4 to 7...Saturday through Monday models
remain in good agreement. They are currently having issues with
the potential of an extra tropical system being caught in the flow
and moving rapidly over the Aleutians.
Coastal hazard potential days 3 and 4...none.
Winter Weather Advisory for akz201-akz202-akz204.
Heavy freezing spray warning for pkz240-pkz245-pkz505-pkz510.
Small Craft Advisory for pkz240-pkz245.